Purpose: We conducted an exploratory study of brain tumors that occurred as a second primary malignancy to identify potential risk factors for brain tumors.
Methods: Using data from the Surveillance, Epidemiology, and End Results (SEER) Program, we calculated the sex-specific standardized incidence ratio (SIR), adjusted to age and time period, as an estimate of the relative risk (RR) of developing a second primary brain tumor following other cancers.
Results: We found an elevated RR of brain tumors after bladder cancer in both men (RR, 1.7; 95% confidence interval [CI], 1.2 to 2.3) and women (RR, 1.7; 95% CI, 0.8 to 3.2); this effect was present for both astrocytoma and glioblastoma multiforme. Elevated RRs of brain tumors were also found after sarcoma (RR, 4.4; 95% CI, 1.8 to 9.0) and leukemia (RR, 2.9; 95% CI, 1.6 to 4.8) in men, and after colorectal cancer (RR, 1.8; 95% CI, 1.3 to 2.4) and endometrial cancer (RR, 1.4; 95% CI, 1.0 to 1.9) in women. The highest RR observed in this study was for CNS lymphoma following any first primary malignancy in men (RR, 7.9; 95% CI, 5.5 to 11.0).
Conclusion: The associations of brain tumors with bladder, colorectal, and endometrial cancers in women, and an increased occurrence of CNS lymphoma as a second malignancy in men, are new findings that have not been described previously.