Table 7.
Factors associated with the cumulative incidence of a second cancer in Canadians (excluding Quebec) diagnosed with a first cancer in childhood or adolescence by selected types of first cancer, 1992–2014.
| Events | Crude SHR (95% CI) | p-value | Adjusted SHR (95% CI) | p-value | |
|---|---|---|---|---|---|
| All (N = 22,635; E = 395) | |||||
| Sex | 0•0003 | 0•0001 | |||
| male | 175 | —a | — | ||
| female | 220 | 1•445 (1•186–1•763) | 1•481 (1•213–1•811) | ||
| Diagnostic group of first cancerb | <0•0001 | <0•0001 | |||
| leukaemia | 60 | — | — | ||
| lymphoma | 85 | 2•261 (1•637–3•141) | <0•0001 | 2•294 (1•661–3•188) | <0•0001 |
| CNS | 50 | 1•314 (0•906–1•898) | 0•1464 | 1•309 (0•902–1•890) | 0•1521 |
| peripheral nervous cell | 30 | 2•829 (1•816–4•316) | <0•0001 | 2•730 (1•752–4•168) | <0•0001 |
| retinoblastoma | 5 | 1•715 (0•714–3•493) | 0•1748 | 1•722 (0•717–3•507) | 0•1721 |
| renal | 10 | 1•198 (0•615–2•141) | 0•5673 | 1•188 (0•610–2•124) | 0•5855 |
| hepatic | *c | ||||
| bone | 35 | 2•879 (1•900–4•301) | <0•0001 | 2•840 (1•873–4•245) | <0•0001 |
| soft tissue | 50 | 3•153 (2•149–4•597) | <0•0001 | 3•051 (2•076–4•454) | <0•0001 |
| germ cell | 20 | 1•313 (0•774–2•133) | 0•2895 | 1•349 (0•794–2•192) | 0•2457 |
| carcinomas | 30 | 1•440 (0•924–2•197) | 0•0974 | 1•309 (0•839–2•000) | 0•2208 |
| other/NEC | 5 | 1•502 (0•525–3•381) | 0•3836 | 1•374 (0•480–3•094) | 0•4932 |
| Calendar period of diagnosis | <0•0001 | <0•0001 | |||
| 1992–2004 | 275 | — | — | ||
| 2005–2014 | 120 | 2•178 (1•672–2•841) | 2•148 (1•648–2•804) | ||
| Synchronous first cancersd | <0•0001 | 0•0003 | |||
| no | 390 | — | |||
| yes | 5 | 6•472 (2•764–12•64) | 4•286 (1•818–8•429) | ||
| Leukaemia (N = 5965; E = 60) | |||||
| Calendar period of diagnosis | 0•0014 | 0•0015 | |||
| 1992–1994 | 25 | — | — | ||
| 1995–1999 | 10 | 0•409 (0•193–0•836) | 0•0156 | 0•410 (0•193–0•837) | 0•0157 |
| 2000–2004 | 10 | 0•707 (0•318–1•544) | 0•4213 | 0•696 (0•312–1•519) | 0•3984 |
| 2005–2009 | 10 | 1•248 (0•461–3•230) | 0•6559 | 1•243 (0•459–3•217) | 0•6617 |
| 2010–2014 | 5 | 3•391 (1•027–11•363) | 0•0291 | 3•375 (1•022–11•308) | 0•0298 |
| Age at diagnosis | 60 | 1•054 (1•010–1•098) | 0•0094 | 0•9436 | |
| Age at diagnosis*Time | 0•0971 | ||||
| Age at diagnosis over time (SHR per 1 year increase in age) | |||||
| At 0 years of follow-up | 0•997 (0•918–1•077) | ||||
| 1 year | 1•003 (0•929–1•077) | ||||
| 5 years | 1•027 (0•972–1•081) | ||||
| 10 years | 1•057 (1•013–1•103) | ||||
| 15 years | 1•089 (1•028–1•154) | ||||
| 20 years | 1•122 (1•030–1•223) | ||||
| Lymphoma (N = 3805; E = 85) | |||||
| Calendar period of diagnosis | 0•0025 | 0•0025 | |||
| 1992–1994 | 25 | — | — | ||
| 1995–1999 | 30 | 1•854 (0•991–3•656) | 0•0506 | 1•854 (0•991–3•656) | 0•0506 |
| 2000–2004 | 15 | 1•774 (0•774–4•134) | 0•1357 | 1•774 (0•774–4•134) | 0•1357 |
| 2005–2009 | 10 | 3•032 (1•093–8•353) | 0•0165 | 3•032 (1•093–8•353) | 0•0165 |
| 2010–2014 | 10 | 7•666 (2•559–23•839) | <0•0001 | 7•666 (2•559–23•839) | <0•0001 |
| CNS (N = 3670; E = 50) | |||||
| Calendar period of diagnosis | 0•0027 | 0•0027 | |||
| 1992–2004 | 30 | — | — | ||
| 2005–2014 | 20 | 3•112 (1•518–6•564) | 3•112 (1•518–6•564) | ||
| Peripheral nervous cell (N = 1060; E = 30) | |||||
| Calendar period of diagnosis | 0•0009 | 0•0012 | |||
| 1992–2004 | 15 | — | — | ||
| 2005–2014 | 15 | 3•736 (1•620–9•412) | 3•640 (1•575–9•188) | ||
| Synchronous first cancers | 0•0002 | 0•0004 | |||
| no | 30 | — | — | ||
| yes | * | ||||
| Carcinomas (N = 2195; E = 30) | |||||
| Sex | 0•0387 | 0•0301 | |||
| male | 5 | — | — | ||
| female | 25 | 2•746 (1•147–8•119) | 2•911 (1•213–8•622) | ||
| Age at diagnosis | 0•0171 | 0•0094 | |||
| 0–9 | 5 | — | — | ||
| 10–19 | 25 | 0•341 (0•149–0•918) | 0•312 (0•136–0•841) | ||
Note. Models are presented when an adequate number of second cancers (i.e. events) occurred and at least one explanatory variable was identified by the forward selection modelling procedure (alpha to enter = 0.05). For confidentiality, counts are randomly rounded using an unbiased random rounding scheme with a base of five. Counts may not sum to total due to random rounding. CI=confidence interval; CNS=central nervous system; E=number of people diagnosed with a second cancer; N=number of people included in the model; NEC=not elsewhere classified; SHR=subdistribution hazard ratio.
Reference group.
Defined according to the International Classification of Childhood Cancer (see Table 1). Unclassified cases were combined with the other category.
Fewer than five second cancers.
Synchronous first cancers are defined as more than one cancer diagnosed during the 60 day synchronous period.