Acute and Late Adverse Effects of Prostate-Only or Pelvic Stereotactic Radiation Therapy in Prostate Cancer: A Comparative Study

Abstract

To compare the urinary and gastrointestinal adverse effects with or without the inclusion of pelvic nodal regions in patients treated with extreme hypofractionated stereotactic radiation therapy (SBRT) for prostate cancer. Patients treated with definitive SBRT for nonmetastatic adenocarcinoma prostate were identified from prospectively maintained institutional database, and details of radiation therapy volume, dose, acute, and late adverse effects were analyzed. Symptoms of acute (within 90 days of completing SBRT) and late gastrointestinal and urinary toxic effects were graded using Common Terminology Criteria for Adverse Effects version 5.0. Each symptom was scored according to the worst reported grading during treatment and the follow-up period. Cumulative rates of adverse effects between prostate-only SBRT (PO-SBRT) and whole pelvic SBRT (WP-SBRT) were compared using the χ2 test. Univariable and multivariable analysis was performed for possible factors affecting acute gastrointestinal and late urinary toxic effects. A total of 220 patients were analyzed (PO-SBRT = 118, WP-SBRT = 102), with a median follow-up of 28 months (interquartile range, 14-40). Most patients had locally advanced disease (PO-SBRT 60% high risk and 40% intermediate risk, WP-SBRT 79% node positive, and 21% high risk). The median SBRT dose was 36.25Gy (interquartile range, 35-36.25) to the prostate (2-Gy equivalent, EQD2 = 90.6Gy, a/b = 1.5Gy) and simultaneous integrated 25Gy to the pelvis (EQD2 = 46.3Gy) in 5 fractions on alternate days. No grade 3 to 4 acute adverse effects were observed except 1 grade 3 urinary obstruction (PO-SBRT). WP-SBRT was associated with a significantly higher rate of acute grade 2 gastrointestinal toxic effects (29.4% vs 14.7%, P = .008) and late grade 2 urinary adverse effects (45.6% vs 25.0%, P = .003). Both groups had low incidence of late grade 3 adverse effects (urinary 2.5%, gastrointestinal 1%). WP-SBRT was associated with significantly higher acute gastrointestinal and late urinary adverse effects compared with PO-SBRT, although overall incidence of severe adverse effects was low.