Salvage SABR for a locally recurrent prostate cancer post 125I seed brachytherapy and ADT failure

Recurrences after LDR brachytherapy are known for prostate cancer. Second lines of treatment generally include surgery, cryotherapy, and androgen deprivation therapy. Re-irradiation is seldom prescribed as a treatment modality. Stereotactic ablative body radiotherapy (SABR) is an upcoming and accepted modality for low- and intermediate-risk prostate cancer. It offers conformity while delivering a high dose of radiation and limits the dose to the normal structure surrounding the target organ. In conjunction with other imaging modalities such as MRI and PET scans, accurate treatment delivery to the planning target volume is possible. SABR has not been documented as an alternative for a local recurrence or a relapse of prostate cancer. A 63-year-old male presented with urgency and poor urine flow. His PSA was 9.6 ng/dL, and his biopsy was indicative of adenocarcinoma prostate. He underwent I-125 brachytherapy, and his PSA after the procedure was 3.3 ng/dL. He underwent imaging and biopsy again in view of rising PSA levels (3.8 ng/dL and 8 ng/dL in two successive tests), and it showed a lesion in the prostate that was indicative of a recurrence. He was subsequently taken up for SABR to the prostate. After the bladder and rectal protocol, the patient was immobilized and a planning CT scan was obtained. The recent PET-CT scan and MRI images were fused with the simulation CT, and the lesion and the organs at risk were marked. The patient received 25 Gy in five fractions on alternate days. There was a near-complete reduction in the size of the prostate lesion that was noted in the PET-CT scan done for response assessment. PSA levels reduced to 0.28 ng/dL after 1 month of receiving radiotherapy, and his latest levels were 0.021 ng/dL. The patient had no early or late grade 2 or greater GI and GU toxicities. Salvage SABR is a feasible option in locally recurrent prostate cancer as a form of re-irradiation in selected cases.