Steen, Preston D.

5004 Background: Patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC) treated continuously with testosterone suppression (TS) plus an androgen receptor pathway inhibitor (ARPI) can experience cumulative toxicity. We conducted this single-arm phase 2 trial (NCT05241860) to test the hypothesis that pts who achieve favorable response to TS + ARPI can have prolonged treatment-free interval with testosterone recovery after treatment interruption (TI). Here we report on the primary endpoint. Methods: Eligible pts had mHSPC by conventional imaging with prostate-specific antigen (PSA) ≥ 5 ng/ml and testosterone ≥ 150 ng/dl prior to starting TS+ARPI, with PSA < 0.2 ng/ml and testosterone < 50 ng/dl at the time of enrollment after having received TS for 540-750 days and ARPI for ≥ 360 days. Prior local therapy, radiation to metastases and docetaxel were permitted. After enrollment, pts discontinued TS and ARPI and were followed with PSA and testosterone levels every 3 months (mo), CT/MRI and bone scan at least every 6 mo, and FACT-P questionnaire for patient-reported outcomes (PROs) every 6 mo. Treatment was resumed for PSA ≥ 5 ng/ml, radiographic change (progressive disease [PD] per RECIST 1.1 on CT/MRI or unconfirmed PD per PCWG3 on bone scan), or prostate cancer-related symptoms. The primary endpoint was proportion of men remaining treatment-free 18 mo after TI with eugonadal testosterone ( > 150 ng/dl). Target enrollment was 75 pts to differentiate 18-mo treatment-free rates of 0.30 (H 0 ) and 0.45 (H a ). Results: Of 79 pts enrolled between 07/2022 and 03/2024, 78 were eligible and underwent TI. Among these 78, median PSA prior to starting TS+ARPI was 19 (range 5-6759), 27 (35%) had high volume disease, 31 (40%) never received local therapy, and 55 (71%) did not receive radiation to metastases. By 18 mo after TI, 67% (52/78) recovered testosterone and 58% (45/78) remained treatment-free; 41% (32/78) remained treatment-free with testosterone recovery (80% CI 33.5-48.9%, one-sided p 0.0249). At median follow-up of 21.2 mo, 35% (27/78) resumed initial TS+ARPI after meeting re-initiation criteria (of whom 1 required treatment switch for PD 9 mo later); 5% (4/78) resumed prior to meeting criteria; 9% (7/78) pursued alternative therapy instead of resuming TS+ARPI per protocol; 5% (4/78) withdrew; 1 died of myocardial infarction prior to resuming treatment. 4 pts died, 1 of prostate cancer. Conclusions: The primary objective was achieved with 41% of favorable responders to TS+ARPI remaining treatment-free with testosterone recovery at 18 mo after TI. Analyses of biomarkers and PROs are in progress, and pts will be followed for long-term outcomes. Support: U10CA180821, U10CA180882, UG1CA189823, https://acknowledgments.alliancefound.org, Veracyte Inc. Clinical trial information: NCT05241860 .

