Real-World Experience with 177Lu-PSMA-617 Radioligand Therapy After Food and Drug Administration Approval

We report our initial real-world experience with 177Lu-PSMA-617 radioligand therapy. Methods: We performed a retrospective review of patients treated with 177Lu-PSMA-617. Pretreatment PSMA PET, laboratory findings, overall survival, a fall in prostate-specific antigen by 50% (PSA50), and toxicities were evaluated. Results: Ninety-nine patients were included. Sixty patients achieved a PSA50. Seven of 18 (39%) patients who did not meet the TheraP PSMA imaging criteria achieved a PSA50. Nineteen of 31 (61%) patients who did not meet the VISION laboratory criteria achieved a PSA50. Sixty-three patients had a delay or stoppage in therapy, which was due to a good response in 19 patients and progressive disease in 14 patients. Of 10 patients with a good response who restarted treatment, 9 subsequently achieved a PSA50 on retreatment. The most common toxicities were anemia (33%) and thrombocytopenia (21%). Conclusion: At our center, patients who did not meet the TheraP PSMA imaging criteria or the VISION laboratory criteria benefited from 177Lu-PSMA-617 radioligand therapy.

Diagnosis and management of neuroendocrine prostate cancer

BACKGROUND

Although most patients with prostate cancer (PC) respond to initial androgen deprivation therapy (ADT), castration-resistant disease invariably develops. Progression to treatment-emergent neuroendocrine PC (t-NEPC) represents a unique mechanism of resistance to androgen receptor (AR)-targeted therapy in which lineage plasticity and neuroendocrine differentiation induce a phenotypic switch from an AR-driven adenocarcinoma to an AR-independent NEPC. t-NEPC is characterized by an aggressive clinical course, increased resistance to AR-targeted therapies, and a poor overall prognosis.

METHODS

This review provides an overview of our current knowledge of NEPC, with a focus on the unmet needs, diagnosis, and clinical management of t-NEPC.

RESULTS

Evidence extrapolated from the literature on small cell lung cancer or data from metastatic castration-resistant PC (mCRPC) cohorts enriched for t-NEPC suggests an increased sensitivity to platinum-based chemotherapy. However, optimal strategies for managing t-NEPC have not been established, and prospective clinical trial data are limited. Intertumoral heterogeneity within a given patient, as well as the lack of robust molecular or clinical biomarkers for early detection, often lead to delays in diagnosis and prolonged treatment with suboptimal strategies (i.e., conventional chemohormonal therapies for mCRPC), which may further contribute to poor outcomes.

CONCLUSIONS

Recent advances in genomic and molecular classification of NEPC and the development of novel biomarkers may facilitate an early diagnosis, help to identify promising therapeutic targets, and improve the selection of patients most likely to benefit from NEPC-targeted therapies.

Initial Experience with 68Ga-FAP-2286 PET Imaging in Patients with Urothelial Cancer

Improved imaging modalities are needed to accurately stage patients with muscle-invasive bladder cancer (MIBC) and metastatic urothelial carcinoma. Imaging with small-molecule ligands or inhibitors of fibroblast activation protein (FAP) is a promising modality that has demonstrated initial efficacy across a broad range of tumors. We present our experience with the novel FAP-peptide binder 68Ga-FAP-2286 in patients with MIBC. Methods: Patients with histopathologically confirmed bladder cancer who had either localized disease at diagnosis (localized cohort, n = 13) or known metastatic disease (metastatic cohort, n = 8) were imaged with 68Ga-FAP-2286 PET as part of a clinical trial (NCT04621435). The SUVmax of 68Ga-FAP-2286 PET-positive lesions and lesion size were documented. In patients who had available 18F-FDG PET performed within 45 d of 68Ga-FAP-2286 PET (n = 5), uptake on the 2 scans was compared. When there was a discrepancy between imaging modalities on retrospective review, biopsy of suggestive lesions was performed as the standard of care. Results: In the metastatic and localized cohorts, 36 and 18 68Ga-FAP-2286-avid lesions, respectively, were identified across multiple anatomic locations, including lymph nodes, visceral metastases, and bones. Fourteen of 36 lesions in the metastatic cohort and 14 of 18 lesions in the localized cohort were lymph nodes measuring less than 1 cm. Among lesions measuring less than 0.5 cm, 0.5-1 cm, and more than 1 cm, average SUVmax was 5.2 ± 2.6, 9.6 ± 3.7, and 13.0 ± 4.3, respectively, in the metastatic cohort and 10.5 ± 5.1, 10.8 ± 5.7, and 9.9 ± 5.4, respectively, in the localized cohort. Five patients had 18F-FDG PET available for comparison. The average SUVmax for lesions avid on 68Ga-FAP-2286 PET and 18F-FDG PET was 9.9 ± 3.4 versus 4.2 ± 1.9, respectively (n = 16 lesions). For 3 patients in the localized cohort, 68Ga-FAP-2286 PET informed clinical management, including identification of both false-positive findings on 18F-FDG PET and false-negative findings on conventional CT. Conclusion: 68Ga-FAP-2286 imaging is highly sensitive in patients with urothelial cancer and is effective in identifying metastatic lesions across a variety of anatomic sites, including subcentimeter lymph nodes that would not have raised suspicion on conventional scans. This novel imaging modality may inform clinical decision-making in patients with MIBC both by refining local nodal staging and by defining metastatic disease that would otherwise be undetectable on conventional imaging.

