Second primary cancer risk after breast,colorectal and prostate cancers: Results from long-term follow-up of cancer registry patients in Scotland


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A. Coyte1, D. Morrisson2,3
1University of Glasgow Medical School, Glasgow, UK, 2West of Scotland Cancer Surveillance Unit, Scotland, UK, 3University of Glasgow, Glasgow, UK

Background

Increasing survival from most of the common cancers has resulted in a longer period during which patients might develop second primary cancers (SPC). It is therefore increasingly important to quantify risks and sites of second primary cancers so that patients can be supported to take appropriate preventative measures.

Method

We used Scottish Cancer Registry data for all first primary cancers diagnosed between January 1997 and December 1998 for residents of the West of Scotland. Patients were followed up until date of SPC, death or censor (28 February 2011). Crude and European standardised incidence rates, Kaplan-Meier and Cox proportional hazards models were used to quantify risks of SPCs for breast, colorectal and prostate patients. IARC rules on SPC defining were adopted.

Results

29,232 patients were included. Patients with breast, prostate or colorectal cancer had higher incidences of SPCs than the general population. Index prostate cancer patients had the largest increase in SPC risk with a Standardised Incidence Ratio (SIR) of 4.8; SIRs for breast and colorectal patients were 2.2 and 3.7, respectively. Smoking related neoplasms accounted for around half of all SPCs (index breast 48%, colorectal 42%, prostate 51%) and colorectal cancers were the second commonest site of SPC. Multivariate hazard models showed older age was associated with increased incidence of second primaries in all index sites. In index colorectal cancer patients, males were at increased risk (age, Dukes' adjusted female HR=0.61, 95% CI 0.48-0.77).

Conclusion

Patients with prostate, breast and colorectal cancers are at increased risk of second primary cancers, which are mainly smoking-related and colorectal cancers. Support for smoking cessation and improvement of modifiable risk factors for colorectal cancer may be appropriate for patients who have survived their index cancer.