PSOR7 Presentation Time: 12:00 PM: Toxicity and Efficacity of Whole Gland Salvage HDR Brachytherapy After Primary Radiation for Prostate Cancer

Abstract

<h3>Purpose</h3> Androgen Deprivation Therapy (ADT) is the most common treatment for relapsing prostate cancer after primary radiation therapy. However, an effective local treatment could be used to obtain local control of the disease while limiting the systemic side effects of ADT. We designed a single institution prospective pilot study to assess the efficacy and safety of whole gland prostate HDR brachytherapy. <h3>Materials and Methods</h3> Fifty (50) patients with local relapse after primary radiation therapy were included in this study. A biopsy-proven local relapse, a negative bone scan, and a negative CT scan of the abdomen and pelvis were mandatory. A dose of 32Gy in 4 fractions was delivered to the whole prostate by HDR brachytherapy using CT-based treatment planning. The use of ADT was allowed if deemed clinically indicated by the treating physician. The primary objective was to evaluate early and late gastrointestinal (GI) and genitourinary (GU) toxicities, assessed with CTCAE v5 scale and IPS score. Biochemical disease-free survival (bDFS) was evaluated as a secondary outcome. <h3>Results</h3> Median follow-up was 61,1 months (0.8-106.8 months). Sixteen (16) patients received short-course ADT prior to brachytherapy. GI toxicities were low, with no grade 3 toxicities reported. 4.1% and 14,6% of patients had early and late grade 2 toxicities. Only one patient had a grade 3 GU early toxicity. However, 16,7% of patients experienced late grade 3 toxicities (12.0% at the last follow-up). Interestingly, none of the patient using neoadjuvant ADT developed late grade 3 toxicities although this association was not statistically significant (Chi-Square p-value 0.171). Mean IPSS value presented a predictable rise to 15.9 at 1 month follow-up. A subsequent decline was observed to mean IPSS under 10 after 24 months. A bDFS of 73,5% was observed after 48 months. <h3>Conclusion</h3> Whole gland salvage HDR brachytherapy is an effective treatment with an excellent biochemical disease-free survival. However, it is associated with a significant risk of late GU toxicities. In this perspective, our treatment protocol has been modified to allow for focal therapy using MR guidance. That will allow us to evaluate if a similar local control can be maintained while reducing the incidence of severe toxicities.