Single-dose 177Lu-PSMA-617 followed by maintenance pembrolizumab in patients with metastatic castration-resistant prostate cancer: an open-label, dose-expansion, phase 1 trial

BACKGROUND

Checkpoint inhibitors have been shown to have limited activity in patients with metastatic castration-resistant prostate cancer. We aimed to determine whether a single dose of lutetium-177 [177Lu]-prostate-specific membrane antigen (PSMA)-617 (177Lu-PSMA-617) followed by maintenance pembrolizumab was safe and could induce durable clinical benefit.

METHODS

We did an open-label, dose-expansion, phase 1 study at the University of California, San Francisco (San Fransisco, CA, USA). Eligible patients were men aged 18 years or older with progressive metastatic castration-resistant prostate cancer who had an Eastern Cooperative Oncology Group performance status of 0 or 1, had progression on one or more androgen signalling inhibitors, and at least three PSMA-avid lesions on 68Ga-PSMA-11 positron emission tomography. In part A, patients were enrolled sequentially to one of three schedules in which a single dose of 177Lu-PSMA-617 (7·4 GBq) was given intravenously 28 days before (schedule 1), concomitant with (schedule 2), or 21 days after (schedule 3) the start of maintenance intravenous pembrolizumab (200 mg every 3 weeks). In part B, 25 patients were enrolled using the recommended phase 2 schedule. The primary endpoint in part A was determination of the recommended phase 2 schedule, and in part B, the objective response rate. The analysis set included all patients who received at least one dose of pembrolizumab or 177Lu-PSMA-617. This study is registered with ClinicalTrials.gov, NCT03805594.

FINDINGS

Between Aug 8, 2019 and May 7, 2022, 43 male patients were enrolled (n=18 part A [six patients per schedule]; n=25 part B), with a median follow-up of 16·5 months (IQR 12·2-21·9). Schedule 1 was selected as the recommended phase 2 schedule for part B, on the basis of safety and feasibility of administration observed in part A. In part B, 14 (56%; 95% CI 35-76) of 25 patients had a confirmed objective response. Two (5%) of 43 patients had a treatment-related adverse event of grade 3 or worse (grade 3 arthritis in schedule 2, grade 3 pneumonitis in schedule 3). One serious adverse event (one death due to aspiration pneumonia) and no treatment-related deaths were observed.

INTERPRETATION

A single priming dose of 177Lu-PSMA-617 followed by pembrolizumab maintenance was safe and had encouraging preliminary activity in patients with metastatic castration-resistant prostate cancer.

FUNDING

Prostate Cancer Foundation, National Cancer Institute, Novartis Pharmaceuticals, and Merck.

Impact of Squamous Histology on Clinical Outcomes and Molecular Profiling in Metastatic Urothelial Carcinoma Patients Treated With Immune Checkpoint Inhibitors or Enfortumab Vedotin

INTRODUCTION

Urothelial carcinoma with squamous differentiation (UCS) is associated with increased resistance to chemotherapy, but outcomes associated with newer therapies approved in this space over the last 5 to 10 years are less well defined. We investigated clinical outcomes and molecular profiling of patients with UCS treated with an immune checkpoint inhibitor (ICI) and/or Enfortumab vedotin (EV).

