Late toxicity after conformal and intensity-modulated radiation therapy for prostate cancer: impact of previous surgery for benign prostatic hyperplasia.

Objectives: To retrospectively compare late toxicity of conventional-dose three-dimensional conformal radiation therapy (3D-CRT) and high-dose intensity-modulated radiation therapy (IMRT) for prostate cancer.

Methods: A total of 340 patients with T1-3 prostate cancer were treated with 3D-CRT (n = 228) and IMRT (n = 112). The median follow-up time was 5.9 years and 3.0 years, respectively. The prescription dose was 70 Gy for 3D-CRT and 78 Gy for IMRT. Late gastrointestinal (GI) and genitourinary (GU) toxicities were graded according to the Fox Chase modification of the Radiation Therapy Oncology Group and Late Effects Normal Tissue Task Force criteria.

Results: There was no difference between 3D-CRT and IMRT in the incidence of GI and GU toxicity at 3 years. On multivariate analysis, transurethral resection of prostate/open transvesical prostatectomy (TURP/TVPE) for benign prostatic hyperplasia, carried out before radiotherapy, significantly increased the risk of Grade >or=2 GU toxicity (risk ratio 1.88). Among patients who experienced TURP/TVPE, the 5-year actuarial likelihood of Grade 2-3 urinary incontinence was 23%, compared with 9% for those without prostate surgery (P = 0.01).

Conclusions: Tolerance of 3D-CRT and IMRT was similar, despite the use of high radiation dose with IMRT. Previous TURP/TVPE increased the risk of GU toxicity.