Prognostic factors for late urinary toxicity grade 2-3 after conformal radiation therapy on patients with prostate cancer.

OBJECTIVE Identify prognostic factors associated to late urinary toxicity in patients with prostate cancer submitted to radical conformal radiotherapy (3DCRT). MATERIALS AND METHODS From July 1997 to January 2002, 285 patients with localized prostate cancer were consecutively treated with 3DCRT and retrospectively analyzed. Thirty seven (13%) patients were submitted to transurethral prostate resection previously to 3DCRT. The median dose delivered to the prostate was 7920 cGy (7020-8460). Patient and treatment characteristics were analyzed and correlated to late urinary toxicity grade 2-3, especially whether certain radiation doses applied to certain bladder volumes, when visualized through computerized tomography (CT) planning, correlated with the observed actuarial incidences of late urinary complications, using bladder volume as a continuous variable. RESULTS On a median follow-up of 53.6 months (3.6-95.3), the 5-year actuarial free from late urinary toxicity grade 2-3 survival was 91.1%. Seven and fifteen patients presented late urinary toxicity grades 2 and 3, respectively. Prior transurethral resection of prostate and radiation dose over 70 Gy on 30% of initial bladder volume were independent prognostic factors for late urinary toxicity grade 2-3. CONCLUSIONS This study suggests that restricting radiation doses to 70 Gy or less on 30% of bladder volume, visualized through CT planning, may reduce late urinary complications. It furthermore suggests that patients with prior transurethral resection of prostate may indicate a group of patients with a greater risk for late urinary toxicity grade 2-3 after 3DCRT.