PATIENTS AND METHODS

We undertook a retrospective analysis of UC patients treated with ICI and/or EV. Objective response rate (ORR), progression free survival (PFS) and overall survival (OS) were compared between pure UC (pUC) and UCS using X2 and log-rank tests, respectively. Prevalence of the most commonly detected somatic alterations were also compared between the 2 histologic subgroups.

RESULTS

A total of 160 patients (40 UCS, 120 pUC) were identified for this analysis. Among 151 patients treated with ICI (38 UCS, 113 pUC), UCS patients had a shorter mPFS (1.9 vs. 4.8 months, P < 0.01) and mOS (9.2 vs. 20.7 months, P < 0.01) compared to pUC. Among 37 patients treated with EV (12 UCS, 25 pUC), UCS patients had a lower ORR (17% vs. 70%, P < 0.01) and shorter mPFS (3.4 vs. 15.8 months, P < 0.01). UCS samples were enriched for CDKN2A, CDKN2B, PIK3CA, while pUC samples were enriched for ERBB2 alterations.

CONCLUSION

In this single-center retrospective analysis, patients with UCS had a distinct somatic genomic profile relative to patients with pUC. Patients with UCS also had inferior outcomes to ICIs and EV compared to patients with pUC.

Somatic alterations of TP53 and MDM2 associated with response to enfortumab vedotin in patients with advanced urothelial cancer

Background

Enfortumab vedotin (EV) is an antibody-drug conjugate approved for patients with treatment-refractory advanced urothelial carcinoma (aUC), however data on biomarkers of response is lacking.

Methods

We retrospectively identified all aUC patients at our institution who received EV monotherapy and had next-generation sequencing (NGS) data available. Patients were considered responders if they had a complete response or partial response on restaging scans during treatment. Observed response rate (ORR) was evaluated by local investigator and compared between responders and non-responders using Chi-squared test. A univariable analysis was conducted using the Cox proportional hazard test to assess for associations between baseline characteristics and most common somatic alterations (in ≥10% of patients) with patient survival outcomes [progression-free survival (PFS) and overall survival (OS)]. Somatic alterations were then individually evaluated in separate multivariate models while accounting for patient and clinical characteristics using Cox regression models.

Results

Among 29 patients treated with EV monotherapy, 27 had available NGS data. Median age was 70, 24 (83%) were men, 19 (62%) were Caucasian, 15 (52%) had pure urothelial histology and 22 (76%) had primary tumor in the bladder. ORR was 41%, and PFS and OS for the overall cohort were 5.1 months and 10.2 months. Responders were enriched among patients with TP53, KDM6A and MDM2 alterations. Patients with these alterations, as well as those with composite TP53/MDM2 alterations (alterations in either TP53 or MDM2), also had increased ORR with EV treatment compared to patients without these alterations. In the univariable analysis, baseline albumin level ≥ 3.0g/dL and presence of composite TP53/MDM2 alterations were associated with a prolonged OS. Baseline ECOG 0/1, TP53 alterations and TP53/MDM2 alterations were associated with a prolonged PFS. In the multivariable analysis, TP53 and TP53/MDM2 alterations were genomic markers predictive of improved PFS after accounting for the relevant clinical characteristics.

Conclusion

In this single-center retrospective analysis of aUC patients treated with EV, presence of TP53 or MDM2 somatic alterations, lower ECOG PS scores (ECOG 0 or 1) and higher albumin levels (≥3 g/dL) were associated with improved outcomes with EV treatment. Prospective and external validation of these findings in larger cohorts is warranted.

Serial stereotactic body radiation therapy for oligometastatic prostate cancer detected by novel PET-based radiotracers

BACKGROUND

Radiopharmaceuticals, including Ga-68-prostate specific membrane antigen (PSMA)-11 and F-18-Fluciclovine, are increasingly used to inform therapies for prostate cancer (CaP). Stereotactic body radiation therapy (SBRT) to PET-detected oligometastatic CaP has been shown to improve progression free survival (PFS) and delay androgen deprivation therapy (ADT) compared to observation. For men who subsequently develop oligorecurrent CaP, outcomes following second SBRT are unknown.

