The relative risk of second primary cancers in Austria's western states: a retrospective cohort study

Cancer survivors are at risk of developing a second primary cancer (SPC) later in life because of persisting effects of genetic and behavioural risk factors, the long-term sequelae of chemotherapy, radiotherapy and the passage of time. This is the first study with Austrian data on an array of entities, estimating the risk of SPCs in a population-based study by calculating standardized incidence ratios (SIRs).

This retrospective cohort study included all invasive incident cancer cases diagnosed within the years 1988 to 2005 being registered in the Tyrol and Vorarlberg Cancer Registries. Person years at risk (PYAR) were calculated from time of first diagnosis plus 2 months until the exit date, defined as the date of diagnosis of the SPC, date of death, or end of 2010, whichever came first. SIR for specific SPCs was calculated based on the risk of these patients for this specific cancer.

A total of 59,638 patients were diagnosed with cancer between 1988 and 2005 and 4949 SPCs were observed in 399,535 person-years of follow-up (median 5.7 years). Overall, neither males (SIR 0.90; 95% CI 0.86-0.93) nor females (SIR 1.00; 95% CI 0.96-1.05) had a significantly increased SIR of developing a SPC. The SIR for SPC decreased with age showing a SIR of 1.24 (95% CI 1.12-1.35) in the age group of 15-49 and a SIR of 0.85 (95% CI 0.82-0.89) in the age group of ≥ 65. If the site of the first primary cancer was head/neck/larynx cancer in males and females (SIR 1.88, 95% CI 1.67-2.11 and 1.74, 95% CI 1.30-2.28), cervix cancer in females (SIR 1.40, 95% CI 1.14-1.70), bladder cancer in males (SIR 1.20, 95% CI 1.07-1.34), kidney cancer in males and females (SIR 1.22, 95% 1.04-1.42 and 1.29, 95% CI 1.03-1.59), thyroid gland cancer in females (SIR 1.40, 95% CI 1.11-1.75), patients showed elevated SIR, developing a SPC.

Survivors of head & neck, bladder/kidney, thyroid cancer and younger patients show elevated SIRs, developing a SPC. This has possible implications for surveillance strategies.