ORIGINAL ARTICLE
Insulin gla gine use and b eas cance isk: Associa ions wi h cumula i e
exposu e
Paul J. H. L. Pee e s
a
,Ma loes T. Bazelie
a
,Hube G. M. Leu kens
a
,Anssi Au inen
b
,Tjee d P. an S aa
a,c
,
F ank de V ies
a,d,e,
and Ma ie L. De B uin
a
a
U ech Ins i u e o Pha maceu ical Sciences, U ech Uni e si y, The Ne he lands;
b
School o Heal h Sciences, Uni e si y o Tampe e,
Tampe e, Finland;
c
Heal h eResea ch Cen e, Fa Ins i u e o Heal h In o ma ics Resea ch, Uni e si y o Manches e , Manches e , UK;
d
Medical Cen e Maas ich and School o Public Heal h and P ima y Ca e (CAPHRI), Maas ich Uni e si y, Maas ich , The Ne he lands;
e
MRC Li ecou se Epidemiology Uni , Uni e si y o Sou hamp on, Sou hamp on, UK;
Depa men o Clinical Pha macy and Toxicology,
Maas ich Uni e si y Medical Cen e , Maas ich , The Ne he lands.
ABSTRACT
Backg ound: This s udy was aimed o assess he isk o b eas cance associa ed wi h exposu e o insu-
lin gla gine in women wi h ype 2 diabe es and e alua e whe he he pa e n o isk concu s wi h he
hypo hesized end o an inc ease in isk wi h longe du a ion o use, aking in o accoun p e ious
cumula i e exposu e o o he ypes o insulin.
Me hods: We pe o med a es ospec i e coho s udy (2002–2013) in he Clinical P ac ice Resea ch
Da alink among adul emale pa ien s wi h a i s e e insulin p esc ip ion (n¼12 468). Time-dependen
exposu e measu es we e used o assess associa ions wi h du a ion o use o : (1) o he insulin ypes
be o e gla gine was i s p esc ibed (i.e. among swi che s); and (2) o gla gine du ing ollow-up.
Analyses we e pe o med sepa a ely o insulin-na
€
ı e gla gine use s and pa ien s swi ched o gla gine.
Cox p opo ional haza ds models we e used o de i e p- ends, haza d a ios (HR) and 95% con idence
in e als (CI) o b eas cance associa ed wi h gla gine use.
Resul s: Du ing 66 151 pe son yea s, 186 b eas cance cases occu ed; 76 in gla gine use s (3.0/1000
yea s) and 110 in use s o o he insulins (2.7/1000 yea s). Among insulin-na
€
ı e women, no associa ion
wi h cumula i e gla gine use was obse ed (p- end ¼0.91), e en a e 5 yea s (HR ¼1.06, 95% CI
0.48–2.33). Among swi che s, a linea end wi h yea s o p io exposu e o o he insulins was ound
(p- end ¼0.02). An inc eased isk was obse ed in gla gine use s wi h ex ensi e (>3 yea s) pas expos-
u e o o he insulins (HR ¼3.17, 95% CI 1.28–7.84). A non-signi ican end wi h cumula i e gla gine
exposu e was ound among swi che s (p- end ¼0.24).
Conclusions: Exposu e o gla gine was no associa ed wi h an inc eased b eas cance isk in insulin-
na
€
ı e pa ien s. Exposu e o o he insulins p io o he s a o gla gine appea s o be ele an when
s udying b eas cance isk associa ed wi h gla gine use.
ARTICLE HISTORY
Recei ed 9 Oc obe 2015
Re ised 9 Feb ua y 2016
Accep ed 10 Feb ua y 2016
In women, ype 2 diabe es is associa ed wi h an inc eased
isk o b eas cance [1,2]. In 2009, a numbe o obse a ional
s udies eme ged ha linked he use o long-ac ing insulin
gla gine o an inc eased cance incidence among women
wi h ype 2 diabe es, in pa icula b eas cance [3–5]. Since
hen, ea men wi h insulin gla gine has been s udied in en-
si ely o i s possible associa ion wi h an inc eased b eas
cance isk [6,7]. Howe e , obse a ional s udies among insu-
lin use s a e complica ed by he ac ha all insulins o some
ex en ac as a g ow h s imula ing ac o [8].
Human insulin ac s as a g ow h p omo ing agen , s imula -
ing b eas cance cell g ow h and inhibi ing apop osis in i o
[9]. Di e ences in mi ogenic po ency be ween human insulin
and insulin analogs on b eas cance cells ha e been shown
in i o [8,10]. Insulin gla gine speci ically appea s o ha e
an inc eased mi ogenic po ency [8,10], possibly ela ed o
i s inc eased a ini y o he insulin-like g ow h ac o -1 ecep-
o [11]. O e all, esul s om cell s udies indica e a cell
g ow h s imula ing e ec , a he han a ca cinogenic e ec
[12]. Consequen ly, he isk o b eas cance is expec ed o
inc ease wi h longe du a ion o exposu e.
Howe e , he majo i y o epidemiological s udies con-
duc ed did no assess ends in b eas cance isk wi h du -
a ion o gla gine use. O he mo e de ailed second gene a ion
s udies, only i e assessed cance isk in ela ion o cumula-
i e exposu e measu es [13–17]. All o hem e alua ed du -
a ion o gla gine use among insulin-na€
ı e use s sepa a ely
and only one o he i e s udies obse ed a signi ican
inc eased b eas cance isk associa ed wi h high cumula i e
exposu e o gla gine [14]. Howe e , all s udies lacked su i-
cien ollow-up o obus ly es ima e cance isk beyond h ee
yea s o cumula i e du a ion o use [13–17]. The e o e, u he
CONTACT M. L. De B uin [email p o ec ed] Depa men o Pha macoepidemiology and Clinical Pha macology, U ech Ins i u e o Pha maceu ical
Sciences, U ech Uni e si y, Uni e si ei sweg 99, 3584 CG U ech , The Ne he lands
Supplemen al da a o his a icle can be accessed he e.
