Biochemical control and toxicity after intensity-modulated radiation therapy for prostate cancer.

Intensity modulated radiation therapy (IMRT) has achieved widespread use for prostate cancer; however, in relation to this use, outcomes studies are still relatively sparse. We report a single-institutional experience in outcomes analysis with the use of IMRT for the primary management of prostate cancer. One hundred thirty consecutive patients with adenocarcinoma of the prostate were treated at a single institution using IMRT with curative intent. Thirty-six (28%) patients were classified as low-risk, 69 (53%) as intermediate-risk, and 25 (19%) as high-risk. The median dose prescription was 76 Gy to the planning target volume. Sixty-five (50%) patients received androgen deprivation therapy (ADT) for a median 4 months, starting 2 months prior to IMRT. Biochemical failure was defined as PSA < post-treatment nadir+2. Gastrointestinal (GI) and Genitourinary (GU) toxicity were defined by RTOG criteria. Median follow-up was 53 months. By NCCN risk category, 4-year biochemical control was 97%, 94%, and 87% for low, intermediate, and high-risk patients, respectively. Among disease factors, multivariable analysis demonstrated the strongest association between biochemical control and Gleason score < or =6 (p=0.0371). Therapy was well tolerated with no Grade 4 toxicity and limited grade 3 GI or GU toxicity. Acute Grade 3+ GI and GU toxicity rates were 0% and 2%, and maximal late Grade 3+ GI and GU toxicity rates were 5% and 6%, respectively. Late rectal toxicity was associated with higher volumes of RT to the rectum. By last follow-up late Grade 3+ toxicity was 2% for both GI and GU systems. In conclusion, patients treated with IMRT for prostate cancer have excellent rates of biochemical control and low rates of severe toxicity of treatment.