Choo, Richard

Purpose: This study aimed to compare long-term patient-reported outcomes in bowel and urinary domains between intensity-modulated radiotherapy (IMRT) and intensity-modulated proton therapy (IMPT) for localized prostate cancer. Methods and Materials: Patients with clinical T1–T2 prostate cancer receiving IMRT or IMPT at a tertiary cancer center from 2015–2018 were analyzed to determine the changes in the prospectively collected bowel function (BF), urinary irritative/obstructive symptoms (UO), and urinary incontinence (UI) domains of EPIC-26. The mean changes in EPIC-26 scores were evaluated from pretreatment to 24 months post-radiotherapy for each modality. A score change >50% of the baseline standard deviation was considered a clinically meaningful change. Results: A total of 82 patients treated with IMRT (52.2%) and 56 patients treated with IMPT (53.3%) completed the questionnaire at baseline and 24 months post-RT. There were no baseline differences in domain scores between treatment modalities. At 24 months post-radiotherapy, there was a significant and clinically meaningful decline in the BF mean score in the IMRT cohort (−4.52 (range −50, 29.17), p = 0.003), whereas the decline in BF score did not reach clinical relevance or significance (−1.88 (range −37.5, 50), p = 0.046) when accounting for the Bonferroni adjustment in the IMPT cohort. A higher proportion of patients treated with IMRT had a clinically relevant reduction in BF when compared with IMPT (47.37% vs. 25.93%, p = 0.017). The mean changes in the UI and UO scores of the IMRT and IMPT cohorts were neither statically significant nor clinically relevant. Conclusions: IMPT leads to a smaller decrease in BF than IMRT at 24 months post-RT, while there was no differential effect on UO and UI.

AbstractBackgroundThe objective of this study was to report acute changes in patient‐reported quality of life (PRQOL) using the 26‐item Expanded Prostate Index Composite (EPIC‐26) questionnaire in a prospective study using hypofractionated intensity‐modulated proton beam therapy (H‐IMPT) targeting the prostate and the pelvic lymph nodes for high‐risk or unfavorable intermediate‐risk prostate cancer.MethodsFifty‐five patients were enrolled. H‐IMPT consisted of 45 GyE to the pelvic lymph nodes and 67.5 GyE to the prostate and seminal vesicles in 25 fractions. PRQOL was assessed with the urinary incontinence (UI), urinary irritative/obstructive symptoms (UO), and bowel function (BF) domains of EPIC‐26 questionnaire. Mean changes in domain scores were analyzed from pretreatment to the end of treatment and 3 months posttreatment. A clinically meaningful change (or minimum important change) was defined as a score change > 50% of the baseline standard deviation.ResultsThe mean scores of UO, UI, and BF at baseline were 84.6, 91.1, and 95.3, respectively. At the end of treatment, there were statistically significant and clinically meaningful declines in UO and BF scores (−13.5 and −2.3, respectively), while the decline in UI score was statistically significant but not clinically meaningful (−13.7). A clinically meaningful decline in UO, UI, and BF scores occurred in 53.5%, 22.7%, and 73.2% of the patients, respectively. At 3 months posttreatment, all three mean scores showed an improvement, with fewer patients having a clinically meaningful decline in UO, UI, and BF scores (18.4%, 20.5%, and 45.0%, respectively). There was no significant reduction in the mean UO and UI scores compared to baseline, although the mean BF score remained lower than baseline and the difference was clinically meaningful.ConclusionsUO, UI, and BF scores of PRQOL declined at the end of H‐IMPT. UO and UI scores showed improvement at 3 months posttreatment and were similar to the baseline scores. However, BF score remained lower at 3 months posttreatment with a clinically meaningful decline.