ß2016 The Au ho (s). Published by In o ma UK Limi ed, ading as Taylo & F ancis G oup
This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion-NonComme cial-NoDe i a i es License (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/),
which pe mi s non-comme cial e-use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed, and is no al e ed, ans o med, o buil upon in any way.
ACTA ONCOLOGICA, 2016
VOL. 55, NO. 7, 851–858
h p://dx.doi.o g/10.3109/0284186X.2016.1155736
s udy o b eas cance isk wi h long- e m gla gine use
(>3 yea s) emains necessa y.
O he wo s udies ha included p e alen insulin use s
who swi ched o gla gine, one obse ed an inc eased b eas
cance isk a e a leas i e yea s o cumula i e gla gine use
[13]. The o he did no ind an associa ion wi h du a ion o
use, bu was unable o s udy e ec s o long- e m gla gine use
due o a median du a ion o gla gine use o 1.2 yea s [14].
Bo h s udies de e mined exposu e o gla gine a baseline
(in en ion- o- ea ) and we e limi ed by le - unca ed da a,
which esul ed in misclassi ica ion o du a ion o exposu e
and po en ial unde es ima ion o pas exposu e o o he insu-
lins p io o he swi ch o gla gine. Mo eo e , nei he s udy
was able o de e mine how he du a ion o non-gla gine insu-
lin use be o e coho en y modi ies he e ec o gla gine use.
The aim o ou s udy was o assess he isk o b eas can-
ce associa ed wi h exposu e o insulin gla gine in women
wi h ype 2 diabe es and e alua e whe he he pa e n o isk
concu s wi h he hypo hesized end o an inc ease in isk
wi h longe du a ion o use, aking in o accoun p e ious
cumula i e exposu e o o he ypes o insulin.
Me hods
Sou ce o da a
Da a we e ob ained om he Clinical P ac ice Resea ch
Da alink (CPRD), which comp ises elec onic medical eco ds
om B i ish gene al p ac i ione s since 1987 [18]. The accu -
acy and comple eness o CPRD da a ha e been well alida ed
in p e ious s udies [19]. Cu en ly, CPRD includes app oxi-
ma ely 7% o he o al UK popula ion [18]. The p o ocol o
his s udy was app o ed by CPRD’s Independen Scien i ic
Ad iso y Commi ee.
S udy popula ion
Fo his e ospec i e coho s udy, we used a ‘new use ’ design
wi h inciden insulin use s. All women (18 yea s) wi h a leas
one p esc ip ion o any ype o insulin in CPRD du ing he
inclusion pe iod we e eligible. To ensu e a minimal ollow-up
pe iod o app oxima ely h ee yea s be ween coho en y and
he end o da a collec ion (1 Oc obe 2013), he inclusion pe iod
s e ched om 1 Sep embe 2002 – he ma ke ing da e o gla -
gine in he UK – o 31 Decembe 2010. The index da e was
de ined as he da e o he i s eco ded p esc ip ion o any
ype o insulin wi hin he inclusion pe iod. On he index da e, all
subjec s we e equi ed o ha e a leas one yea o up- o-s and-
a d pa ien his o y in CPRD wi hou any eco ded his o y o
insulin use o imp o e he alidi y o he ‘new use ’ design.
Pa ien s conside ed o ha e ype 1 diabe es we e excluded.
These we e pa ien s wi hou any use o non-insulin an idiabe ic
d ugs (NIADs) in he yea p io o coho en y who: 1) had a
eco ded diagnosis o ype 1 diabe es be o e coho en y; o
2) we e unde 30 yea s o age a coho en y. Subjec s wi h a
his o y o b eas cance a baseline we e also excluded. All sub-
jec s we e ollowed om he index da e un il he ou come o
in e es , end o da a collec ion, da e o mig a ion ou o he
CPRD popula ion, o dea h, whiche e came i s .
Exposu e o insulins
We used a ime-dependen design (Figu e 1) o de ine expos-
u e. Fo all pa ien s, he ollow-up pe iod a e he index da e
was di ided in o disc e e 30-day in e als. Exposu e o gla -
gine (‘any use’) was hen de ined as a p esc ip ion o gla -
gine on he s a da e o a any ime be o e he s a o each
in e al. Pa ien s wi h a p esc ip ion o non-gla gine insulin
(i.e. any insulin ype excep gla gine) a coho en y could
become exposed du ing ollow-up i a p esc ip ion o gla -
gine was eco ded (‘swi che s’). Cu en exposu e o gla gine
and non-gla gine insulins was de ined as a p esc ip ion on
he s a da e o in he h ee mon hs p io o he s a o
each 30-day in e al.
In a s epwise manne , we added ime-dependen cumula-
i e measu es o du a ion o use o : (1) gla gine du ing ol-
low-up; and (2) non-gla gine insulins be o e he ini ia ion o
gla gine he apy. In a inal model (3), we s udied b eas can-
ce isk associa ed wi h cumula i e du a ion o gla gine use
sepa a ely among insulin-na€
ı e gla gine use s and use s o
gla gine wi h p io use o o he insulin ypes (Figu e 1).