TPS5118 Background: Novel androgen receptor pathway inhibitors (ARPIs) improve overall survival (OS) in patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC) in conjunction with testosterone suppression (TS) relative to TS alone. However, the duration of treatment required to derive clinical benefit is unclear, as is whether continuous treatment is requisite for optimal cancer outcomes. Favorable PSA declines have been associated with prolonged OS in clinical trials testing TS + ARPIs. We thus designed this single-arm Phase 2 trial to test the hypothesis that pts who achieve exceptional response to upfront TS + ARPI can suspend treatment, allowing for T recovery and improvement in quality of life while maintaining favorable clinical outcomes. Methods: Eligible pts had mHSPC by conventional imaging with PSA ≥ 5 ng/ml and T ≥ 150 ng/dl (or not known to have been hypogonadal) prior to starting treatment, have been receiving TS for 540-750 days and ARPI for ≥ 360 days, and have achieved PSA < 0.2 ng/ml (stable or falling for 3 consecutive measurements) with castrate T <50 ng/dl at the time of enrollment. Intermittent ADT for biochemical recurrence prior to mHSPC diagnosis, prior local therapy, prior radiation to metastatic sites, and up to 6 cycles of docetaxel in mHSPC are permitted. Pts who underwent surgical castration, received ARPI prior to mHSPC diagnosis, or are receiving experimental treatment for mHSPC or participating in a clinical trial that does not allow for TS or ARPI interruption are excluded. After enrollment, pts discontinue both TS and ARPI and are followed with PSA and T levels every 3 months, conventional CT/MRI and bone scan at least every 6 months, and FACT-P questionnaire for patient-reported outcomes every 6 months. Treatment re-initiation triggers are PSA increase to ≥ 5 ng/ml, radiographic change (progressive disease per modified RECIST 1.1 on CT/MRI or unconfirmed progressive disease per PCWG3 on bone scan), or symptoms attributable to prostate cancer. Subsequent management is per physician discretion. The primary endpoint is remaining treatment-free with eugonadal T (> 150 mg/dl) 18 months after the start of treatment interruption, with 75 pts to be enrolled to differentiate 18-month treatment free rates of 0.30 (null hypothesis) and 0.45 (alternative hypothesis). Secondary endpoints include time to eugonadal T, duration off treatment, and changes in patient-reported outcomes. Exploratory endpoints include radiographic progression-free survival, time to next treatment, OS, and correlation of tissue- and blood-based biomarkers with clinical endpoints. The study was activated in July 2022 and accrual is ongoing throughout the NCTN. Support: U10CA180821, U10CA180882, UG1CA189823, https://acknowledgments.alliancefound.org , Veracyte Inc. Clinical trial information: NCT05241860 .

Abstract Background: Despite evidence of substantial breast cancer risk reduction, few high-risk women adopt chemopreventive medications such as selective estrogen receptor modulators (SERMs) or aromatase inhibitors (AIs). Women with benign breast disease, such as atypical hyperplasia (AH) or lobular carcinoma in situ (LCIS), have an increased risk of developing breast cancer and derive a greater benefit from antiestrogens compared to other high-risk women. Reasons for low uptake of chemoprevention include insufficient patient and clinician knowledge about antiestrogens, time constraints during the clinical encounter, and concerns about side effects. To address these barriers, we have developed patient and provider web-based decision support tools to improve informed choice about breast cancer chemoprevention among women with AH or LCIS. Study design: We are conducting a cluster-randomized controlled trial of clinical decision support to improve chemoprevention informed choice among women with AH or LCIS and their treating providers. Twenty-six U.S. sites through the SWOG Cancer Research Network were randomly assigned 1:1 to standard educational materials alone or in combination with the patient-centered decision aid (RealRisks) and provider decision support tool (BNAV). A total of 415 patients and 200 healthcare providers will be recruited from these sites. RealRisks consists of interactive modules to calculate personalized breast cancer risk and elicit preferences on chemoprevention. The modules are available in English and Spanish. BNAV is comprised of self-directed case-based learning modules on breast cancer risk assessment and chemoprevention. Patients complete questionnaires at baseline, 6 and 12 months. Providers complete surveys at baseline and after their enrolled patient’s 6-month clinical encounter. The primary endpoint is chemoprevention informed choice at 6 months, using a measure combining knowledge, attitude, and intention scales. Secondary endpoints include perceived breast cancer risk/worry, chemoprevention knowledge/intention, decision conflict/regret, shared decision-making, and chemoprevention uptake. For patients