Toxicity and risk factors after combined high-dose-rate brachytherapy and external beam radiation therapy in men ≥75 years with localized prostate cancer

PURPOSE: Combined high-dose-rate brachytherapy (HDR-BT) and external beam radiation therapy (EBRT) is a favorable treatment option in non-metastatic prostate cancer. However, reports on toxicity and outcome have mainly focused on younger patients. We aimed to determine toxicity and biochemical control rates after combined HDR-BT and EBRT in men ≥75 years.

METHODS: From 1999 to 2015, 134 patients aged ≥75 years (median 76 years; 75-82 years) were identified. Patients received 18 Gy of HDR-BT (9 Gy/fraction on days 1 and 8) with an iridium-192 source. After 1 week, supplemental EBRT with a target dose of 50.4 Gy was started (delivered in 1.8 Gy fractions).

RESULTS: Median follow-up time was 25 months (0-127 months). No severe (grade 4) gastrointestinal (GIT) or genitourinary (GUT) toxicities were observed. In 76 patients (56.7%), 3D conformal radiation therapy (CRT) and in 34.3% intensity-modulated radiotherapy (IMRT) was applied. CRT-treated patients were at a 2.17-times higher risk (hazard ratio [HR]: 2.17, 95% confidence interval [CI]: 1.31-3.57, p = 0.002) of experiencing GUT. GIT risks could be reduced by 78% using IMRT (HR: 0.22, 95% CI: 0.07-0.75, p = 0.015). Patients with a higher T stage (T2c-3a/b) were less likely to experience GIT or GUT (HR: 0.49, 95% CI: 0.29-0.85, p = 0.011 and HR: 0.5, 95% CI: 0.3-0.81, p = 0.005, respectively).

CONCLUSION: HDR-BT/EBRT is a well-tolerated treatment option for elderly men ≥75 years with a limited number of comorbidities and localized intermediate- or high-risk prostate cancer. IMRT should be favored since side effects were significantly reduced in IMRT-treated patients.