Cumula i e du a ion o use calcula ions we e based on he
numbe o days o ‘cu en exposu e’.
Du a ion o use o gla gine du ing ollow-up was de e -
mined a he s a o each 30-day in e al and classi ied as
‘0–1 yea s’, ‘1–3 yea s’, o ‘>3 yea s’ (Figu e 1a), based on he
o al numbe o days o cu en exposu e o gla gine.
Consequen ly, cumula i e exposu e o gla gine could only
inc ease o emain s able o e ime.
In swi che s, cumula i e numbe o days o pas exposu e
o non-gla gine insulins was calcula ed a he s a da e o
gla gine ea men . He e, we di e en ia ed be ween insulin-
na€
ı e pa ien s a he s a o gla gine ea men , and swi ch-
e s wi h a cumula i e du a ion o pas exposu e o non-gla -
gine insulins o ‘0–3 yea s’ and ‘>3 yea s’ (Figu e 1b).
In ou inal model, we pe o med sepa a e analyses ega d-
ing associa ions wi h du a ion o gla gine exposu e du ing ol-
low-up among insulin-na€
ı e pa ien s and p e alen insulin
use s swi ched o gla gine (Figu e 1c). In all models, we quan-
i ied he isk o b eas cance associa ed wi h gla gine use as
compa ed o ‘ne e use’ o gla gine; as he s udy was pe -
o med among insulin use s, pe son ime on gla gine was
compa ed o pe son ime on o he insulins.
S udy ou come
All subjec s we e ollowed up o he occu ence o a i s
medical diagnosis o b eas cance in CPRD (see
Supplemen al Table A o he used medical codes, a ailable
online a h p://www.in o maheal hca e.com). Comple eness
o case asce ainmen o b eas cance in CPRD is high as
compa ed o he na ional cance egis y da a [20]. A ecen
s udy ound a conco dance a e o 89.8% wi h cance egis-
ies and a subsequen 6.4% o he eco ds we e in ag ee-
men wi h hospi al eco ds o dea h ce i ica es [20].
Co a ia es
Models we e adjus ed o po en ial con ounde s in a ime-
dependen manne . Age was de e mined as he yea
852 P. J. H. L. PEETERS ET AL.
di e ence be ween calenda yea and yea o bi h a he
s a o each 30-day in e al. A his o y o cance o he han
b eas cance (o non-melanoma skin cance ) and oopho ec-
omy was de e mined as a medical diagnosis a any ime
be o e he s a o each in e al. Smoking s a us (yes o no)
and alcohol use (yes o no) we e de e mined a coho en y
and subsequen ly upda ed du ing ollow-up a he s a o
each in e al. Cu en use o comedica ion (i.e. ho mone
eplacemen he apy, s a ins, me o min, sul onylu eas, and
gli azones) was de e mined as a p esc ip ion in he pas 180
days p io o he s a o each in e al. Fo body mass index
(BMI) and HbA
1c
, he mos ecen eco d be o e he s a o
ollow-up was used o classi y pa ien s a baseline.
Subsequen ly, obesi y (BMI 30 kg/m
2
) and inc eased HbA
1c
le el (>75 mmol/mol) we e de e mined based on he mos
ecen measu emen a he s a o each in e al. We used
s epwise model building o adjus men o po en ial con-
ounde s. In Model 1, we adjus ed o all po en ial con ound-
e s, while in Model 2 we pe o med addi ional adjus men o
numbe o yea s o pas exposu e o non-gla gine insulins
be o e he s a o gla gine as a con inuous a iable, o adjus
o he po en ial e ec o pas exposu e o non-gla gine
insulins on he associa ion be ween gla gine use and b eas
cance isk among swi che s. We e alua ed he linea i y
assump ion by adding a squa ed e m o he model, oge he
wi h he con inuous a iable.
S a is ical analysis
Mul i a ia e Cox p opo ional haza ds models we e used o
es ima e he haza d a io (HR) and 95% con idence in e als
(CI) o b eas cance associa ed wi h he use o gla gine, wi h
su i al ime in 30-day in e als as he ime a iable. Fo all
models, ‘ne e use’ o gla gine was used as he e e ence ca -
ego y. In addi ion o he analyses s a i ied by ca ego ies o
cumula i e du a ion o use, we pe o med p- end analyses,
whe e cumula i e exposu e o insulins was included as a con-
inuous a iable.
In a sensi i i y analysis, an ex ended ca ego y o cumula-
i e du a ion o gla gine exposu e was added – ‘0–1 yea s’,
‘1–3 yea s’, o ‘3–5 yea s’, and ‘>5 yea s’ – when s udy powe
Figu e 1. Schema ic ep esen a ion o exposu e measu es used. The basic ime-dependen design conside s a pa ien exposed om he i s p esc ip ion o gla gine
onwa d. Cumula i e exposu e measu es we e included as a e inemen , whe e pa ien s a e s a i ied by (a) cumula i e exposu e o insulin gla gine du ing ollow-up,
(b) du a ion o exposu e o o he insulin ypes be o e he s a o gla gine ea men , and (c) s a i ied o insulin-na
€
ı e s a e s o gla gine and pa ien s swi ched o
gla gine.
ACTA ONCOLOGICA 853
was su icien . In a sepa a e analysis, he cumula i e du a ion-
esponse e ec was s udied among gla gine use s independ-
en ly. He e, pa ien s s a ed on gla gine we e censo ed a he
ime a di e en insulin ype was p esc ibed. In his sensi i i y
analysis, he lowes ca ego y o cumula i e exposu e was
aken as he e e ence.
