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The management of local cancer recurrence within the prostate is challenging without a strong evidence base for guidance.  Surgical salvage post external beam or LDR brachytherapy carries significant risk of morbidity and requires an experienced surgeon.  Whole gland salvage with cryotherapy or HIFU has been advocated with variable success and high levels of treatment related toxicity reported.^{1, 2} With the advent of Choline -PET-CT at the Edinburgh Cancer Centre in 2015 helping to identify patients with a higher probability of  localised radio-recurrent disease within a heavily pre-treated gland , a protocol for focal salvage LDR brachytherapy was developed.  Here we report on our experience to date.

Patients were considered for focal salvage if they had no evidence of distant metastatic disease on bone scan and mpMRI and a subsequent Choline-PET-CT demonstrated unilateral recurrent disease alone. Patients were accepted on to the program if histology confirmed unilateral disease and they had grade 1 or less GI or GU post treatment toxicity form their initial radiation treatment.

Patients underwent a GA targeted template prostate biopsy i.e Cognisant targeted biopsy of the PET-CT lesion  (3 cores) and then systematic biopsy of the remaining prostate (12 cores) were taken.   An off line salvage focal brachytherapy plan was created aiming to cover the tumour PTV as determined by fusion of the PET-CT and TRUS volume study with the 200% isodose while keeping within standard rectal and urethral dose volume constraints.  Needle loading in the axial plain and seed disposition and needle tracking in the sagittal plan allowed real-time monitoring of the treatment dosimetry to ensure that the PTV and DVH constraints were met. Patients were followed up 3 monthly for year 1 and 4-6 monthly for years 2 and 3 then by 6-monthly thereafter. 

PSA relapse was determined by the standard Phoenix criteria of nadir plus 2ng/ml.

Data was collected retrospectively from electronic medical records and radiotherapy logs. A total of 15 patients treated between Jan 2015 to Jan 2020.

The median age of the cohort was 69 and the median follow up was 45 months.

A total of 15 patients were included who had undergone Salvage LDR Brachytherapy for locally recurrent Prostate Ca between Jan 2015 to Jan 2020.

The median age of the cohort was 69 and the median follow up was 45 months.

PSA relapse occurred in 4/15 patients with a median PSA relapse free survival of 38months.

Metastases and ADT free survival was 86.6% in our cohort.

Overall survival was 93.3%. There were no recorded toxicities of Grade 3 or over. 

Focal salvage brachytherapy is technically possible and in this selected group of patients the PSA relapse free survival  was promising. This also offers a novel way of delaying systemic treatments and preserving quality of life.  Longer follow up will be required to assess any impact on overall survival.