Stereotactic Prostate Focal Re-Irradiation Therapy for Local Recurrence

Abstract

Optimal management of patient with recurrent prostate cancer after primary radiation remains controversial. Our objective was to report our experience and to evaluate the feasibility and toxicity of focal salvage stereotactic body radiation therapy in patients with post-radiation local recurrence of prostate cancer. We retrospectively reviewed medical records of patients treated with Cybeknife® between October 2014 and May 2016 at our institution for a re irradiation delivered to the prostate/prostatic bed for local recurrence after radical or adjuvant radiotherapy. All patients underwent prostate biopsies at recurrence concomitant with fiduciary set and had choline PET/CT. The treatment consisted in 36 Gy in 6 fractions delivered every other day. Dosimetric data were collected in the whole cohort. Post re irradiation toxicities were assessed according to the CTCAE v4. Forty-two patients were treated with a median follow-up of 20 months (range 12-35). 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. Twenty-three patients from the group of prostate re-irradiation had placement of rectal spacers. Eight patients have received androgen deprivation therapy associated with salvage therapy for a mean duration of 6 months. The median PSA level at the time of salvage therapy was 3.1 (range 0.01-23.7). No grade 4 or 5 toxicity were observed. Twenty-seven 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. Salvage focal robotic radiosurgery is feasible and show promising results.