All da a managemen and s a is ical analyses (PROC
PHREG) we e conduc ed using SAS 9.2 (SAS Ins i u e Inc, Ca y,
NC, USA).
Resul s
Fo his s udy, we selec ed 12 468 emale inciden insulin
use s o ou inal s udy coho (Supplemen al Figu e A, a ail-
able online a h p://www.in o maheal hca e.com). Baseline
cha ac e is ics o new use s o insulin who ecei ed a i s
p esc ip ion o gla gine (n¼3858) o non-gla gine insulins
(n¼8610) a e shown in Table 1. The median du a ion o
ollow-up was compa able be ween he gla gine and non-
gla gine s a e s (5.0 s. 5.1 yea s), as was he median du -
a ion o insulin exposu e du ing ollow-up; 2.6 yea s o
gla gine use among gla gine s a e s, and 3.0 yea s o non-
gla gine insulin use among non-gla gine s a e s. Gla gine
s a e s we e in gene al olde a baseline (median age o 66
s. 61 yea s). O he non-gla gine s a e s, he majo i y
ecei ed a i s p esc ip ion o insulin aspa (44.6%) o
human insulin (39.4%). Gla gine s a e s in gene al ecei ed
NIADs in he yea p io o baseline (95.3%).
Risk o b eas cance
Du ing a o al ollow-up o 66 151 pe son yea s, 186 b eas
cance cases occu ed. O hese, 76 occu ed in pa ien s
a e exposu e o gla gine (3.0 pe 1000 pe son yea s), and
110 in pa ien s ne e exposed o gla gine (2.7 pe 1000
pe son yea s). In ou model adjus ed o po en ial con-
ounde s (Model 1), no disce nible inc ease in b eas cance
isk was associa ed wi h ‘e e use’ o gla gine (HR 1.06, 95%
CI 0.79–1.44), as compa ed o ‘ne e use’ (Table 2). When
adjus ed o yea s o exposu e o o he insulins be o e he
s a o gla gine ea men (Model 2), no isk di e ence was
obse ed (HR 0.98, 95% CI 0.72–1.35).
Cumula i e exposu e measu es
S a i ica ion by cumula i e du a ion o exposu e o gla gine
du ing ollow-up (Figu e 1a,Table 2) did no show an associ-
a ion wi h b eas cance isk (p- end ¼0.83 in Model 1). E en
when cumula i e gla gine use o o e i e yea s was modeled
as a sepa a e ca ego y (sensi i i y analysis), no signi ican di -
e ence in isk was obse ed (HR 1.26, 95% CI 0.64–2.47 in
Model 1).
Among swi che s, s a i ica ion by p io exposu e o non-
gla gine insulins a he s a o gla gine ea men (Figu e 1b,
Table 2) showed a linea end wi h inc easing yea s o p io
exposu e o non-gla gine insulins (p- end ¼0.02 in Model 1).
He e, a signi ican h ee- old inc ease in b eas cance isk
was obse ed in swi che s wi h a his o y o non-gla gine
insulin use o mo e han h ee yea s, as compa ed o women
ne e exposed o gla gine (HR 3.17, 95% CI 1.28–7.84).
Among insulin-na€
ı e women (Figu e 1c,Table 3), no
inc eased b eas cance isk was associa ed wi h ‘e e use’ o
gla gine (HR 0.99, 95% CI 0.71–1.37). Also, no end wi h
cumula i e du a ion o gla gine exposu e was obse ed
(p- end ¼0.91, HR ¼0.99, 95% CI 0.90–1.10 pe addi ional yea
o exposu e). A e addi ional s a i ica ion (sensi i i y analysis),
no inc eased b eas cance isk was associa ed wi h 5 yea s
o cumula i e exposu e (HR ¼1.06, 95% CI 0.48–2.33).
Among swi che s, a sligh , non-signi ican ly inc eased
b eas cance isk was associa ed wi h ‘e e use’ o gla gine
Table 1. Baseline cha ac e is ics o inciden insulin use s s a ed on insulin gla -
gine, non-gla gine insulin, o bo h.
