Phase I/II study of stereotactic ablative radiotherapy including regional lymph node irradiation for patients with high-risk prostate cancer (SATURN): Early results.

Abstract

264 Background: Dose escalation using five-fraction stereotactic ablative radiotherapy (SABR) is gaining popularity in the treatment of prostate cancer. This has not been extensively tested in the context of pelvic radiation for high-risk groups. The objectives of study are to report early toxicity and quality of life outcomes in patients following 5-fraction prostate and pelvic radiation. Methods: A phase I/II study was performed where high-risk prostate cancer patients (T3a-3b or Gleason score ≥ 8 or PSA > 20ng/ml) received 40Gy to prostate and 25Gy to pelvis and seminal vesicles in 5 weekly fractions, on a gantry-based platform. A 3mm planning target volume margin to the prostate and a 6mm margin to the lymph nodes was applied. Image guidance was performed using gold seed fiducials and cone beam computerized tomography. Androgen deprivation therapy (ADT) was used for 12-18 months. Common Terminology Criteria for Adverse Events version 3.0 was used to assess toxicities at 3- and 6-months. Quality of life data (QOL) was captured using EPIC questionnaire. A minimally clinically important change (MCIC) definition was triggered if the EPIC QOL score decreases > 0.5 SD, where SD is the standard deviation of baseline scores. Results: Thirty patients completed the planned treatment with a median follow up of 11.9 months (IQR 8.3, 13.0). The following toxicities were observed: grade 2 genitourinary (GU): 50% at 3 months and 34.5% at 6 months; grade 2 gastrointestinal (GI): 3.3% at 3months and 6.9% at 6 months. No ≥ grade 3 toxicities were observed. Mean (95% Confidence Interval) EPIC urinary QOL scores were 86.6 (81.9-91.3), 87.1(81.4-92.6) and 86.1(80.2-92.0) at baseline, 3 months and 6 months and the bowel scores were 94.1(91.3-97.0), 93.2(89.1-97.2) and 93.2(89.5-96.8), respectively. Proportion of patients experiencing MCIC at 3 months and 6 months were 27.8% and 31.8% for urinary domain, 23.5% and 28.6% for bowel domain; respectively. Conclusions: This gantry-based novel fractionation schedule incorporating pelvic radiation for high-risk prostate cancer in combination with ADT is feasible and well tolerated in the acute setting. Clinical trial information: NCT 01953055.