METHODS

A retrospective cohort study was conducted. Eligibility criteria included patients with oligometastatic (1-5 lesions) CaP detected on PSMA or Fluciclovine PET who underwent 2 consecutive SBRT courses to tracer-avid sites. Data on stage, tracer type, concurrent systemic therapy, and prostate-specific antigen (PSA) responses for first SBRT (SBRT1) and second SBRT (SBRT2) were collected. Outcomes included PSA decline ≥50% (PSA50), PFS after SBRT2, and ADT initiation or intensification-free survival after SBRT2. Factors potentially associated with PSA50 after SBRT2 was evaluated with multivariable logistic regression. Factors potentially associated with PFS and ADT initiation/intensification-free survival after SBRT2 were evaluated with separate multivariable Cox proportional-hazards models.

RESULTS

Twenty-five patients were identified. At SBRT2, oligorecurrence was detected on PSMA and Fluciclovine PET in 17 (68%) and 8 (32%) patients, respectively. Fifteen (60%) patients had castration-sensitive disease and 10 (40%) had castration-resistant disease. After SBRT2, 16 (64%) achieved a PSA50 response, median PFS was 11.0mo, and median ADT initiation/intensification-free survival was 23.2mo. On multivariable analysis, maximum percent change in PSA after SBRT1 (OR 0.94, 95%CI 0.88-0.99, P = 0.046) and concurrent change in systemic therapy (OR 21.61, 95%CI 1.12-417.9, P = 0.042) were associated with PSA50 responses after SBRT2. PSA50 response after SBRT1 was associated with improved PFS (HR 0.36, 95%CI 0.00-0.42, P = 0.008) and ADT initiation/intensification-free survival (HR 0.07, 95%CI 0.01-0.68, P = 0.021) after SBRT2. From SBRT1 to last follow-up (median 48 months), 7 (28%) patients remained ADT-free.

CONCLUSIONS

Serial SBRT for oligometastatic CaP detected on PSMA or Fluciclovine PET is feasible and can achieve PSA declines, with or without systemic therapy. Degree of biochemical response to first SBRT warrants further study as a potential predictor of PSA response, PFS, and ADT initiation/intensification-free survival following a subsequent SBRT course. This preliminary evidence provides rationale for larger, prospective studies of this strategy.

Association of biomarkers and outcomes in patients (pts) with metastatic urothelial carcinoma (mUC) treated with immune checkpoint inhibitors (ICIs)

532

Background: ICIs form the backbone of treatment for mUC. However, only a minority of pts benefit and additional biomarkers of ICI response are needed. Methods: In our institution, we identified mUC pts treated with ICI monotherapy who had next generation sequencing (NGS). Somatic alterations present in ≥10% of pts ( ARID1A, CCND1, CDKN2A, CDKN2B, ERBB2, FGF3, FGF4, FGF19, FGFR3, KDM6A, MDM2, MLL2, PIK3CA, RB1, TERTp, TP53, TSC1), as well as DNA-damage response (DDR) alterations and tumor mutational burden (TMB) were analyzed as biomarkers. These biomarkers were individually evaluated in separate multivariate models while accounting for clinical factors including age, BMI, ECOG PS, primary tumor location, histology, hemoglobin, neutrophil to lymphocyte ratio and albumin. Multivariate cox regression and logistic regression models were used to measure hazard ratios (HR) and odds ratios (OR) for overall survival (OS), progression-free survival (PFS) and observed response rate (ORR). Results: Among 152 mUC ICI-treated pts, 107 had NGS data (FoundationOne, UCSF500, Strata), including 85 with TMB data. For the 107 pts with NGS, median age was 70 yrs, majority were male (69, 64%), Caucasian (70, 65%), had pure urothelial histology (57, 53%), and had first-line ICI (55, 51%). ORR was 35%, median PFS was 3.9 mos (95% CI: 2.6-7.5 mos), and median OS was 17.4 mos (95% CI: 14.1-30.6 mos). Biomarkers associated with improved outcomes to ICI, independent of relevant clinical factors, included alterations in ARID1A and DDR, as well as high TMB (>10 Mut/Mb). Inferior outcomes were seen in pts with CDKN2B, KDM6A, FGF3, FGF4, and FGF19 alterations (Table). Conclusions: In this large retrospective multivariate analysis controlling for clinical factors in ICI-treated mUC pts, we found multiple biomarkers associated with improved or inferior outcomes. These hypothesis-generating findings can inform clinical decision making and trial design for mUC pts treated with ICIs, and should be validated in larger cohorts. [Table: see text]