Gla gine coho Non-gla gine coho
(n¼3858) (n¼8610)
Follow-up (median, IQR) 5.0 (3.0–7.5) 5.1 (3.1–7.9)
Maximum 11.0 11.2
Age (median, IQR) 66 (55–76) 61 (45–72)
<30 43 (1.1) 165 (1.9)
30–40 183 (4.7) 1387 (16.1)
40–50 381 (9.9) 1025 (11.9)
50–60 736 (19.1) 1476 (17.1)
60–70 923 (23.9) 1894 (22.0)
70–80 937 (24.3) 1791 (20.8)
>80 655 (17.0) 872 (10.1)
BMI (median, IQR) 30.4 (26.0–35.3) 30.4 (25.9–35.4)
<20 125 (3.2) 337 (3.9)
20–25 589 (15.3) 1326 (15.4)
25–30 1085 (28.1) 2137 (24.8)
30–35 962 (24.9) 2054 (23.9)
>35 962 (24.9) 2086 (24.2)
Missing 135 (3.5) 670 (7.8)
HbA
1c
(median, IQR) 79.1 (67.1–95.5) 78.0 (63.8–94.4)
<32 mmol/mol 8 (0.2) 39 (0.5)
32–64 mmol/mol 689 (17.9) 1756 (20.4)
64–75 mmol/mol 815 (21.1) 1250 (14.5)
>75 mmol/mol 2104 (54.5) 3796 (44.1)
Missing 242 (6.3) 1769 (20.5)
Smoking habi
Non-smoke 1900 (49.2) 4187 (48.6)
Cu en smoke 550 (14.3) 1398 (16.2)
Ex-smoke 983 (25.5) 2051 (23.8)
Missing 425 (11.0) 974 (11.3)
Medical diagnosis (e e be o e)
O he cance 255 (6.6) 583 (6.8)
Oopho ec omy 6 (0.2) 25 (0.3)
Type o insulin (a baseline)
Gla gine 3858 (100.0) 0 (0.0)
Non-gla gine 2888 (7.5) 8610 (100.0)
Human insulin 12 (0.3) 3394 (39.4)
Aspa 207 (5.4) 3841 (44.6)
De emi 1 (0.0) 1186 (13.8)
Glulisine 32 (0.8) 16 (0.2)
Lisp o 38 (1.0) 656 (7.6)
O he insulins 0 (0.0) 27 (0.3)
Medica ion use (yea p io o index)
NIADs
None 220 (5.7) 2093 (24.3)
Me o min 3014 (78.1) 5233 (60.8)
Sul onylu eas 3158 (81.9) 5174 (60.1)
Thiazolidinediones 1331 (34.5) 2101 (24.4)
O he * 518 (13.4) 826 (9.6)
HRT 286 (7.4) 594 (6.9)
S a ins 2701 (70.0) 4722 (54.8)
BMI: body mass index; HbA
1c
: glyca ed hemoglobin; HRT: ho mone eplacemen
he apy; IQR: in e qua ile ange; NIAD: non-insulin an idiabe ic d ug.
*Glinides, alpha-glucosidase inhibi o s, glucogon-like pep ide 1 agonis s, dipep-
idyl pep idase-4 inhibi o s, gua gum.
854 P. J. H. L. PEETERS ET AL.
(HR ¼1.40, 95% CI 0.83–2.34). Mo eo e , a non-signi ican
end was obse ed wi h cumula i e numbe o yea s o gla -
gine exposu e (p- end ¼0.24, HR ¼1.10, 95% CI 0.94–1.29
pe addi ional yea o exposu e in Model 1). Adjus men o
numbe o yea s o exposu e o non-gla gine insulins be o e
he s a o gla gine ea men (Model 2) esul ed in no ice-
able educ ions in isk es ima es. The HR o ‘e e use’ o gla -
gine in swi che s was educed o 0.97 (95% CI 0.47–1.99),
while he HR o he highes ca ego y o cumula i e gla gine
exposu e was educed om 1.58 (95% CI 0.63–3.94) o 1.14
(95% CI 0.42–3.09) (Table 3). In addi ion, he non-signi ican
end wi h cumula i e numbe o yea s o gla gine exposu e
disappea ed a e adjus men o cumula i e numbe o yea s
o exposu e o non-gla gine insulins (p- end ¼0.99,
HR ¼1.00, 95% CI 0.91–1.10 pe addi ional yea o exposu e,
Model 2 (no shown)). In his model, a signi ican end was
obse ed wi h numbe o yea s o p io non-gla gine insulin
exposu e (p- end ¼0.02, HR ¼1.24, 95% CI 1.03–1.50 pe
addi ional yea o exposu e, Model 2) (no shown).
Resul s om ou sensi i i y analysis ha censo ed gla gine
insulin use s i any o he ype o insulin was ini ia ed, also
showed no end wi h cumula i e du a ion o use (Supplemen al
Table A).
Discussion
In his coho s udy among women wi h ype 2 diabe es
newly s a ed on insulin, gla gine use was no associa ed wi h
an inc eased isk o b eas cance a e a median ollow-up o
Table 2. Haza d a ios o b eas cance associa ed wi h he use o insulin gla gine, s a i ied by cumula i e du a ion o gla gine use du ing ollow-up and by
cumula i e exposu e o o he insulins be o e he ini ia ion o gla gine he apy.
E en s Pe son yea s IR Age adj. HR (95% CI) Model 1 HR (95% CI)* Model 2 HR (95% CI)
†
Use o non-gla gine insulins‡110 40912.6 2.7 1 Re e ence 1 Re e ence 1 Re e ence
E e use o gla gine 76 25238.5 3.0 1.08 0.81–1.45 1.06 0.79–1.44 0.98 0.72–1.35
Cumula i e gla gine use§,k
<1 yea 29 8621.0 3.4 1.11 0.74–1.68 1.15 0.76–1.76 1.05 0.68–1.62
1–3 yea s 26 8994.3 2.9 1.02 0.66–1.56 0.99 0.64–1.53 0.91 0.58–1.42
>3 yea s 21 7623.1 2.8 1.12 0.69–1.81 1.05 0.64–1.70 0.99 0.61–1.62
3–5 yea s 11 4550.0 2.4 0.97 0.52–1.81 0.91 0.48–1.71 0.86 0.45–1.61
>5 yea s 10 3073.1 3.3 1.37 0.70–2.67 1.26 0.64–2.47 1.22 0.62–2.39
Cumula i e p io non-gla gine use¶,#
None 59 19923.3 3.0 1.03 0.75–1.41 0.99 0.71–1.37
0–3 yea s 12 4628.8 2.6 1.08 0.59–1.96 1.14 0.62–2.07
>3 yea s** 5 686.4 7.3 3.11 1.26–7.67 3.17 1.28–7.84
adj: adjus ed; CI: con idence in e al; HR: haza d a io; IR: incidence a e in e en s/1000 pe son yea s.