Abstract Background Radium (Ra)‐223 is an established treatment option for patients with metastatic castrate‐resistant prostate cancer (mCRPC) who have symptomatic bone metastases without soft tissue disease. Studies have indicated genetic aberrations that regulate DNA damage response (DDR) in prostate cancer can increase susceptibility to treatments such as poly ADP‐ribose polymerase inhibitors and platinum‐based therapies. This study aims to evaluate mCRPC response to Ra‐223 stratified by tumor genomics. Methods This is a retrospective study of mCRPC patients who received Ra‐223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota) and Tulane Cancer Center. Patient demographics, genetic aberrations, treatment responses in terms of alkaline phosphatase (ALP) and prostate‐specific antigen (PSA), and survival were assessed. Primary end points were ALP and PSA response. Secondary end points were progression‐free survival (PFS) and overall survival (OS) from time of first radium treatment. Results One hundred and twenty‐seven mCRPC patients treated with Ra‐223 had germline and/or somatic genetic sequencing. The median age at time of diagnosis and Ra‐223 treatment was 61.0 and 68.6 years, respectively. Seventy‐nine (62.2%) had Gleason score ≥ 8 at time of diagnosis. 50.4% received prior docetaxel, and 12.6% received prior cabazitaxel. Notable alterations include TP53 (51.7%), BRCA 1/2 (15.0%), PTEN (13.4%), ATM (11.7%), TMPRSS2‐ERG (8.2%), RB deletion (3.4%), and CDK12 (1.9%). There was no significant difference in ALP or PSA response among the different genetic aberrations. Patients with a TMPRSS2‐ERG mutation exhibited a trend toward lower OS 15.4 months (95% confidence interval [CI] 10.0−NR) versus 26.8 months (95% CI 20.9−35.1). Patients with an RB deletion had a lower PFS 6.0 months (95% CI 1.28−NR) versus 9.0 months (95% CI 7.3−11.1) and a lower OS 13.9 months (95% CI 5.2−NR) versus 26.5 months (95% CI 19.8−33.8). Conclusions Among mCRPC patients treated with Ra‐223 at Mayo Clinic and Tulane Cancer Center, we did not find any clear negative predictors of biochemical response or survival to treatment. TMPRSS2‐ERG and RB mutations were associated with a worse OS. Prospective studies and larger sample sizes are needed to determine the impact of genetic aberrations in response to Ra‐223.

248 Background: Hypofractionated prostate cancer radiation has showed similar results in several prior phase III studies (PCG GU 003, PACE-B, and Hypo PC RT). However, prospective phase II-III clinical trial data testing 5 tx after prostatectomy is scarce. Methods: Between 2018 and 2019, 41 patients were treated after postprostatectomy for high risk features. 5 patients were treated adjuvantly, 36 for salvage including 8 with oligometastatic disease. Indications for adjuvant RT included a PSA < 0.2 and +margins, SVI, or EPE. Salvage RT was offered for PSA ≥0.2. Oligometastatic RT for patients with ≤5 RT targets. Staging included C11 PET for all cases. Total dose to the prostate bed was 30-32 Gy in 5tx QOD with IMRT, conebeam IGRT, and MRI registration. All salvage patients received ADT for 6 months and oligometastatic patients for 18 months. Dose to the metastatic sites was 30 in 5tx QOD. Of the 41 patients 8 also received SBRT to the sites of oligometastatic disease. We looked at clinical outcomes defining biochemical failure as a PSA > 0.2 after treatment, baseline adjusted CTC AE V5.0, baseline adjusted patient reported toxicities (PRO CTC AE), QOL (EPIC, PROMIS), and AUA was used for all cases. Results: Median follow up was 23 months (range 10-37). Pre-RT T stage was T2-T3b, with 47% being T3a-b; Pre RT Median PSA of 0.4 (range < 0.1-1.9); Median GS 8 (6-9); and (+) margins in 48.8%. Sites of oligometastatic disease radiated included the LN and bone. Treatment related AE were grade 0-1 in all cases, except for one patient with G2 GU incontinence. Overall QOL remained high during follow including Promis 10 overall, mental, and physical scores; urinary bother, irritative/obstructive, and AUA scores; bowel overall, bowel bother, and bowel function scores; and overall sexual, sexual function, and sexual bother scores remained at baseline levels during follow up. Only hormonal overall, hormonal function, and hormonal bother had lower scores at 3 months that recovered by 12 months in patients treated with ADT for 6 months and by 24 months in patients treated with ADT for 18 months. A total of 3 clinical failure have been seen; 2 patients with regional failures alone; and one with axial skeleton bony failures for 93% clinical control at median follow up of 23 months. All 3 patients with clinical failure were salvaged successfully with SBRT and all patients remain disease free at last follow up. A total 5 patients with raising PSAs alone have been seen. All patients have been re-staged with C11 PET. No failures in the prostate bed or previously radiated sites have been seen. Conclusions: Toxicity for RT over 5tx is lower than expected with only one case of grade 2 urinary incontinence. QOL scores remained high during follow up, minor changes in hormonal scores were seen during ADT, but recovered after. 30-32 Gy over 5 tx provided 100% control in radiated targets and metastatic sites. Clinical trial information: NCT03570827.