Association of biomarkers and response to immune checkpoint inhibitors (ICIs) in patients with metastatic urothelial carcinoma (mUC) with high and low tumor mutation burden (TMB)

534

Background: ICIs are frequently used as therapy in mUC, but only a minority of patients (pts) respond to treatment. High TMB is associated with improved outcomes to ICIs. However, much is unknown about biomarkers associated with ICI outcomes in pts with high and low TMB respectively. Methods: We retrospectively identified mUC pts with known TMB status and available next generation sequencing (NGS) results treated with ICI monotherapy at our institution. TMB high was defined as ≥ 10 mutations/Mb, with the rest being TMB low. Somatic alterations present in ≥10% pts ( ARID1A, CCND1, CDKN2A, CDKN2B, ERBB2, FGF3, FGF4, FGF19, FGFR3, KDM6A, MDM2, MLL2, PIK3CA, RB1, TERTp, TP53, TSC1), and presence of DNA damage response (DDR) alterations were assessed as biomarkers of interest. Within the TMB-high and TMB-low pt groups we separately assessed patients based on the presence or absence of these somatic alterations, APOBEC mutational signature and high PD-L1 expression. Log rank test was used to determine differences in overall survival (OS) and progression free survival (PFS) among these groups. P-value ≤0.05 was considered significant. Results: Among 107 mUC pts treated with ICI monotherapy between 12/2014 and 3/2022 who had NGS data (UCSF500, FoundationOne, Strata), 85 pts had TMB data, including 47 TMB high pts and 38 TMB low pts. Among 85 pts with known TMB status, median age was 76 yrs, the majority were male (55, 65%), Caucasian (57, 67%), had pure urothelial histology (46, 55%) and were treated with ICIs in frontline setting (47, 55%). Median OS was 17.2 mos and median PFS was 3.42 mos. In TMB high pts, presence of DDR , MLL2, KDM6A, PIK3CA and TERTp alterations were each associated with improved outcomes, while presence of CDKN2B alterations was associated with inferior outcomes (Table). Among TMB low pts, those with RB1 alterations had shorter mOS (11.3 months vs 17.2 months; p=0.04) compared to wild-type pts. Conclusions: In this single-center retrospective analysis of mUC pts, we identified somatic alterations that were predictive of outcomes with ICI treatment in TMB high and TMB low pts respectively. Further exploration of biomarkers in patients stratified by TMB status is warranted in larger cohorts. [Table: see text]

PSMA PET Scan

This JAMA Oncology Patient Page describes the PSMA PET scan, an imaging test used to detect prostate cancer throughout the body.

Association of the Time to Immune Checkpoint Inhibitor (ICI) Initiation and Outcomes With Second Line ICI in Patients With Advanced Urothelial Carcinoma

BACKGROUND

Early progression on first-line (1L) platinum-based therapy or between therapy lines may be a surrogate of more aggressive disease and poor outcomes in advanced urothelial carcinoma (aUC), but its prognostic role regarding immune checkpoint inhibitor (ICI) response and survival is unclear. We hypothesized that shorter time until start of second-line (2L) ICI would be associated with worse outcomes in aUC.

PATIENTS AND METHODS

We performed a retrospective multi-institution cohort study in patients with aUC treated with 1L platinum-based chemotherapy, who received 2L ICI. Patients receiving switch maintenance ICI were excluded. We defined time to 2L ICI therapy as the time between the start of 1L platinum-based chemotherapy to the start of 2L ICI and categorized patients a priori into 1 of 3 groups: less than 3 months versus 3-6 months versus more than 6 months. We calculated overall response rate (ORR) with 2L ICI, progression-free survival (PFS) and overall survival (OS) from the start of 2L ICI. ORR was compared among the 3 groups using multivariable logistic regression, and PFS, OS using cox regression. Multivariable models were adjusted for known prognostic factors.

RESULTS

We included 215, 215, and 219 patients in the ORR, PFS, and OS analyses, respectively, after exclusions. ORR difference did not reach statistical significance between patients with less than 3 months versus 3-6 months versus more than 6 months to 2L ICI. However, PFS (HR 1.64; 95% CI 1.02-2.63) and OS (HR 1.77; 95% CI 1.10-2.84) was shorter among those with time to 2L ICI less than 3 months compared to those who initiated 2L ICI more than 6 months.

