Citations

Abstract NRG-1 signals through epidermal growth factor receptor (EGFR) family members. Despite promising preclinical data, HER2 blockade in prostate cancer has failed to improve outcomes in clinical trials.1-4 We have discovered a novel complex systemic role of NRG-1 that drives sensitivity and resistance to androgen deprivation therapy (ADT) in castration-sensitive (CSPC) and castration resistant prostate cancer (CRPC), respectively. Significantly, sensitivity to ADT can be restored in CRPC by manipulating NRG-1 signaling. Our data posit NRG-1 as a systemic “switch” in prostate cancer. Plasma NRG-1 is elevated in our cohort of patients with metastatic CRPC (mean 4.9ng/ml) versus healthy controls (mean 3.2ng/ml, p<0.0001) or metastatic CSPC (mean 3.4ng/ml, p<0.0001). Paradoxically, high systemic NRG-1 predicted superior OS and PFS in CSPC but inferior clinical outcomes in CRPC. Consistently, opposite cell survival between LNCaP (CSPC) vs Du145 & PC3 (CRPC) was observed with recombinant human NRG-1 and enzalutamide (ENZ). ENZ combined with increasing NRG-1 concentration induced LNCaP cell death in an additive manner, but NRG-1 rescued Du145 & PC3 from ENZ-induced death in a dose-dependent manner. We next hypothesized that differential NRG-1 downstream signaling is mediated by engagement with distinct EGFR receptor dimers. While HER2 expression is similar, LNCaP express higher HER3 than Du145 & PC3. High ratio of HER2 to HER3 in Du145 & PC3 mirrors clinical reports of HER2 upregulation in CRPC5,6 and also predicts patient survival in the Stand Up to Cancer cohort.7 Significantly, we recapitulated the CRPC phenotype in LNCaP by inducing HER2 overexpression, HER3 suppression, and chemically-mediated HER2/HER3 dimerization. Conversely, HER2 knockdown sensitized Du145 cells to ENZ. Next, we queried composite single-cell whole human8 and CRPC9 transcriptomes for NRG-1 expression and discovered that the source of NRG-1 is the patients’ own mesenchymal stem cells (MSCs). Bone-derived MSC outgrowth cells produced copious NRG-1, which was increased substantially by coincubation with prostate cancer cell supernatants. Importantly, we were able to manipulate MSCs to reduce their NRG-1 production as a possible clinical translation. Similarly, patients treated with these compounds showed significant reduction in plasma NRG-1 levels after treatment. Additional clinical studies are pending. Together, our observations confirm that NRG-1 has differential signaling: HER3 homodimerization leads to prostate cancer cell death, whereas heterodimerization of HER3 with HER2 leads to prostate cancer cell survival via ADT resistance in a plasma NRG-1 dependent manner. Consequently, HER2 and HER3 receptor availability determine the molecular switch of NRG-1 in prostate cancer. Therefore, NRG-1 can be both a prognostic marker and therapeutic target in CRPC, and multiple clinical trials are pending. Citation Format: Jacob Orme, Roman Thaler, Dejie Wang, Siven Chinniah, Jacob Hirdler, Fernando Quevedo, Lance Pagliaro, Kwon Eugene, Alan Bryce, Brian Costello, Haojie Huang, Sean Park. Mesenchymal stem cell-derived systemic NRG-1 mediates a targetable molecular switch in metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 397.