AbstractPurposeTo prospectively assess acute differences in patient‐reported outcomes in bowel and urinary domains between intensity‐modulated radiotherapy (IMRT) and proton beam therapy (PBT) for prostate cancer.Methods and MaterialsBowel function (BF), urinary irritative/obstructive symptoms (UO), and urinary incontinence (UI) domains of EPIC‐26 were collected in patients with T1‐T2 prostate cancer receiving IMRT or PBT at a tertiary cancer center (2015‐2018). Mean changes in domain scores were analyzed from pretreatment to the end of and 3 months post‐radiotherapy for each modality. A clinically meaningful change was defined as a score change >50% of the baseline standard deviation.ResultsA total of 157 patients receiving IMRT and 105 receiving PBT were included. There were no baseline differences in domain scores between cohorts. At the end of radiotherapy, there was significant and clinically meaningful worsening of BF and UO scores for patients receiving either modality. In the BF domain, the IMRT cohort experienced greater decrement (−13.0 vs −6.7, P < .01), and had a higher proportion of patients with clinically meaningful reduction (58.4% vs 39.5%, P = .01), compared to PBT. At 3 months post‐radiotherapy, the IMRT group had significant and clinically meaningful worsening of BF (−9.3, P < .001), whereas the change in BF score of the PBT cohort was no longer significant or clinically meaningful (−1.2, P = .25). There were no significant or clinically meaningful changes in UO or UI 3 months post‐radiotherapy.ConclusionsPBT had less acute decrement in BF than IMRT following radiotherapy. There was no difference between the two modalities in UO and UI.

e17587 Background: Radium (Ra)-223 has become the cornerstone treatment in patients with metastatic castrate-resistant prostate cancer (mCRPC) with bone metastases. Ra-223 has been shown to suppress abnormal bone formation by inducing DNA double-strand breaks in tumor cells. This can reduce skeletal-related events, as well as improve survival and quality of life. Studies have indicated mutations that regulate DNA damage response in prostate cancer as susceptible to PARP inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics. Methods: This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota). Patient demographics, genetic mutations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment. Results: 239 mCRPC patients treated with Ra-223 were identified. Germline and/or somatic genetic sequencing was available in 50 patients, who had a median age of 61 years at time of diagnosis and 68 years at time of Ra-223 treatment. Median Gleason score at time of diagnosis was 8.0. 100% of patients received prior androgen deprivation therapy. 72% received prior docetaxel, and 18% received prior cabazitaxel. Notable mutations included TP53 (45.2%), TMPRSS2-ERG (28.6%), PTEN (26.2%), BRCA1/2 (14.3%), ATM (9.3%), CDK12 (7.1%), and Rb (4.9%). TMPRSS2-ERG was the second most commonly found mutation, with median OS 12.7 mo versus 15.4 mo in patients without TMPRSS2-ERG mutations (p = 0.099). In patients with CDK12 mutations (2 of 28 tested positive), PFS was 10.4 mo versus 5.6 mo in patients without CDK12 mutations (p = 0.157). The assessment of ALP and PSA response to radium treatment stratified by genetic mutation did not reach statistical significance. Conclusions: Among mCRPC patients treated with Ra-223 at Mayo Clinic, TMPRSS2-ERG was the second most commonly found genetic mutation and had observed worse survival outcomes that approached statistical significance. Prospective studies and increased sample sizes are needed to determine the impact of genetic mutations in response to Ra-223.

4595 Background: For stage I-II testicular seminoma, RT is highly effective at eradicating disease in the abdominopelvic lymph nodes, but results in unnecessary exposure to normal tissues including the GI tract. The purpose of this study was to define the incidence and risk factors for late GI complications in this patient population. Methods: A retrospective review was performed of 251 patients with stage I-II testicular seminoma treated with curative intent RT at our institution from 1974-2009. All patients underwent orchiectomy and postoperative external beam RT to the involved and/or at-risk nodal basins. Potential late GI complications that were assessed included endoscopically-confirmed gastric or duodenal ulceration, small bowel obstruction (SBO), and biopsy-confirmed malignancy of the GI tract. Risks were estimated using the Kaplan-Meier (KM) technique and univariate/multivariate analyses were performed using the Cox proportional hazards model. Results: Median age at diagnosis was 36 years (range 18 – 80). Clinical stage was I (n=199) or II (n=52). Median abdominopelvic RT dose was 26 Gy (interquartile range 25 – 30). Median follow-up was 15 years (range 0.1 – 38). KM estimates for any GI complication (ulcer, SBO, or GI malignancy) at 10, 20, and 30 years were 7, 10 and 24%, respectively. Four patients died as result of a GI complication. KM estimates for ulcer at 10, 20, and 30 years were 4, 7, and 9%, respectively. Age at RT (Hazard Ratio [HR] 1.05, 95% Confidence Interval [CI] 1.00 – 1.10, p=0.03) and RT total dose (per Gy, HR 1.20, 95% CI 1.09 – 1.31, p<0.01) were associated with risk of ulcer. KM estimates for SBO at 10, 20, and 30 years were 2%, 2%, and 3%, respectively. History of inflammatory bowel disease was associated with risk of SBO (HR 43, 95% CI 7-325, p<0.01). KM estimates for GI malignancy at 10, 20, and 30 years were 0.5, 3 and 16%, respectively. Age at RT was associated with risk of GI malignancy (HR 1.07, 95% CI 1.02-1.14, p=0.01). Conclusions: In patients with stage I-II testicular seminoma treated with RT, late GI complications were a relatively uncommon, but clinically significant source of late morbidity. Use of low dose, limited field, and/or proton RT may reduce these risks.

