Second cancers in patients with brain tumours--impact of treatment.

The records of the Finnish Cancer Registry from 1953 to 1994 were used to assess the risk of subsequent primary cancer among 14,493 brain tumour patients. They had been treated with surgery only (n = 9804), radiotherapy (n = 4099), chemotherapy and radiotherapy (n = 493) or chemotherapy alone (n = 97). By the end of 1994, 403 subsequent primary cancers were registered in these patients, whilst the expected number based on national incidence was 332. The standardised incidence ratio (SIR) was 1.2 (95% confidence interval (CI) 1.1-1.3). A significant excess risk of tumours in the central nervous system (CNS) including meningeomas (SIR 2.6, 95% CI 1.7-3.8), non-Hodgkin's lymphoma (SIR 2.6, 95% CI 1.6-4.1) and skin melanoma (SIR 1.9, 95% CI 1.0-3.1) was observed. CNS tumours were observed in excess among patients treated with surgery alone (SIR 2.0, 95% CI 1.2-3.2) and with radiotherapy (SIR 5.1, 95% CI 2.5-9.4). In conclusion, brain tumours are associated with an increased risk of both CNS second tumours and non-CNS second cancers, especially non-Hodgkin's lymphoma and melanoma. A moderately increased risk of second tumours in the CNS was observed among brain tumour patients treated with surgery only and a larger excess among those treated with radiotherapy.