who begin chemoprevention, adherence and reasons for discontinuation are assessed annually for up to 5 years. Barriers and facilitators to implementing RealRisks and BNAV into clinic workflow will be assessed by conducting patient and provider interviews at baseline and mid-implementation. Eligibility criteria: Eligible patients include women, age 35-74 years, with AH or LCIS, no history of breast cancer, no prior use of SERMs or AIs, no bilateral mastectomies, English or Spanish-speaking, and access to the internet. Eligible providers include breast surgeons, medical oncologists, primary care providers, and physician extenders who see patients with AH or LCIS. Statistical methods: We have 90% power to detect a 15% increase in the frequency of chemoprevention informed choice with a 1-sided 0.025 level test, assuming an intraclass correlation (ICC) of 0.02 to account for clustering, roughly equal accrual at each site, 10% loss to follow-up, and ≤10% event rate in the control arm. Current/target accrual: The trial was activated on 9/1/2020. As of 7/7/2022, all 26 sites have been randomized, 157/200 providers and 184/415 patients have been enrolled. Discussion: Our hybrid effectiveness/implementation study seeks to evaluate the effectiveness of a multi-level intervention in promoting informed decision-making about breast cancer chemoprevention. Study results will provide valuable insights on how the decision support tools are integrated in diverse clinical settings. Citation Format: Katherine D. Crew, Garnet Anderson, Kathryn Arnold, Andrew Stieb, Jacquelyn N. Amenta, Cynthia Law, Ana Sandoval-Leon, Sarah Colonna, Tari King, Debra Mangino, Sandhya Pruthi, Maria Grosse Perdekamp, Christa Braun-Inglis, Stacy Krisher, Lisa Yee, Danielle Bertoni, Samantha Seaward, Kari B. Wisinski, Justin Floyd, Corrine Zarwan, Tarah J. Ballinger, Lindi VanderWalde, Masey M. Ross, Preston Steen, Shelly Lo, Alison Conlin, Kathleen Yost, John Ellerton, Erin Lin, Holly J. Pederson, Sagar Sardesai, Cheryl Jernigan, Dawn Hershman, Marian L. Neuhouser, Banu K. Arun, Rita Kukafka. SWOG 1904: Cluster-randomized controlled trial of patient and provider decision support to increase chemoprevention informed choice among women with atypical hyperplasia or lobular carcinoma in situ (MiCHOICE) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-15-01.

TPS4615 Background: While a standard approach to muscle-invasive bladder cancer (MIBC) management involves neoadjuvant cisplatin-based chemotherapy (NAC) followed by radical cystectomy (RC), up to 50% of pts recur with metastatic disease. Moreover, removal of the bladder has a significant impact on pts’ quality of life. Pathologic downstaging to non-muscle-invasive disease (<pT2) or complete response (pT0) at RC is associated with long-term survival benefit. Somatic DDR gene alterations were shown to be enriched in pts who were pT0 at RC following NAC in multiple retrospective analyses. We hypothesize that MIBC pts with somatic loss-of-function alterations within specific DDR genes and clinical responses to NAC can be uniquely managed with a bladder-sparing approach consisting of close cystoscopic and radiographic surveillance, avoiding the toxicities of definitive local therapy. Methods: A031701 is a multicenter phase II trial that will enroll 271 pts with T2-T4aN0/xM0 MIBC diagnosed within 60 days prior to enrollment. Multifocal MIBC, tumors >5 cm by cystoscopic assessment, and Bacillus Calmette-Guérin (BCG)-refractory disease (beyond standard induction and maintenance) are not allowed. Intravesical chemotherapy is allowed. Pts must be eligible for cisplatin chemotherapy. Eligible pts will receive either standard dose or dose dense gemcitabine and cisplatin chemotherapy (investigator’s choice) with simultaneous genetic sequencing of pre-treatment transurethral resection specimens. Pts whose tumors contain deleterious alterations in any 1 of 9 pre-selected DDR genes ( ERCC2, ERCC5, BRCA1, BRCA2, RECQL4, RAD51C, ATM, ATR, and FANCC) and who exhibit <T1 response on clinical restaging are eligible for organ-sparing management. Pts without deleterious DDR gene alterations or with >T1 disease after NAC will undergo RC or chemoradiation therapy (investigator/patient choice). The primary endpoint is 3-year event-free survival in DDR-altered pts who undergo bladder sparing, defined as the proportion of pts without BCG-unresponsive non-muscle invasive recurrences, any >T2 recurrences, or any metastatic recurrences. Secondary endpoints include clinical response rate (<cT1) in patients with deleterious DDR gene alterations following NAC, bladder-intact survival, overall survival, pT0 rate in DDR-altered pts who elect to undergo RC, pT0 rate in pts without DDR gene alterations, 3-year RC rate in pts with DDR gene alterations, and proportion of pts undergoing intravesical management for in-bladder recurrences. The study opened for enrollment in September 2018. Support: U10CA180821, U10CA180882. Clinical trial information: NCT03609216.

