Effect of prior radiation on stage, differentiation, and survival in bladder cancer

Abstract

Purpose: Clinically significant differences in radiation-related bladder tumors are not well-characterized, and survival analyses are needed. In this study, we aimed to utilize a national cancer database to evaluate the effect of prior radiation on tumor characteristics and survival in bladder cancer patients.

Methods: The Surveillance, Epidemiology, and End Results (SEER) 9 database was queried to identify patients diagnosed with bladder cancer as a second malignancy. Patients having undergone radiation prior to developing bladder cancer were selected for comparative analysis. Logistic regression was used to generate odds ratios to evaluate differences in differentiation, stage, grade, and tumor size. Kaplan-Meier analysis and Cox non-proportional hazards regression models were used to assess the association between previous radiation and bladder cancer survival.

Results: A total of 25,408 patients were identified, of which 14,570 patients had sufficient data for analysis. Of these, 5968 (41.0%) received radiation for their primary malignancy. Prior radiation conferred a lower risk of developing moderately- or poorly-differentiated bladder tumors and muscle invasive or node-positive disease. An increased risk of squamous cell carcinoma was noted (OR 1.43, CI 1.06-1.93). Prior radiation led to an increased risk of bladder cancer-specific (HR 1.13, CI 1.03-1.24) mortality at 5 years. The greatest effect of prior radiation was an increased risk of bladder cancer-specific mortality for carcinoma in situ at 5 years (OR 2.37, CI 1.45-3.86).

Conclusion: Prior radiation is associated with lower grade and stage of bladder tumors in addition to worse cancer-specific survival.

Keywords: Bladder cancer; Radiation-induced cancer; SEER program; Survival analysis; Tumor staging.