*Model 1, adjus ed o po en ial con ounde s; i.e. obesi y, smoking, alcohol use, HbA
1c
>75 mmol/mol, his o y o oopho ec omy o o he cance ypes, and use o
me o min, sul onylu eas, gli azones, ho mone eplacemen he apy, o s a ins;
†Model 2, addi ional adjus men o numbe o yea s o exposu e o o he non-gla gine insulin(s) a he s a o gla gine ea men as a con inuous a iable;
‡Pe son- ime wi hou any his o y o insulin gla gine use;
§Cumula i e numbe o yea s o cu en exposu e o insulin gla gine du ing ollow-up;
¶Cumula i e numbe o yea s o cu en exposu e o non-gla gine insulins be o e he s a o gla gine ea men ;
**Median pas exposu e 4.4 (in e qua ile ange, 3.6–5.6 yea s; maximum, 10.3 yea s).
Linea ends based on he slope o con inuous cumula i e numbe o yea s o cu en exposu e in Model 1:
kp- end ¼0.83, (HR ¼1.01, 95% CI 0.92–1.10), o cumula i e cu en exposu e o gla gine;
#p- end ¼0.02, (HR ¼1.24, 95% CI 1.03–1.49), o cumula i e cu en exposu e o non-gla gine insulin(s).
Table 3. Haza d a ios o b eas cance associa ed wi h he use o insulin gla gine, among insulin-na
€
ı e gla gine use s and gla gine use s wi h p io exposu e o
o he insulins, s a i ied by ca ego ies o cumula i e gla gine use and adjus ed o use o o he insulins be o e he s a o gla gine.
E en s Pe son yea s IR Age adj. HR (95% CI) Model 1 HR (95% CI)* Model 2 HR (95% CI)†
Use o non-gla gine insulin‡110 40912.6 2.7 1 Re e ence 1 Re e ence 1 Re e ence
E e use o gla gine 76 25238.5 3.0 1.08 0.81–1.45 1.06 0.79–1.44 0.98 0.72–1.35
Insulin-na
€
ı e gla gine use s§59 19923.3 3.0 1.02 0.74–1.41 0.99 0.71–1.37
Cumula i e gla gine usek
<1 yea 23 6759.8 3.4 1.09 0.69–1.71 1.11 0.69–1.77
1–3 yea s 20 7119.9 2.8 0.96 0.59–1.54 0.91 0.56–1.49
>3 yea s 16 6043.6 2.6 1.05 0.61–1.80 0.96 0.56–1.66
3–5 yea s 9 3610.5 2.5 0.97 0.49–1.93 0.90 0.45–1.80
>5 yea s 7 2433.0 2.9 1.18 0.54–2.57 1.06 0.48–2.33
Pa ien s swi ched o gla gine¶17 5315.2 3.2 1.33 0.80–2.22 1.40 0.83–2.34 0.97 0.47–1.99
Cumula i e gla gine use#
<1 yea 6 1861.2 3.2 1.24 0.55–2.83 1.32 0.58–3.03 0.84 0.31–2.31
1–3 yea s 6 1874.4 3.2 1.31 0.57–2.98 1.36 0.59–3.10 0.89 0.33–2.37
>3 yea s 5 1579.6 3.2 1.59 0.64–3.95 1.58 0.63–3.94 1.14 0.42–3.09
adj: adjus ed; CI: con idence in e al; HR: haza d a io; IR: incidence a e in e en s/1000 pe son yea s.
*Model 1, adjus ed o po en ial con ounde s; i.e. obesi y, smoking, alcohol use, HbA
1c
>75 mmol/mol, his o y o oopho ec omy o o he cance ypes, and use o
me o min, sul onylu eas, gli azones, ho mone eplacemen he apy, o s a ins;
†Model 2, addi ional adjus men o numbe o yea s o exposu e o o he non-gla gine insulin(s) a he s a o gla gine ea men as a con inuous a iable;
‡Pe son- ime wi hou any his o y o insulin gla gine use;
§Pa ien s wi hou pas cumula i e exposu e o o he insulins a he s a o gla gine he apy;
¶Pa ien s wi h pas cumula i e exposu e o o he insulins a he s a o gla gine he apy.
Linea ends based on he slope o con inuous cumula i e numbe o yea s o cu en exposu e in Model 1:
kp- end ¼0.91, (HR ¼0.99, 95% CI 0.90–1.10), o cumula i e yea s exposed o gla gine;
#p- end ¼0.24, (HR ¼1.10, 95% CI 0.94–1.29), o cumula i e yea s exposed o gla gine.
ACTA ONCOLOGICA 855

i e yea s as compa ed o use o o he insulins. Howe e , a
di e ence in b eas cance isk be ween insulin-na€
ı e new
use s o gla gine and women who swi ched o gla gine a e
ha ing used o he ypes o insulin was obse ed. Mo e speci -
ically, no associa ion be ween gla gine use (ei he in gene al
o wi h cumula i e use) and b eas cance isk was seen
among insulin-na€
ı e new use s o gla gine, e en a e i e
cumula i e yea s o gla gine exposu e. In con as , a non-sig-
ni ican inc ease in b eas cance isk was ound among
pa ien s who swi ched o gla gine, depending on he numbe
o yea s o pas insulin use. Tha is, a signi ican end was
obse ed o each addi ional yea o non-gla gine exposu e
be o e he s a o gla gine ea men .