e17036 Background: Elevated serum CGA is associated with an intrinsic or treatment-related neuroendocrine differentiation in men with mCRPC. We previously demonstrated that elevated serum CGA was negatively associated with OS in men with mCRPC. Fluctuations in serum CGA during mCRPC therapy is not well known. We analyzed the impact of (i) rising serum CGA and (ii) baseline CGA/PSA ratio during treatment to identify associations with AA therapy. Methods: Between June 2013 and August 2015, 92 men with mCRPC were enrolled in a prospective trial (“PROMOTE”; NCT#01953640) with uniform serum processing performed prior to initiating abiraterone acetate/prednisone (AA/P) and serially after 12 weeks of AA/P treatments. Serum CGA was measured using a homogenous automated immunofluorescent assay. Patients (pts) receiving proton pump inhibitors or with abnormal renal function were excluded due to possible false elevations of serum CGA (n = 21 excluded). All patients underwent a composite response assessment at 12-weeks with imaging/PSA/QOL questionnaires. Kaplan Meier estimates, and Cox Regression models were used to calculate association with time-to-treatment failure (TTF) analyses, defined as time from treatment initiation to AA/P discontinuation based on disease progression (BlueSky Statistics, Chicago, IL, USA). Results: Of the 71 eligible pts, 67/71 had paired baseline and 12-week CGA and 70/71 pts had a baseline and a 12-week PSA available. The median baseline CGA was 83.0ng/ml (range: 53.0 - 127.0 ng/ml), median baseline PSA was 14.4 ng/ml (range: 6.4-40.2 ng/ml), and the median TTF was 10 months (range: 6-25 months). The median CGA after 12 weeks of AA/P was 98.0 ng/ml (58.0 -148.0 ng/ml) and we observed a CGA rise in 41/67 (61.2%) pts. An increase in chromogranin was associated with a lower risk of treatment failure (HR: 0.52, p = 0.0181). The median CGA/PSA ratio was 7.8 (2.6 -16.0). An elevated pretreatment CGA/PSA ratio above the median was associated with a lower risk of treatment failure (HR: 0.54 p value = 0.0185). Conclusions: We show that an increasing chromogranin on AA/P and an elevated baseline CGA/PSA in pts with mCRPC were associated with a favorable response to AA/P. Further studies are needed to assess if rising CGA during therapy reflects neuroendocrine differentiation and may indicate a sign of treatment effect targeting the androgen susceptible cells. Clinical trial information: NCT#01953640.

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.

Abstract The second-generation antiandrogens have achieved an ever-growing list of approvals and indications in subsets of prostate cancer. Here, we provide an overview of second-generation antiandrogen trials and FDA approvals and outline a rational sequencing approach for the use of these agents as they relate to chemotherapy and other available treatment modalities in advanced prostate cancer. All published phase II-III randomized controlled trials reporting outcomes with the use of second-generation antiandrogens in prostate cancer are included as well as all published trials and retrospective studies of second-generation antiandrogen sequencing and/or combinations. Complete tabular and graphical representation of all available evidence is provided regarding the use and sequencing of second-generation antiandrogens in prostate cancer. In metastatic castration-resistant prostate cancer, evidence suggests prioritization of abiraterone before chemotherapy, chemotherapy after second-generation antiandrogen failure, and postchemotherapy enzalutamide in select patients to maximize agent efficacy and tolerability. We conclude that a rational, optimized sequencing of second-generation antiandrogens with other treatment options is feasible with present data.

Abstract Purpose: Outcomes for resistant metastatic castration-resistant prostate cancer (CRPC) are poor. Stereotactic ablative radiotherapy (SABR) induces antitumor immunity in clinical and preclinical studies, but immunologic biomarkers are lacking. Patients and Methods: Eighty-nine patients with oligometastatic CRPC were identified by 11C-Choline-PET (Choline-PET) from August 2016 to December 2019 and treated with SABR. Prespecified coprimary endpoints were 2-year overall survival (OS) and PSA progression. Secondary endpoints included 2-year SABR-treated local failure and 6-month adverse events. Correlative studies included peripheral blood T-cell subpopulations before and after SABR. Results: 128 lesions in 89 patients were included in this analysis. Median OS was 29.3 months, and 1- and 2-year OS were 96% and 80%, respectively. PSA PFS was 40% at 1 year and 21% at 2 years. Local PFS was 84.4% and 75.3% at 1 and 2 years, respectively, and no grade ≥3 AEs were observed. Baseline high levels of tumor-reactive T cells (TTR; CD8+CD11ahigh) predicted superior local, PSA, and distant PFS. Baseline high levels of effector memory T cells (TEM; CCR7−CD45RA−) were associated with improved PSA PFS. An increase in TTR at day 14 from baseline was associated with superior OS. Conclusions: This is the first comprehensive effector T-cell immunophenotype analysis in a phase II trial before and after SABR in CRPC. Results are favorable and support the incorporation of immune-based markers in the design of future randomized trials in patients with oligometastatic CRPC treated with SABR.

