Radiation dose escalation for localized prostate cancer: intensity-modulated radiotherapy versus permanent transperineal brachytherapy

Background: In the current study, the effects of dose escalation for localized prostate cancer treatment with intensity-modulated radiotherapy (IMRT) or permanent transperineal brachytherapy (BRT) in comparison with conventional dose 3-dimensional conformal radiotherapy (3D-CRT) were evaluated.

Methods: This study included 853 patients; 270 received conventional dose 3D-CRT, 314 received high-dose IMRT, 225 received BRT, and 44 received external beam radiotherapy (EBRT) + BRT boost. The median radiation doses were 68.4 grays (Gy) for 3D-CRT and 75.6 Gy for IMRT. BRT patients received a prescribed dose of 144 Gy with iodine-125 (I-125) or 120 Gy with palladium-103 (Pd-103), respectively. Patients treated with EBRT + BRT received 45 Gy of EBRT plus a boost of 110 Gy with I-125 or 90 Gy with Pd-103. Risk group categories were low risk (T1-T2 disease, prostate-specific antigen level <or=10 ng/mL, and a Gleason score <or=6), intermediate risk (increase in value of 1 of the factors), and high risk (increase in value of >or=2 factors).

Results: With a median follow-up of 58 months, the 5-year biochemical control (bNED) rates were 74% for 3D-CRT, 87% for IMRT, 94% for BRT, and 94% for EBRT + BRT (P <.0001). For the intermediate-risk group, high-dose IMRT, BRT, or EBRT + BRT achieved significantly better bNED rates than 3D-CRT (P <.0001), whereas no improvement was noted for the low-risk group (P = .22). There was no increase in gastrointestinal (GI) toxicity from high-dose IMRT compared with conventional dose 3D-CRT, although there was more grade 2 genitourinary (GU) toxicity (toxicities were graded at the time of each follow-up visit using a modified Radiation Therapy Oncology Group [RTOG] scale). BRT caused more GU but less GI toxicity, whereas EBRT + BRT caused more late GU and GI toxicity than IMRT or 3D-CRT.

Conclusions: The data from the current study indicate that radiation dose escalation improved the bNED rate for the intermediate-risk group. IMRT caused less acute and late GU toxicity than BRT or EBRT + BRT.