2631 - Risk of Secondary Malignancy after Radiotherapy for Benign Intracranial Tumors
Presenter(s)
H. S. Mahmood1, J. B. Yu2, D. P. Horowitz3, L. A. Kachnic3, S. K. Cheng4, T. J. C. Wang5, and C. J. Kinslow3; 1Columbia University Medical Center, New York, NY, 2Department of Radiation Oncology and Applied Sciences, Dartmouth Geisel School of Medicine, Lebanon, NH, 3Department of Radiation Oncology, Columbia University Irving Medical Center, New York, NY, 4Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, 5Columbia University, New York, NY
Purpose/Objective(s): Patients undergoing definitive management of benign brain tumors should be counseled on the risk of secondary malignancy when radiotherapy (RT) is being considered. However, there are few data available to guide physicians when counseling patients. Our aim was to further elucidate the risk of secondary malignancy for patients after undergoing radiation therapy to the brain for the treatment of benign intracranial tumors.
Materials/Methods: This cohort study included patients newly diagnosed with benign intracranial tumors between 2000-2020 and were managed with surgery or radiotherapy in the Surveillance, Epidemiology, and End Results (SEER) Program Database. We calculated standardized incidence ratios (SIR) and absolute excess risks of secondary benign or malignant brain tumors using a latency of exclusion period of 2 years after diagnosis.
Results: We identified 180,927 patients diagnosed with benign brain tumors between 2000 and 2020, with a total follow-up of 1,069,088 person-years (mean 5.9 years). The SIR for any new brain tumor (benign or malignant) was highest in the first-year after diagnosis (SIR 36.91 [95% CI, 35.56-38.29]) [Excess Risk: 169.37 additional cases per 10,000 person years] and declined over time (SIR 4.58 [95% CI, 4.09-5.12] [Excess Risk: 17.26 additional cases per 10,000 person years] in the second year, and 2.44 [95% CI, 2.07-2.85] [Excess Risk: 8.19 additional cases per 10,000 person years] after 10 years). Including only patients with benign brain tumors with >2 years of follow-up and a latency of exclusion of 2 years (133,279 patients), the SIR for any brain tumor or any malignant brain tumor was 2.92 (95% CI, 2.76-3.10) [Excess Risk: 9.55 additional cases per 10,000 person years] and 3.30 (95% CI, 2.95-3.67) [Excess Risk: 2.99 additional cases per 10,000 person years], respectively. For patients who received surgery and no radiotherapy, the SIR was 3.20 (95% CI, 2.92-3.50) [Excess Risk: 9.93 additional cases per 10,000 person years] and 4.02 (95% CI, 3.41-4.70), [Excess Risk: 3.57 additional cases per 10,000 person years] respectively. For patients who received radiotherapy, the SIR was 3.76 (95% CI, 3.20-4.40) [Excess Risk: 13.44 additional cases per 10,000 person years] and 4.64 (95% CI, 3.45-6.10), [Excess Risk: 4.69 additional cases per 10,000 person years] respectively.
Conclusion: Patients who receive radiotherapy for benign intracranial brain tumors have an elevated risk of secondary benign or malignant brain tumors, although the absolute risk is extremely low. The risk is similar for patients who receive radiotherapy or surgery alone.