A secondary bladder cancer (SBC) rarely occurs among patients with localized prostate cancer who have been treated with radiotherapy (RT), but the incidence rate is not insignificant, reports a study presented at EAU 2026. When it does appear, it usually becomes the primary cause of death in this population.
“Considering the potential impact on prostate cancer survivorship, this study highlights the importance of enhancing patient education and establishing appropriate surveillance guidelines to optimize outcomes,” said lead study author Dr Abdenour Nabid, CIUSSS de l'Estrie - CHUS, Department of Radiation Oncology, Sherbrooke, Canada.
Nabid and his team determined the incidence and related outcomes of SBC in a cohort of patients with localized prostate cancer treated with RT in two phase III trials.
Between October 2000 and September 2010, 630 patients with high-risk prostate cancer (HRPCa) who received androgen deprivation therapy (ADT) and RT and 600 with intermediate-risk prostate cancer (IRPCa) treated with RT with or without ADT were enrolled in two randomized controlled trials.
RT was delivered at a dose of 2 Gy daily for five times a week. Patients with HRPCa received 44 Gy in 4 1/2 weeks to the pelvis and 70 Gy in 7 weeks to the prostate, while those with IRPCa received 70 Gy (n=200) or 76 Gy (n=400) to the prostate alone.
Nabid and colleagues assessed outcomes until September 2025, comparing HRPCa and IRPCa using Fisher exact test or Mann-Whitney test for categorical or continuous variables, respectively. They also evaluated SBC between IRPCa and HRPCa using competing risks methods.
Of the 1,207 patients included in the analysis, 589 had IRPCa and 618 HRPCa. Twenty-three patients who did not receive RT were excluded. The median age at randomization was 71 years, with SBC occurring at a median age of 79 years. Age, comorbidities, and Zubrod performance scale were comparable between HRPCa and IRPCa patients, but not for clinical stage and Gleason score. [EAU 2026, abstract A0783]
Gradual occurrence
Thirty-six patients developed SBC over a median follow-up of 17.3 years, corresponding to a crude rate of 3.0 percent. No statistical difference was observed in SBC rates between patients who received treatment to the prostate alone and those who received RT to a larger field including the whole pelvis (2.5 percent vs 3.4 percent; p=0.38).
Thirty-five patients had available pathology, which revealed urothelial carcinoma in 30 individuals, including 16 invasive and 14 noninvasive types.
SBC did not occur rapidly after RT but rather slowly over a long period of time (1 to 18 years), at a median of 7.5 years. However, patients with HRPCa were more likely to develop SBC sooner than those with IRPCa (median 6.6 vs 8.6 years; p=0.03).
At 10 years, the rates of SBC were comparable between the IRPCa (1.4 percent, 95 percent confidence interval [CI], 0.7‒2.7) and HRPCa (2.5 percent, 95 percent CI, 1.5‒4.1) cohorts, with no significant difference in the global subdistribution hazard ratio (1.29, 95 percent CI, 0.67‒2.50; p=0.45).
Mortality rate among patients with SBC was high, with 29 (80.6 percent) deaths. Sixteen (55.2 percent) of these were caused by SBC, while three (10.3 percent) died from cardiovascular events and another three (10.3 percent) from prostate cancer, all in the HRPCa group.