14046 Background: LDM CTX is a minimally toxic anti-angiogenic therapy that has demonstrated activity in multiple tumour types including HRPC. Increased Cyclooxygenase 2 (COX 2, a prostaglandin synthase enzyme) expression appears to be a consistent feature of a variety of human tumours, including prostate cancer. COX 2 inhibitors like CEL exhibit anti-tumour activity in pre-clinical studies, at least in part due to their anti-angiogenic activity. Pre-clinical work supports the concept that the combination of selective angiogenesis inhibitors like CEL with metronomic chemotherapy can enhance the effects of these agents on tumour angiogenesis. Methods: Men with asymptomatic HRPC at a single Canadian centre received celecoxib 400 mg po BID and cyclophosphamide 50 mg po daily. The primary efficacy endpoint of this 2 stage phase II study is disease control rate (DCR): 50% PSA response, tumour response or prolonged (=6 mos) PSA or stable measurable disease. This study is also assessing the safety of LDM CTX and CEL as well as potential anti-angiogenic biomarkers in these patients including circulating endothelial cells and their precursors (CEC/P), plasma levels of thrombospondin-1 (TSP-1) and vascular endothelial growth factor (VEGF). Results: Enrollment for the first stage of this study (10 men) has been completed. There were 2 patients with disease control by the a priori criteria: one patient with a partial tumour response (PR) (PR duration 13 mos with PSA stabilization for 12 mos) and one patient that had both prolonged stable PSA (7 mos) and prolonged stable measurable disease (8 mos). In addition, another patient had an unconfirmed PR. The therapy was well tolerated. One patient had angina that responded well to medical therapy but there were no serious arterial-thromboembolic events. One patient developed grade 3 hypertension. All other toxicities were grade 1/2. Data on CEC/P, TSP-1 and VEGF levels will be presented at the meeting. Conclusions: LDM CTX + CEL is a well tolerated therapy in men with asymptomatic HRPC. 2/10 patients achieved disease control in the first stage of the trial, meeting the criteria to proceed to the second stage. [Table: see text]

5144 Background: The time course of testosterone (TST) recovery after prolonged androgen suppression (AS) is not well established. We examined TST recovery prospectively in prostate cancer (PCa) patients treated with 2 years of AS. Methods: 153 PCa men with pT3N0 or positive margins after radical prostatectomy (RP), or with PSA relapse (persistently detectable postoperative PSA [= 0.2 ng/mL], delayed detectable PSA = 6 months after surgery, or palpable/biopsy proven local recurrence after RP), were treated with radiation (RT) to the prostate bed (60 - 70 Gy in 30 - 35 fractions) plus 2 years of AS as part of a phase II study. AS consisted of nilutamide 100 mg PO tid for 4 weeks, starting within 1 week after completing RT, and busereline acetate 6.6 mg SC every 2 months for 2 years, starting within 2 weeks of nilutamide. The primary endpoint was PSA relapse-free survival. Serum TST levels were measured at baseline, every 4 months during AS, and every 6 months after completing AS. The planned sample size was 150 patients. Time to TST recovery was analyzed using the Kaplan-Meier method. Cox Proportional Hazards regression was used for a multivariate analysis of predictive factors for TST recovery. Results: 122 men completed the planned AS. Median follow up after finishing AS was 36.4 months (range 9.4 - 76.2). A castrate TST level was defined as =1.7 nmol/L (50 ng/dL), with normal levels being 10 - 40 nmol/L. All men achieved castrate TST levels on AS. Table 1 shows TST recovery at 36 months after completing AS and median times to recovery. Median recovery time to normal TST was 27 months, although 8% of men did not recover to above castrate levels by 3 years. On multivariate analysis, younger age (<60 vs. =60) predicted for a significantly shorter recovery time to normal TST (P = <0.0001), while baseline TST (<10 nmol/L vs. =10.0 nmol/L) was of borderline significance (P = 0.06). Conclusions: TST recovery after 2 years of AS is protracted. Older men have significantly longer recovery times. [Table: see text] [Table: see text]