Ou esul s ega ding insulin-na€
ı e pa ien s (i.e. wi hou
p io exposu e o o he insulins) a e in ag eemen wi h hose
om mos obse a ional s udies ha used cumula i e expos-
u e measu es. In he p e ious s udies, ou ou o i e did no
show an associa ion be ween cumula i e du a ion o gla gine
use and b eas cance isk among insulin-na€
ı e s a e s o
gla gine [13,15–17]. The s udy by Habel e al. (2013) did
epo an inc eased b eas cance isk associa ed wi h
ex ended du a ion (2 yea s) o use (HR ¼1.6, 95% CI
1.0–2.8) [14]. This esul migh be a chance inding, as wi h a
median du a ion o gla gine use o 1.2 yea s hey we e
unable o assess pa e ns o isk wi h longe du a ion o use.
In ac , all p e ious s udies among insulin-na€
ı e gla gine use s
we e limi ed by insu icien s udy powe o obus ly es ima e
e ec s o long-s anding (>3 yea s) gla gine exposu e.
Mo eo e , ou esul s a e also in line wi h hose om clinical
ials among new use s o insulin ha consis en ly showed no
inc eased cance isk associa ed wi h gla gine exposu e
[21–23]. The ORIGIN ial, wi h a median ollow-up o 6.2
yea s, ound no inc eased isk o b eas cance among
pa ien s assigned o gla gine e sus s anda d ca e. Howe e ,
wi h only 28 b eas cance cases in bo h ea men a ms,
s udy powe was limi ed [22].
Among pa ien s swi ched o gla gine a e ha ing used
o he insulins, we obse ed a non-signi ican inc ease in isk
associa ed wi h gla gine use. This esul is in line wi h ha
o Suissa e al. (2011) who epo ed a signi ican isk inc ease
associa ed wi h gla gine use a e i e yea s o mo e among
swi che s [13]. Howe e , he 2.7- old isk inc ease (95% CI
1.1–6.5) ound in hei s udy is much la ge han he one
obse ed in ou s udy. Con e sely, he only o he s udy ha
included swi che s, ound no inc eased isk associa ed wi h
du a ion o gla gine use, bu was limi ed by a ela i ely sho
ollow-up o gla gine use s (median o 2.3 yea s) [14]. In ou
s udy, we obse ed ha b eas cance isk inc eased wi h
each added yea o non-gla gine insulin use be o e he s a
o gla gine (i.e. e ec modi ica ion). Nei he o he p e ious
s udies assessed he e ec o pas insulin exposu e on he
associa ion be ween gla gine use and b eas cance isk.
Suissa e al. a e hus a he only ones o acknowledge ha
du a ion o insulin use be o e he s a o gla gine use
should be aken in o accoun . Howe e , by ma ching on du -
a ion o pas use, he amoun o a po en ial e ec was no
measu ed.
Ex ensi e pas use (3 yea s) o non-gla gine insulins was
associa ed wi h a h ee- old inc ease in b eas cance isk
among pa ien s swi ched o gla gine. Howe e , when consid-
e ing la ency pe iods and he longe du a ion o ype 2 dia-
be es and ea men he eo [24], i is impossible o a ibu e
his excess isk among swi che s o a single ac o (i.e. gla -
gine use). None heless, his esul sheds some ligh on he
dynamics linked o he appa en di e ence in b eas cance
isk seen in insulin-na€
ı e pa ien s s a ed on gla gine and
swi che s wi h pas exposu e o o he insulins. The impo -
ance o aken p io use o o he insulins in o accoun was
demons a ed by he no iceable educ ion in all isk es ima es
o b eas cance associa ed wi h gla gine use a e adjus -
men o he numbe o yea s p e iously exposed o o he
insulins.
Al e na i e explana ions o he di e ence in b eas cance
isk associa ed wi h gla gine use be ween insulin-na€
ı e s a -
e s o gla gine and swi che s may en ail ha o al du a ion o
insulin use (o diabe es du a ion), a he han exposu e o any
pa icula insulin ype, is associa ed wi h an inc eased isk o
b eas cance . In addi ion, pa ien s swi ched o gla gine may
di e om insulin-na€
ı e pa ien s s a ed on gla gine. I gla -
gine is used as an add-on in p e alen insulin use s wi h
poo ly con olled blood glucose le els, a possible a ia ion in
backg ound isk migh be in oduced. Such a dynamic could
lead o channeling and po en ial p o opa hic bias among
swi che s. This al e na i e hypo hesis migh be e alua ed in
u u e s udies.
Majo s eng hs o ou s udy include he use o ime-
dependen exposu e measu es based on p esc ip ion da a o
de e mine insulin exposu e. This de ini ion minimizes expos-
u e misclassi ica ion and mo e accu a ely e lec s eal expos-
u e han ime since he s a o ollow-up, as used in p e ious
s udies. In addi ion, as only inciden insulin use s (1 yea
wi hou any insulin use a baseline) we e included, we had
comp ehensi e in o ma ion on insulin use o pa ien s
included in he coho . In pa ien s who swi ched o gla gine
du ing ollow-up, we we e able o de e mine he e ec o
pas insulin use on he associa ion be ween gla gine use and
b eas cance isk. To ou knowledge, we a e he i s o
assess his e ec . Fu he mo e, we had h ee addi ional yea s
o ollow-up as compa ed o he s udy by Suissa e al. and
we e he eby able o de e mine b eas cance isk es ima es
o long-s anding gla gine use in insulin-na€
ı e pa ien s.
Se e al limi a ions o ou s udy should be no ed as well.