CONCLUSION

Among patients with aUC treated with 2L ICI, time to 2L ICI less than 3 months was associated with lower, but not significantly different ORR, but shorter PFS and OS compared to 2L ICI more than 6 months. This highlights potential cross resistance mechanisms between ICI and platinum-based chemotherapy.

Association Between Sites of Metastasis and Outcomes With Immune Checkpoint Inhibitors in Advanced Urothelial Carcinoma

BACKGROUND

Sites of metastasis have prognostic significance in advanced urothelial carcinoma (aUC), but more information is needed regarding outcomes based on metastatic sites in patients treated with immune checkpoint inhibitors (ICI). We hypothesized that presence of liver/bone metastases would be associated with worse outcomes with ICI.

METHODS

We identified a retrospective cohort of patients with aUC across 26 institutions, collecting demographics, clinicopathological, treatment, and outcomes information. Outcomes were compared with logistic (observed response rate; ORR) and Cox (progression-free survival; PFS, overall survival; OS) regression between patients with/without metastasis beyond lymph nodes (LN) and those with/without bone/liver/lung metastasis. Analysis was stratified by 1st or 2nd+ line.

RESULTS

We identified 917 ICI-treated patients: in the 1st line, bone/liver metastases were associated with shorter PFS (Hazard ratio; HR: 1.65 and 2.54), OS (HR: 1.60 and 2.35, respectively) and lower ORR (OR: 0.48 and 0.31). In the 2nd+ line, bone/liver metastases were associated with shorter PFS (HR: 1.71 and 1.62), OS (HR: 1.76 and 1.56) and, for bone-only metastases, lower ORR (OR: 0.29). In the 1st line, LN-confined metastasis was associated with longer PFS (HR: 0.53), OS (HR:0.49) and higher ORR (OR: 2.97). In the 2nd+ line, LN-confined metastasis was associated with longer PFS (HR: 0.47), OS (HR: 0.54), and higher ORR (OR: 2.79); all associations were significant.

CONCLUSION

Bone and/or liver metastases were associated with worse, while LN-confined metastases were associated with better outcomes in patients with aUC receiving ICI. These findings in a large population treated outside clinical trials corroborate data from trial subset analyses.

A Phase Ib/II Study of the CDK4/6 Inhibitor Ribociclib in Combination with Docetaxel plus Prednisone in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Ribociclib, a CDK4/6 inhibitor, demonstrates preclinical antitumor activity in combination with taxanes. We evaluated the safety and efficacy of ribociclib plus docetaxel in a phase Ib/II study in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients had chemotherapy-naïve mCRPC with progression on ≥ 1 androgen receptor signaling inhibitor (ARSI). The phase II primary endpoint was 6-month radiographic progression-free survival (rPFS) rate, with an alternative hypothesis of 55% versus 35% historical control. Circulating tumor cells (CTC) were collected at baseline and genomically profiled.

RESULT

Forty-three patients were enrolled (N = 30 in phase II). Two dose-limiting toxicities were observed (grade 4 neutropenia and febrile neutropenia). The recommended phase II dose (RP2D) and schedule was docetaxel 60 mg/m2 every 21 days plus ribociclib 400 mg/day on days 1-4 and 8-15 with filgrastim on days 5-7. At the RP2D, neutropenia was the most common grade ≥ 3 adverse event (37%); however, no cases of febrile neutropenia were observed. The primary endpoint was met; the 6-month rPFS rate was 65.8% [95% confidence interval (CI): 50.6%-85.5%; P = 0.005] and median rPFS was 8.1 months (95% CI, 6.0-10.0 months). Thirty-two percent of evaluable patients achieved a PSA50 response. Nonamplified MYC in baseline CTCs was associated with longer rPFS (P = 0.052).

CONCLUSIONS

The combination of intermittent ribociclib plus every-3-weeks docetaxel demonstrated acceptable toxicity and encouraging efficacy in ARSI-pretreated mCRPC. Genomic profiling of CTCs may enrich for those most likely to derive benefit. Further evaluation in a randomized clinical trial is warranted.

