Kenny Chin, BS of the Icahn School of Medicine at Mount Sinai speaks about the ASTRO 2020 abstract 4021 Clinical and Treatment Characteristics of Secondary Bladder Malignancies following Low Dose Rate Brachytherapy for Prostate Cancer.
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Purpose/Objective(s): For patients with localized prostate cancer, brachytherapy is an effective choice. Although secondary malignancies are a well-known late complication of radiation therapy, there is minimal evidence from previous prostate brachytherapy on such malignancies. We tried to describe the clinical course and prognosis of prostate brachytherapy-associated secondary bladder malignancies.
Materials/Methods: For patients diagnosed with bladder cancer (1/2005-4/2019) who had previously undergone low dose rate (LDR) prostate brachytherapy, we queried our institutional database. It included patients with both muscle-invasive (T2+) and non-muscle-invasive (Tis-T1) bladder tumors; it excluded patients who were treated elsewhere or who were not assessable for lack of documentation. The clinical and disease-specific characteristics of the chart analysis were manually abstracted. Using Kaplan-Meier figures, survival outcomes were calculated.
Results: 27,462 patients with a history of prostate cancer were identified, of which 375 had a combined diagnosis of bladder cancer and 51 met the inclusion criteria. The median time from brachytherapy to the diagnosis of bladder cancer was 9.3 years (range 2.7-24 years); the median period of follow-up was 35.5 months. No patient had an unresectable (T4b) or metastatic (M1) disorder at the time of diagnosis. The posterior (34 percent) and lateral (60 percent) tumors were more common than the anterior (2 percent) bladder walls. 32 (63 percent) patients had the non-muscle invasive disease (NMIBC) and were treated with TURBT with intravesical induction/maintenance (n=16, 31 percent) or without (n=15, 29 percent). 19 (37%) patients had the muscle-invasive disease (MIBC); 2 of these patients were treated with serial TURBT, 11 with cystectomy, 5 with systemic chemotherapy, and 1 with definitive chemoradiation treatment. The 5-year progression-free survival rate for NMIBC and MIBC was 44.7% (95% CI 23.1-64.3) and 48.1% (95% CI 25.7-69.9) respectively; the 5-year survival rate for NMIBC and MIBC was 75.6% (95% CI 49.7-89.4) and 93.3% (95% CI 61.3-100) respectively. Just 2 of the 7 patient deaths recorded during follow-up were due to cancer of the bladder.