Radiation dose escalation for localized prostate cancer

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 ≤10 ng/mL, and a Gleason score ≤6), intermediate risk (increase in value of 1 of the factors), and high risk (increase in value of ≥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. Cancer 2009. © 2009 American Cancer Society.