AbstractIntroductionChemotherapy in combination with immunotherapy has a proven survival benefit compared to chemotherapy alone in extensive stage small cell lung cancer (SCLC) and is the new standard of care. Since extrapulmonary small cell carcinomas (SCCs) are less common, treatment paradigms are reasonably extrapolated from SCLC regimens. We examined our institution's experience utilizing the combination of chemotherapy and immunotherapy (as used in SCLC) for SCC and neuroendocrine carcinoma of the prostate.MethodsUtilizing an institutional database search tool, we queried the electronic medical record to identify patients with SCC or neuroendocrine carcinoma of the prostate who had been treated with atezolizumab and chemotherapy. We recorded patient characteristics, including age, pathology, and disease extent. Treatment characteristics included number of prior treatments, use of concominant androgen deprivation, number of cycles of immunotherapy, and prior systemic therapies (including those for adenocarcinoma of the prostate). Progression free survival (PFS) and overall survival (OS) were the primary outcomes.ResultsWe identified seven men who received atezolizumab for metastatic prostate cancer with a small cell or neuroendocrine component. In six of the seven patients, the combination of carboplatin, etoposide, and atezolizumab was the first‐line of treatment after diagnosis of small cell or neuroendocrine carcinoma. Two of the seven patients had de novo small cell/neuroendocrine pathology, while the other five had transformation from a preexisting adenocarcinoma. In the patients who received chemotherapy plus immunotherapy in the first‐line setting, at a median follow‐up of 6.5 months (range: 1.5–15.1) the median PFS was 3.4 months and median OS was 8.4 months.ConclusionSmall cell or neuroendocrine carcinoma of the prostate was associated with poor survival outcomes despite adding immunotherapy (atezolizumab) to chemotherapy (carboplatin and etoposide). To our knowledge, there has been no demonstrable benefit of adding immunotherapy to chemotherapy in this setting.

Those with metastatic urothelial carcinoma generally respond more poorly to chemotherapy after they have progression on a checkpoint inhibitor (CPI). There is interest in combining CPIs with conventional cytotoxic chemotherapies as a strategy to exploit the efficacy and immunomodulatory effects of chemotherapy. We conducted a single institution, retrospective analysis including all patients treated between May 2018 and May 2020 with carboplatin and paclitaxel, concurrently or sequential with pembrolizumab, after having progression on a CPI alone. Clinical characteristics, response by RECIST 1.1, progression-free survival, and safety/tolerance of the treatment are reported. Median age was 80 years (64–85). Five patients (100%) had visceral metastases when starting carboplatin and paclitaxel. Chemotherapy was given with concurrent pembrolizumab (four patients) or following pembrolizumab (one patient) and continued until maximum response, significant toxicity, or progression. Two patients subsequently remained on maintenance pembrolizumab. There were four partial responses and one patient with stable disease. All patients on follow-up have progressed with median time to progression of 47 weeks (18–75). Two patients died from disease progression. This case series suggests that the combination of carboplatin, paclitaxel, and pembrolizumab leads to durable freedom from progression in some with metastatic urothelial cancer, who have progressed on a CPI alone. Larger studies of chemoimmunotherapy for metastatic urothelial carcinoma are warranted.

In 2013, the American Society of Hematology (ASH) published recommendations with Choosing Wisely to limit surveillance imaging in aggressive lymphoma. We studied surveillance imaging practice patterns for diffuse large B-cell lymphoma (DLBCL) before and after the ASH Choosing Wisely campaign. We used OptumLabs Data Warehouse, a national insurance claims database, to retrospectively study imaging frequency in survivors of DLBCL from 2008 to 2016. Three time periods were defined: Period 1 (2008 to 2010), Period 2 (2011 to 2013), and Period 3 (2014 to 2016). One thousand four hundred seventy-two patients were included. Median follow up was approximately 2 years. During the first and second years of surveillance, imaging remained stable between Period 1 (years 1 and 2: 199 [91%] and 137 [83%], respectively) and Period 2 (years 1 and 2: 257 [88%] and 172 [77%], respectively; P = .38), but decreased in Period 3 (years 1 and 2: 315 [78%] and 83 [61%], respectively; P < .01). In a multivariable logistic regression, year after 2012 was a significant predictor of decreased overuse (more than two scans per year in the first year of surveillance; [odds ratio, 0.49 for 2013 v 2008; P = .02]). Our study demonstrated the rate of surveillance scans—both computed tomography and positron emission tomography imaging—in DLBCL decreased after the ASH Choosing Wisely campaign. Multiple factors, such as changes in recommendations, reimbursement, and provider knowledge base, may have all contributed and should be studied further.