Biomarkers predictive of response to enfortumab vedotin (EV) treatment in advanced urothelial cancer (aUC)

531

Background: EV is an antibody-drug conjugate which recently received full FDA approval for treatment-refractory aUC. Molecular biomarkers and characteristics of patients (pts) most likely to respond to EV therapy have not been well defined. Methods: We retrospectively identified all aUC pts treated with EV at our institution. Clinicopathologic, treatment and response data were abstracted from pt charts. Pts were considered responders to EV if they had a complete response on initial scans after 2-3 months of treatment, or were treated with EV for ≥ 6 months. Responders and non-responders were compared in terms of their molecular and clinical characteristics using Chi-squared test. Most common somatic alterations present in ≥10 pts ( TERTp, TP53, CDKN2A, CDKN2B) were also used to divide pts with available next-generation sequencing (NGS) results into groups with and without these alterations. Log rank test was used to determine differences in overall survival (OS) and progression free survival (PFS) among these groups. Results: Between 1/2020 and 8/2021 a total of 32 pts received EV and 28 had NGS data available with either FoundationOne (14 pts), UCSF500 (13 pts) or Strata (1). Median age was 69.5 years, 24 (75%) were male, 22 (69%) Caucasian, 22 (69%) had pure urothelial histology and 22 (69%) primary tumor location in the bladder. At EV start, 24 (75%) had visceral metastases (mets), 8 (25%) had liver mets, and 13 (41%) had bone mets. Median follow-up from EV start was 12.5 months (range 0.5-36); 20 (63%) pts received EV monotherapy, and 12 (37%) received EV as part of a combination regimen. Non-responders were more likely to have bone metastases (69% vs 21%, p<0.01), but were otherwise similar in baseline clinical characteristics to responders. TP53 alterations were enriched in responders relative to non-responders, whereas non-responders had more CDKN2B alterations (Table). Similar findings were seen in the subset of pts treated with EV monotherapy. Pts with TP53 alterations had longer OS (NR vs 17.0 months, p=0.06) and PFS (NR vs 6.6 months, p=0.04) relative to wild-type pts. Shorter PFS was seen in pts with CDKN2A (4.4 months vs NR, p=0.05) and CDKN2B (4.3 months vs NR, p=0.02) alterations, but no differences in OS were observed. Conclusions: In this retrospective cohort of aUC pts with available NGS data, presence of TP53 and absence of CDKN2A and CDKN2B alterations were associated with favorable responses and improved clinical outcomes with EV, suggesting they may be biomarkers of response to EV. These preliminary findings should be validated in larger cohorts.[Table: see text]

Association of time to second-line (2L) immune-checkpoint inhibitors (ICI) and outcomes with ICIs in patients (pts) with advanced urothelial carcinoma (aUC)

505

Background: Current standard therapy for most pts with aUC is first-line (1L) platinum-based chemotherapy followed by ICI maintenance (or 2L if progression). Shorter time on 1L or between therapy lines may be a surrogate of more aggressive disease and poor outcome, but its prognostic role in ICI response is unclear. We hypothesized that shorter time until start of 2L ICI would be associated with worse outcomes in aUC. Methods: We performed a retrospective multi-institution cohort study in pts with aUC treated with 1L platinum-based chemotherapy, who later received 2L ICI. Pts receiving maintenance ICI were excluded. We calculated the time from start of 1L platinum chemotherapy to start of 2L ICI, dichotomizing the exposure into ≤6 months and >6 months. We compared overall response rate (ORR) to 2L ICI, progression-free survival (PFS) and overall survival (OS) from the start of 2L ICI between the two populations. ORR was compared among groups using multivariable logistic regression and PFS, OS using cox regression. Analysis was adjusted for calculated Bellmunt score. Results: From a total of 1283 pts, 462 received 1L platinum chemotherapy; among those, 350 received 2L ICI. After exclusions, 270, 269 and 260 pts were included in the ORR, PFS and OS analyses, respectively. Median age was 70 years, 78% men, 75% White, 74% with pure urothelial histology, 21% upper tract, 60% received cisplatin in 1L. Pts with time to 2L ICI ≤6 months had significantly higher Bellmunt scores (32% vs 22% score=2, 9% vs 3% score=3). ORR and PFS were comparable between pts with ≤ and >6 months to 2L ICI. However, OS was significantly longer for pts with >6 months to 2L ICI (median [m]OS 13 vs 7 months, p=0.002), (Table). Conclusions: Among pts with aUC treated with 2L ICI, time to 2L ICI ≤6 months from 1L platinum based chemotherapy was associated with similar ORR and PFS but shorter OS. Limitations include retrospective nature, patient selection, confounding factors. More studies are needed on the impact of platinum resistance in pts with aUC treated with ICIs.[Table: see text]

