PO75

Purpose The purpose of this study is to determine the efficacy of high dose-rate brachytherapy as a single modality treatment in patients with low and intermediate risk prostate cancer in a community setting. Materials and Methods Data was collected from 114 patients who were consecutively treated and received high dose-rate brachytherapy monotherapy for low and intermediate risk prostate cancer from 01/18/2017 to 12/14/2021. Patients had a median age at the start of treatment of 69, with a mean of 68.09 and range of 46 to 95 years. The clinical stage for all patients was T1c, with seventy-four (64.91%) patients having a Gleason score of 3+3=6, thirty-seven (32.46%) having a Gleason score of 3+4=7, and three (2.63%) having a Gleason score of 4+3=7. No patients exhibited perineural invasion and only five (4.39%) had 50% or more cores positive. The pretreatment PSA levels of all patients were between 2.2 and 17.5 ng/mL, with a median and mean of 5.8 and 6.7 ng/mL, respectively. Patients were administered either 3,800 cGy in two, three, or four fractions or 3,600 cGy in four fractions using HDR Iridium-192 as the radiation source. 104 patients (91.23%) received a dose of 3,800 cGy in four equal fractions, one patient (0.88%) in three equal fractions, and four patients (3.51%) in two equal fractions. Five patients (4.39%) received a dose of 3,600 cGy in four fractions. Patients receiving four fractions were given two fractions per day, two weeks apart, while patients receiving two fractions were given one fraction per day, two weeks apart. Following treatment, patients had scheduled follow-ups every three to six months after treatment to determine PSA levels. Results Post-treatment PSA levels were recorded for 108 patients, and this data was used to calculate a cure rate using the Phoenix definition of biochemical failure: a rise in PSA level 2.0 ng/mL above nadir. The definition used for a benign bounce is a rise in PSA level followed by a subsequent decrease in PSA level by greater than or equal to 0.5 ng/mL. PSA nadirs were recorded an average of 544.52 days after the end of treatment. There was a range of 85 to 1099 days and a median of 538.5 days. The average post-treatment PSA nadir was 0.83 ng/mL with a median of 0.50 ng/mL and range of less than 0.01 ng/mL to 4.51 ng/mL. Twenty-one (19.44%) of patients achieved a nadir value between 0.5 and 1.0 ng/mL, and fifty-one (47.22%) achieved a nadir value of below 0.5 ng/mL. Two patients experienced biochemical failure according to the Phoenix definition, as their PSA level rose 2.0 ng/mL above nadir with no subsequent decrease, resulting in a 98.15% success rate. Conclusions High dose-rate brachytherapy as a single modality treatment is successful in a community setting in treating low and intermediate risk prostate patients. The purpose of this study is to determine the efficacy of high dose-rate brachytherapy as a single modality treatment in patients with low and intermediate risk prostate cancer in a community setting. Data was collected from 114 patients who were consecutively treated and received high dose-rate brachytherapy monotherapy for low and intermediate risk prostate cancer from 01/18/2017 to 12/14/2021. Patients had a median age at the start of treatment of 69, with a mean of 68.09 and range of 46 to 95 years. The clinical stage for all patients was T1c, with seventy-four (64.91%) patients having a Gleason score of 3+3=6, thirty-seven (32.46%) having a Gleason score of 3+4=7, and three (2.63%) having a Gleason score of 4+3=7. No patients exhibited perineural invasion and only five (4.39%) had 50% or more cores positive. The pretreatment PSA levels of all patients were between 2.2 and 17.5 ng/mL, with a median and mean of 5.8 and 6.7 ng/mL, respectively. Patients were administered either 3,800 cGy in two, three, or four fractions or 3,600 cGy in four fractions using HDR Iridium-192 as the radiation source. 104 patients (91.23%) received a dose of 3,800 cGy in four equal fractions, one patient (0.88%) in three equal fractions, and four patients (3.51%) in two equal fractions. Five patients (4.39%) received a dose of 3,600 cGy in four fractions. Patients receiving four fractions were given two fractions per day, two weeks apart, while patients receiving two fractions were given one fraction per day, two weeks apart. Following treatment, patients had scheduled follow-ups every three to six months after treatment to determine PSA levels. Post-treatment PSA levels were recorded for 108 patients, and this data was used to calculate a cure rate using the Phoenix definition of biochemical failure: a rise in PSA level 2.0 ng/mL above nadir. The definition used for a benign bounce is a rise in PSA level followed by a subsequent decrease in PSA level by greater than or equal to 0.5 ng/mL. PSA nadirs were recorded an average of 544.52 days after the end of treatment. There was a range of 85 to 1099 days and a median of 538.5 days. The average post-treatment PSA nadir was 0.83 ng/mL with a median of 0.50 ng/mL and range of less than 0.01 ng/mL to 4.51 ng/mL. Twenty-one (19.44%) of patients achieved a nadir value between 0.5 and 1.0 ng/mL, and fifty-one (47.22%) achieved a nadir value of below 0.5 ng/mL. Two patients experienced biochemical failure according to the Phoenix definition, as their PSA level rose 2.0 ng/mL above nadir with no subsequent decrease, resulting in a 98.15% success rate. High dose-rate brachytherapy as a single modality treatment is successful in a community setting in treating low and intermediate risk prostate patients.