e20013 Background: Recent evidence suggests that patients with advanced cancer exhibit an underlying anti-tumor immune response that is continuously attenuated by regulatory T cells (Treg). Depletion of Treg using conventional chemotherapy may be feasible and clinically beneficial. C-reactive protein (CRP) is reported to rise/fall with initiation/termination of the immune response, and may be a surrogate for the periodicity of Treg proliferation that could be utilized for timing of anti-proliferative therapy. Timed delivery of chemotherapy therapy based on CRP cycling may deplete Treg and yield clinical benefit. Methods: We conducted a pilot clinical for 12 patients with metastatic melanoma who underwent serial CRP measurements (every 2–3 days) for 2 weeks. The CRP oscillation cycle was identified and chemotherapy with temozolomide (200mg/m2 for 5 days, every 28 days) was initiated at the estimated peak of plasma CRP. Patients were evaluated for clinical and immune response endpoints every 8 weeks until progression. Results: All 12 patients (median age 61; 4 female; 7 with M1c disease) exhibited oscillating CRP levels with an average periodicity of 7.8 days. Only 11 patients were treated (1 patient had rapid tumor progression). The two patients who remain progression-free for >2 years (1 PR, 1 CR), were treated in the pre-peak section of the CRP cycle, distinctly separate from the other patients treated post CRP-peak (all progressed <5 months). Presented are peripheral blood immunological laboratory correlates (cellular and cytokine) to CRP oscillation. Conclusions: These data suggest that patient clinical outcome may be dependent on the timing of therapy relative to an individual patient's immune response cycle and outline the dynamic equilibrium of systemic immune homeostasis in patients with advanced melanoma. Further investigations of these observations are under way. [Table: see text]

e16103 Background: At present, androgen ablation (AA) therapy ± radiation therapy represents a first-line treatment for patients with unresectable locally advanced prostate cancer (CAP), typically resulting in palliative disease control. Immunotherapy, in the form of CTLA-4 blockade, has been shown to potentiate T-cell responses, representing a potential antitumoral immunotherapy for treating CAP. Here, we discuss the outcomes of 5 locally advanced CAP patients treated with the monoclonal antibody MDX-CTLA-4 (MDX-010) + AA who subsequently underwent radical prostatectomy (RP), 2 of whom exhibited striking down-staging of their disease. Methods: A Phase II trial testing AA + MDX-010 therapy for treatment of locally or systemically advanced CAP is currently ongoing at our institution. To date, 5/85 patients have electively opted for off-study RP with extended pelvic lymphadenectomy after documentation of robust treatment response by PSA, staging digital rectal exam, and 3-D imaging. Results: All men had unresectable, locally advanced disease (stage T2c-T4) prior to treatment with AA + MDX-010 and subsequently underwent RP. Median blood loss was 400mL (400–900). All patients had negative surgical margins. Of the 5 patients, 2 exhibited dramatic and indisputable down-staging of their disease. These two patients presented with 80% of biopsies involved with cancer, extraprostatic extension, seminal vesicle (SV) invasion, and bladder base involvement. On final pathology, both exhibited extensive treatment effect, remission of SV involvement, and robust disaggregation of solid tumors resulting in only microscopic, non-contiguous foci of residual intraprostatic cancer. Both had T4 disease pre-treatment, and had stage T2c on final pathology. One patient is free of disease with undetectable PSA for 19 months following adjuvant radiation treatment but no further therapy, while the other patient is awaiting follow-up. Conclusions: We have been able to demonstrate true down-staging of locally advanced prostate cancer with neoadjuvant AA + MDX-010 therapy. This therapeutic modality exhibits significant promise for men with unresectable disease and may provide durable and potentially curative cancer control. No significant financial relationships to disclose.