PO73

Abstract

Purpose To identify a predictive factor associated with local recurrence in prostate cancer patients receiving HDR brachytherapy. Materials and Methods Localized, non-metastatic prostate cancer patients who were treated with brachytherapy with or without external beam radiation (EBRT) between January 2015 to December 2021 were retrospectively reviewed. HDR monotherapy was prescribed at 19 Gy to prostate while HDR brachytherapy was prescribed at 15 Gy to prostate after EBRT of 45-50 Gy to whole pelvis. Factors to identify a predictor of local recurrence included prostate volume, dominant intraprostatic lesion (DIL) volume, PSA density and DIL-concentrated PSA (DILcPSA). DILcPSA is defined as the PSA density within the area of DIL volume which can be calculated by PSA density multiplied by DIL volume. Baseline patient characteristics and tumor characteristics were reported. Univariate and multivariate analysis were performed to identify factors associated local recurrence by using Cox's regression analysis. Results 32 patients with the median follow up time of 59.2 months were included. The median age of patients was 70 years. Most patients were categorized as unfavorable to very high risk (19 patients, 59.4%); however, most common grade group was grade group 2 (14 patients, 43.7%). Most patients received androgen deprivation therapy (ADT) either by medication or surgical castration (25 patients, 78.1%). The proportion of patients underwent HDR brachytherapy as monotherapy (18 patients, 56.2%) was similar to as a boost (14 patients, 43.8%). For tumor characteristics, most of DILs were located at peripheral zone (28 patients, 87.5%). Median DIL volume and prostate volume were 1.13 ml (95%CI 0.78 to 1.48), and 39.4 ml (95%CI 31.38 to 47.42), respectively. Median PSA density and DILcPSA were 0.30 (95%CI 0.12 to 0.48) and 0.33 (95%CI 0.15 to 0.51), respectively. There were 9 patients developed local recurrence. The rate of 5-year local recurrence-free survival was 68.5%. Among factors selected to predict local recurrence, DILcPSA was found to be significantly associated with local recurrence for both univariate and multivariate Cox's regression analysis with HR of 2.10 (95%CI 1.12 to 27.67) p=0.035 and 2.06 (95%CI 1.09 to 27.41) p 0.039, respectively. Prostate volume, DIL volume and PSA density were found no significant correlation with local recurrence. Conclusions DILcPSA could be a potential predictive factor to predict local recurrence in prostate cancer patients receiving HDR brachytherapy. To identify a predictive factor associated with local recurrence in prostate cancer patients receiving HDR brachytherapy. Localized, non-metastatic prostate cancer patients who were treated with brachytherapy with or without external beam radiation (EBRT) between January 2015 to December 2021 were retrospectively reviewed. HDR monotherapy was prescribed at 19 Gy to prostate while HDR brachytherapy was prescribed at 15 Gy to prostate after EBRT of 45-50 Gy to whole pelvis. Factors to identify a predictor of local recurrence included prostate volume, dominant intraprostatic lesion (DIL) volume, PSA density and DIL-concentrated PSA (DILcPSA). DILcPSA is defined as the PSA density within the area of DIL volume which can be calculated by PSA density multiplied by DIL volume. Baseline patient characteristics and tumor characteristics were reported. Univariate and multivariate analysis were performed to identify factors associated local recurrence by using Cox's regression analysis. 32 patients with the median follow up time of 59.2 months were included. The median age of patients was 70 years. Most patients were categorized as unfavorable to very high risk (19 patients, 59.4%); however, most common grade group was grade group 2 (14 patients, 43.7%). Most patients received androgen deprivation therapy (ADT) either by medication or surgical castration (25 patients, 78.1%). The proportion of patients underwent HDR brachytherapy as monotherapy (18 patients, 56.2%) was similar to as a boost (14 patients, 43.8%). For tumor characteristics, most of DILs were located at peripheral zone (28 patients, 87.5%). Median DIL volume and prostate volume were 1.13 ml (95%CI 0.78 to 1.48), and 39.4 ml (95%CI 31.38 to 47.42), respectively. Median PSA density and DILcPSA were 0.30 (95%CI 0.12 to 0.48) and 0.33 (95%CI 0.15 to 0.51), respectively. There were 9 patients developed local recurrence. The rate of 5-year local recurrence-free survival was 68.5%. Among factors selected to predict local recurrence, DILcPSA was found to be significantly associated with local recurrence for both univariate and multivariate Cox's regression analysis with HR of 2.10 (95%CI 1.12 to 27.67) p=0.035 and 2.06 (95%CI 1.09 to 27.41) p 0.039, respectively. Prostate volume, DIL volume and PSA density were found no significant correlation with local recurrence. DILcPSA could be a potential predictive factor to predict local recurrence in prostate cancer patients receiving HDR brachytherapy.