2562 Background: Empiric chemotherapy (taxane/platinum) is standard for CUP. Because prognosis is poor, novel approaches are needed. The PI3K/mTOR pathway is frequently dysregulated in cancer. Everolimus (E), an mTOR inhibitor, is approved for multiple malignancies. We performed a phase II study of Pac + Carb + E as first-line therapy in metastatic CUP patients (pts). We additionally determined if a gene expression profiling (GEP) test that identifies tissue of origin (Pathwork Tissue of Origin) could identify responsive pts. (NCT00936702) Methods: Newly diagnosed, untreated CUP pts were eligible. Central pathology review confirmed CUP prior to registration; GEP was performed on formalin fixed tumor tissue. Pac (200 mg/m2), Carb (AUC=6) and E (30 mg once weekly) were delivered every 3 wks until progression or intolerable adverse events (AEs). The primary endpoint was confirmed response, with ≥11 of 50 responses (22%) needed for trial success. Secondary endpoints were OS, progression-free survival (PFS) and AEs. Results: 46 pts (median age 61) received a median 4 cycles (range: 1-33). 39 (85%), 21 (46%) and 1 (2%) experienced ≥1 grade (gr) 3+, 4+, or 5 (sepsis) AE, with gr 3+ hematologic AE most common (74%). Of 44 evaluable pts, 15 had a confirmed response (RR 34%, 95% CI: 21-50%), with a median PFS and OS of 4.1 and 10.1 mos, respectively. Adequate tissue for GEP was available in 36 pts and predicted 10 different sites of origin. In pts with a predicted tissue of origin in which taxane/platinum is standardly used, higher RR and significantly longer PFS and OS were observed compared with pts whose GEP identified a malignancy where taxane/platinum is not standard (Table). Conclusions: In pts with untreated CUP, Carb +Pac +E demonstrated promising antitumor activity. The GEP test identified patients clinically responsive to Carb/Pac/E therapy, and may be useful to select CUP pts for specific antitumor regimens. Clinical trial information: NCT00936702. [Table: see text]

271 Background: Epidermal growth factor inhibitors show some benefit in the treatment of advanced pancreatic cancer. A trial to evaluate the incorporation of Pmab into a conventional multimodality regimen and continuation as maintenance therapy was conducted in pts with LA disease. Methods: Pts with ECOG PS 0-1, preserved organ function and tumor encompassed within standard radiation fields were eligible. Pmab 6 mg/kg on days 1, 15, 29 and continuous infusion 5-FU 225 mg/m2/d or capecitabine 825 mg/m2 were given with RT. Pts then received weekly gemcitabine 1000 mg/m2 and Pmab on days 1, 15 for three 4-week cycles. Maintenance Pmab was then continued for additional 6 months. RT consisted of 45 Gy to the tumor and regional nodes with a 5.4 Gy boost using conformal techniques. Primary endpoint of one-year survival (OS) with secondary endpoints progression-free survival (PFS), confirmed tumor response, and adverse events (at least possibly related) are reported. Results: 51 pts (23 M: 28 F) were enrolled with a median age of 65 (range: 43-84). Twenty-two pts (43%) received at least 1 cycle of post-chemo-RT, while 29 patients only received chemo-RT. All 51 pts have ended treatment with pts going off study because of: progression (39%), adverse events (27%), refusal (25%), and other reasons (8%). Frequently occurring maximum grade 3/4 AEs across the entire treatment course (chemo-RT + post-chemo-RT chemo) are shown below. With a median follow-up of 12.3 months, survival at 12 months is 50.2% (95% CI: 37.9-66.5%), median survival 12.1 mos (95% CI: 6.8-15.9) and median PFS 7.4 mos (95% CI: 3.7-8.6). Confirmed response rate was 5.9% (1-CR, 2-PR). Conclusions: The addition of Pmab to a conventional chemo-RT regimen provides benefit in terms of median survival. This is similar to reports of other EGFR inhibitors in LA disease. Adverse events, especially during the chemo-RT portion, were considerable and affected administration of subsequent systemic maintenance therapy. [Table: see text]

