Stereotactic prostate focal reirradiation therapy for local recurrence: preliminary results of Hartmann Oncology Radiotherapy Group

OBJECTIVE: Our objective was to report our experience and to evaluate the feasibility and toxicity of focal salvage stereotactic body radiation therapy (SBRT) in patients with post-radiation local recurrence of prostate cancer. METHODS: We retrospectively reviewed medical records of patients treated with Cyberknife (®) between October 2014 and April 2017 at our institution for a focal reirradiation delivered to the prostate/prostatic bed for local recurrence after radical or adjuvant radiotherapy. All patients underwent prostate biopsies at recurrence at the time of fiducial markers placement, had choline PET/CT and pelvic MRI. The treatment consisted in 36 Gy in six fractions delivered every other day. Post reirradiation toxicities were assessed according to the CTCAE v4 (Common Terminology Criteria for Adverse Events). RESULTS: 42 patients were treated with followed with a median follow-up of 21 months (range 3 – 31). 34 patients had biopsy proven recurrence. The initial treatment was radical prostatectomy and radiation therapy for 9 patients and radiation therapy alone for 33 patients. 23 patients from the group of prostate reirradiation had placement of rectal spacers. No Grade 4 or 5 toxicity were observed. 27 acute urinary events were recorded: 18 patients experienced Grade 1, 9 patients experienced Grade 2 toxicity and 1 patient experienced Grade 3 urinary toxicity, namely cystitis and/or dysuria. No Grade 2 or more digestive toxicity was observed. Rectal doses were significantly lower with rectal spacers. CONCLUSION: Salvage focal Cyberknife (®) seems feasible and show promising results. ADVANCES IN KNOWLEDGE: SBRT for local prostate cancer recurrence after initial radiotherapy is well tolerated with short follow-up.