GTV Boost for Prostate Cancer: Early Comparison of Patient-Reported QoL with MR-Linac vs HDR Brachytherapy

Purpose MR-guided high dose rate (HDR) brachytherapy for focal GTV boost in prostate cancer radiotherapy is an established technique. However, this is resource-intense, invasive and may be contraindicated in some patients. Linear accelerators with integrated MRI allow visualization of the GTV within the prostate, facilitating the use of External Beam Radiation Therapy (EBRT) to deliver GTV boost. This study compared patient-reported quality of life for the first 20 patients treated with these two techniques. Methodology Twenty intermediate risk prostate cancer patients who were enrolled and treated between May 2022 and August 2023 in prospective clinical trials were included in this study. Patients were stratified based on patient preference; 10 patients received GTV boost fraction using HDR brachytherapy and 10 patients were treated with EBRT using a 1.5T MR-Linac. For HDR treatment patients were positioned supine under general anesthesia while transperineal catheters were inserted under MRI guidance. For EBRT treatment patients were positioned supine with minimal immobilization and an empty bladder. All patients received 1 × 15 Gy to the GTV followed within 1 week by 5 × 6 Gy (alternate days) to the whole prostate. Both groups received their subsequent whole gland prostate treatment on the MR-Linac. Patient-reported quality of life was captured using The Expanded Prostate Cancer Index Composite (EPIC) survey. The questionnaire was administered at baseline and at one month follow-up. Results were analyzed using descriptive statistics. Results All patients completed treatment as planned and had minimum follow up of 1 month (range 1-6). The mean score and standard deviation collected from EPIC for bladder and bowel subscales at 1-month follow up were similar between those who received HDR and EBRT with 81.1(29.7) and 94.1 (13.9) vs 85.2(23.1) and 93.9(15.0) respectively. There were also no statistically significant differences when looking further at additional subsets, urinary function was 87.7(13.1) vs 89.8(8.3), p=1.0 for HDR and EBRT and urinary bother 74.2(21.8) vs 81.63(11.0), p=0.71. Bowel function was 94.3(6.2) vs 92.9(8.3), p=1.0 for HDR and EBRT and bowel bother 93.9(7.5) vs 94.8(8.8), p=0.62. The mean change in score from baseline assessment was –5.7 for urinary incontinence and –6.1 urinary irritative/obstructive and 0.8 in rectal subscales for HDR patients compared to 1.0, -1.9 and 0.0 for EBRT patients. These changes from baseline only exceeded the minimally important difference (MID) reported in literature for the urinary irritative/obstructive subscale and only in HDR patients. Conclusions MRL focal boost to GTV region of the prostate was found to have a similar patient-reported quality of life compared to HDR focal boost at 1 month following completion of treatment, although patients receiving HDR reported a MID from baseline in urinary irritative/obstructive symptoms. A larger sample size may confirm these preliminary findings translate into differences in QOL.