CRA9015 Background: Hot flashes are a common symptom during the menopause transition or following breast cancer treatment that can negatively impact the quality of life for many women. Preliminary data have suggested that flaxseed, a rich source of dietary lignans, may be a potentially effective treatment for hot flashes. Methods: A phase III randomized, placebo controlled trial was conducted to evaluate the efficacy of flaxseed in reducing hot flashes. Postmenopausal women were randomly assigned to a flaxseed bar (providing 410 mg of lignans) for 6 weeks vs a placebo bar. Participants completed daily prospective, self report hot flash diaries during the baseline week and then began eating one study bar per day for 6 weeks, while continuing to record their daily hot flashes. The intra-patient difference in hot flash activity between baseline and the last treatment week was the primary endpoint. Side effects of the bars were evaluated through self report and CTC assessment. Results: Between October and December 2009, 188 women were enrolled onto this trial. Mean hot flash scores were reduced by 4.9 units in the flaxseed group and 3.5 in the placebo group (p=0.29). In both groups, a little over a third of the women received a 50% reduction in their hot flash scores. Only one side effect was significantly different between groups, that being grade 1 pruritis, which was more common (7%) in the placebo group versus 1% in the flaxseed group. Both groups reported increased abdominal distension, flatulence, diarrhea and nausea. Adherence and ability to detect treatment assignment did not differ between groups. Conclusions: The results of this trial do not support the use of 410 mg of flaxseed lignans for the reduction of hot flashes. The gastrointestinal side effects seen in both groups were likely due to the fiber content in the flaxseed and placebo bars.

Abstract Background: Treatment of aromatase refractory metastatic breast cancer (MBC) is difficult and challenging. Estrogen receptor (ER) resistance causes enhanced expression of the vascular endothelial growth factor (VEGF).Several studies have shown that the ER interacts with the VEGF pathway and is an important mechanism of resistance. Therefore we embarked on a phase II study of fulvestrant, a complete ER suppressor and bevacizumab, a well studied VEGF monoclonal antibody in aromatase refractory MBC patients. Methods: A single stage phase II study with an interim analysis of fulvestrant and bevacizumab was conducted with these objectives: 6 month progression-free survival rate (PFS), tumor response, toxicity, and overall survival. Regimen: fulvestrant 250 mg day1 and 15 (cycle 1) then day 1 (cycle 2 and beyond) and bevacizumab 10mg/kg days 1 and 15 of each 4 weeks is a cycle. Results: At the time of interim analysis, 11/20 evaluable patients achieved 3-month progression-free survival status while remaining on treatment for at least 3 months, not meeting the protocol specified efficacy requirements and thus halting accrual. 36 patients were enrolled from September 2007-December 2008; 33 patients were evaluable. Number of prior metastatic chemotherapy regimens: 0 in 26 patients and 1 in 7 patients. 22 (67%) patients received prior hormonal therapy in the metastatic setting. 18 (55%) had measurable disease. A median of 6 cycles (range 1-19) were administered. 12/33 evaluable patients (95% CI:20-55%) achieved 6-month progression-free survival status while remaining on treatment for a least 6 months. Among 18 patients with measurable disease, 2 (11%) patients CI:1.4-35%) had a confirmed tumor reponse (both PR). Additionally, 2 patients had stable disease for greater than 6 months, for a clinical benefit rate of 22%. Median follow up was 8.5 months (range 1.7-17.5 months). Median progression-free survival was 6.2 months (95% CI:5.4-10.1 months). The 6 -month overall survival rate was 84.8% (95% CI 73.5-98%). The median dose level administered was 250 mg for fulvestrant and 10 mg/kg for bevacizumab for cycles 1-19. The most common grade 3/4 adverse events (AEs) were hypertension 2 (6%), headache pain 2 (6%), and confusion 2 (6%). There was 1 grade 5 central nervous system hemorrhage. 13 (39%) patients experienced a grade 3 non-hematologic AE and 4 (12%) experience a grade 4+ non-hematologic AE. Conclusion: Fulvestrant/bevacizumab is safe and tolerable. Although this regimen did not meet its statistical endpoint, 22% of evaluable patients with aromatase refractory diesease achieved clinical benefit with minimal toxicity. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4096.