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

Abstract

Combined high-dose-rate brachytherapy (HDR-BT) and external beam radiation therapy (EBRT) is afavorable 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 ≥75years. From 1999 to 2015, 134 patients aged ≥75years (median 76years; 75-82years) were identified. Patients received 18 Gy of HDR-BT (9 Gy/fraction on days1 and8) with an iridium-192 source. After 1week, supplemental EBRT with atarget dose of 50.4 Gy was started (delivered in 1.8 Gy fractions). Median follow-up time was 25months (0-127months). No severe (grade4) gastrointestinal (GIT) or genitourinary (GUT) toxicities were observed. In 76patients (56.7%), 3D conformal radiation therapy (CRT) and in 34.3% intensity-modulated radiotherapy (IMRT) was applied. CRT-treated patients were at a2.17-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 ahigher Tstage (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). HDR-BT/EBRT is awell-tolerated treatment option for elderly men ≥75years with alimited 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.