Stereotactic body re-irradiation therapy for locally recurrent prostate cancer after external-beam radiation therapy: Initial report

Abstract

PurposeManagement of prostate cancer relapses after external-beam radiation therapy is still undefined. Re-irradiation schedules have been explored in different tumour sites. In this report, we present our preliminary experience of re-irradiation using stereotactic body radiotherapy for localized prostate cancer failure. Material and methodsBetween March 2011 and October 2014, robotic stereotactic body radiation therapy was administered to patients previously treated with external-beam radiation therapy to a median dose of 71.1Gy (range, 45–76.5Gy) and with biochemical failure corresponding to a local in-field recurrence of prostate cancer. Ten patients had recurrences after postoperative external-beam radiotherapy. Patients underwent a pelvic MRI to confirm the recurrence and a total body staging using a (18F)-fluorocholine PET/CT. The prescription dose consisted of five fractions of 7.25Gy to a total dose of 36.25Gy. Efficacy was evaluated based on biochemical response and toxicity was evaluated according to CTCAE v.4.0 questionnaires and International Prostate Symptom Score. ResultsTwenty-one patients were treated and followed for a median time of 11.7 months (mean: 13.4 months; range: 2.5–46.5 months). Median time between the first external-beam radiation therapy of prostate cancer and the first day of CyberKnife® treatment was 111 months (range: 38–398 months). One-year biochemical recurrence-free survival rate was 83.3%, and only one in-field progression was reported. Two patients had a biochemical failure corresponding to metastatic progression without evidence of local recurrence. Treatment was well tolerated, with only one grade 2 acute genitourinary toxicity, no grade≥2 acute gastrointestinal or late toxicities were reported. ConclusionStereotactic body re-irradiation therapy using CyberKnife® after failed external-beam radiation therapy showed favourable results in terms of in-field local and biochemical control. Toxicity was low and acceptable. Further prospective studies are needed to confirm these results to select patient and to evaluate the introduction of androgen-deprivation therapy.