Fi s o all, he compa a o consis ed o all o he (non-
gla gine) insulins. This ca ego y included bo h sho - and
long-ac ing insulins, esul ing in a he e ogeneous e e ence
g oup. Howe e , i can be ega ded as a ele an e e ence
g oup when you wan o assess gla gine associa ed isks e -
sus he o he ea men op ions a ailable. Con e sely, his
app oach did no allow o di ec compa isons be ween long-
ac ing insulin ypes. Second, ou models did no accoun o
any addi ional e ec s o combined use o bo h gla gine and
non-gla gine insulins. Ideally, combined use should be con-
side ed as a sepa a e ca ego y. Also, we we e unable o
make di ec compa isons be ween gla gine and non-gla gine
insulin use s wi h he same du a ion o exposu e. Thi d, we
did no ake la ency in o accoun , as ollow-up ime was
insu icien o inco po a e a sensible la ency pe iod o b eas
cance . Fou h, as he coho was es ic ed o new use s o
856 P. J. H. L. PEETERS ET AL.
insulin a coho en y, s udy powe o analyze e ec s wi h
cumula i e du a ion o use was limi ed o he g oup o
swi che s, hinde ing u he s a i ica ion by s a a o cumula-
i e yea s o pas non-gla gine insulin use. Fi h, as CPRD co -
e s a dynamic pa ien popula ion (i.e. 7% o he o al UK
popula ion), pa ien s who ans e o a gene al p ac i ione
who does no p o ide da a o CPRD a e los o ollow-up.
Finally, when i ing se e al exposu e models on he same
da a, ocus should no be on indi idual signi ican esul s, bu
he o al o analyses should be seen in pe spec i e and in e -
p e ed oge he [25].
In conclusion, exposu e o insulin gla gine did no appea
o be associa ed wi h an inc eased b eas cance isk in insu-
lin-na€
ı e pa ien s. Ou esul s, howe e , do indica e an associ-
a ion be ween gla gine use and b eas cance among
pa ien s p e iously ea ed wi h o he insulins be o e he s a
o gla gine. Gla gine use in pa ien s wi h ex ensi e pas
exposu e o o he insulin ypes was associa ed wi h a h ee-
old inc eased isk. The e o e, obse a ional s udies need o
ake pas exposu e o o he insulins in o accoun when s udy-
ing b eas cance isk associa ed wi h gla gine use. Fu u e
s udies should conside whe he his excess isk o b eas can-
ce obse ed in pa ien s swi ched o gla gine is caused by
p o opa hic bias.
Disclosu e s a emen
The esea ch leading o he esul s o his s udy has ecei ed unding
om he Eu opean Communi y’s Se en h F amewo k P og am (FP-7)
unde g an ag eemen numbe 282526, he CARING p ojec . The unding
sou ce had no ole in s udy design, da a collec ion, da a analysis, da a
in e p e a ion o w i ing o he epo .
The Depa men o Pha macoepidemiology and Clinical Pha macology
employing au ho s Paul J. H. L. Pee e s, Ma oes T. Bazelie and F ank de
V ies ecei ed un es ic ed unding o pha macoepidemiological esea ch
om GlaxoSmi hKline, No o No disk, he p i a e–public- unded Top
Ins i u e Pha ma (h p://www. ipha ma.nl; includes co- unding om uni-
e si ies, go e nmen and indus y), he Du ch Medicines E alua ion
Boa d and he Du ch Minis y o Heal h.
Hube G. M. Leu kens is employed by U ech Uni e si y as p o esso
conduc ing esea ch unde he umb ella o he WHO Collabo a ing
Cen e o pha maceu ical policy and egula ion. This Cen e ecei es no
di ec unding o dona ions om p i a e pa ies, including pha ma indus-
y. Resea ch unding om public-p i a e pa ne ships, e.g. IMI, TI Pha ma
(www. ipha ma.nl) is accep ed unde he condi ion ha no company-
speci ic p oduc o company ela ed s udy is conduc ed. The Cen e has
ecei ed un es ic ed esea ch unding om public sou ces, e.g.
Ne he lands O ganiza ion o Heal h Resea ch and De elopmen
(ZonMW), he Du ch Heal h Ca e Insu ance Boa d (CVZ), EU 7 h
F amewo k P og am (FP7), Du ch Medicines E alua ion Boa d (MEB), and
Du ch Minis y o Heal h.
Anssi Au inen is employed by he Uni e si y o Tampe e as p o esso
and has no pe sonal o inancial con lic o in e es o epo .
Tjee d P. an S aa has pa icipa ed in expe mee ings wi h Glaxo
Smi h Kline and Boeh inge and has p o ided me hodological ad ice o
Lase (all un ela ed o he subjec o his manusc ip ).
Ma ie L. De B uin is employed by U ech Uni e si y as a senio
esea che conduc ing esea ch in collabo a ion wi h he WHO
Collabo a ing Cen e o pha maceu ical policy and egula ion. This
Cen e ecei es no di ec unding o dona ions om p i a e pa ies,
including he pha ma indus y. Resea ch unding om public-p i a e pa -
ne ships, e.g. IMI and TI Pha ma (h p://www. ipha ma.nl) is accep ed
unde he condi ion ha no company-speci ic p oduc o company
ela ed s udy is conduc ed. The Cen e has ecei ed un es ic ed esea ch
unding om public sou ces, e.g. Ne he lands O ganiza ion o Heal h
Resea ch and De elopmen (ZonMW), he Du ch Heal h Ca e Insu ance
Boa d (CVZ), EU 7 h F amewo k P og am (FP7), Du ch Medicines
E alua ion Boa d (MEB) and Du ch Minis y o Heal h.
None o he abo emen ioned unding sou ces had a ole in he
design, conduc , analysis, o epo ing o his s udy.
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