Clinical and molecular features of low prostate-specific membrane antigen (PSMA) expression in patients (pts) with metastatic castration resistant prostate cancer (mCRPC)

167

Background: Low PSMA uptake on positron-emission tomography is seen in up to 30% of mCRPC pts and represents a clinically distinct subgroup with adverse outcomes. We assessed transcriptional and clinical features associated with low PSMA ( FOLH1) gene expression in mCRPC. Methods: A retrospective analysis of mCRPC biopsy samples with RNA-seq data was undertaken. Normalized FOLH1 expression was compared across histologic subtypes and sites of disease. We assessed the association between FOLH1 expression, selected androgen receptor (AR) target genes, master regulators of neuroendocrine differentiation, and previously validated AR activity and treatment-associated small cell neuroendocrine carcinoma (t-SCNC) transcriptional signature scores using Pearson correlations. Associations between FOLH1 and both PSA50 response to subsequent AR-targeted therapy and overall survival (OS) were examined by logistic regression and Cox proportional hazard models, respectively. Results: Samples from 97 pts were identified, of which 18% harbored t-SCNC histology. 45% of pts had visceral metastases at the time of biopsy, and 41% received subsequent AR-targeted therapy. Median FOLH1 expression was lower in pts with visceral metastases vs no visceral metastases (14.7 vs 15.6, p = 0.02) but was not significantly different across t-SCNC vs adenocarcinoma biopsies (14.3 vs 15.4, p = 0.13). FOLH1 expression was positively correlated with AR transcriptional activity and AR target genes, and negatively correlated with master regulators of neuroendocrine differentiation and t-SCNC transcriptional signature scores (Table). Low FOLH1 expression did not predict PSA50 response to subsequent AR-targeted therapy (OR 0.97, p = 0.8), but was associated with shorter OS on univariate analysis (HR 1.09, 95% CI 1.02-1.16, p=0.01). A post-hoc analysis revealed a trend towards decreased median OS in pts with FOLH1 expression <12 (7.5 vs 17.1 months, log-rank p = 0.06). Conclusions: In this retrospective analysis of mCRPC pts, low FOLH1 expression was associated with transcriptional features of t-SCNC, decreased AR activity, and shorter OS. These findings are hypothesis-generating and prospective validation is needed.[Table: see text]

Serial stereotactic body radiation therapy for oligometastatic prostate cancer (PCa) detected by positron emission tomography (PET) imaging

109

Background: Radiopharmaceuticals, including Ga-68-prostate specific membrane antigen (PSMA)-11, F-18-fluciclovine, and choline C-11, are increasingly used to stage and inform therapies for PCa. Stereotactic body radiation therapy (SBRT) to PET-detected oligometastatic PCa has been shown to improve progression free survival (PFS) compared to observation. However, for men who subsequently develop oligorecurrent disease, outcomes following second SBRT are unknown. Methods: A retrospective, single-center, cohort study was conducted. Pts were identified through electronic health records. Inclusion criteria included pts with oligometastatic (1-5 lesions) PCa detected on PSMA, fluciclovine, or choline C-11 PET who underwent 2 consecutive courses of SBRT to tracer-avid oligometastatic disease between 7/2013 and 7/2021. Exclusion criteria included presence of visceral metastases and pure small cell neuroendocrine PCa. Data on stage, tracer type, concurrent systemic therapy, and prostate-specific antigen (PSA) responses for first SBRT (SBRT1) and second SBRT (SBRT2) were collected. Outcomes included PSA decline of ≥50% (PSA50), ≥90% (PSA90), and PSA-PFS. SBRT2 outcomes were compared based on change of concurrent systemic therapy with SBRT2 (e.g., addition of abiraterone or anti-androgen withdrawal) and PSA50 to SBRT1 using Fisher’s exact text and Wilcoxon rank sum test, respectively. Results: A total of 12 pts met eligibility criteria. At SBRT1, 10 (83%) pts had hormone-sensitive PCa (HSPC) and 2 (17%) had castration-resistant PCa (CRPC). For PET tracers, 7 (58%) used PSMA, 4 (33%) fluciclovine, and 1 (8%) choline. After SBRT1, 12 pts (100%) had a PSA decline, 8 (67%) had a PSA50 response, and 6 (50%) a PSA90 response. Median PSA PFS after SBRT1 was 30mo (95%CI 9-65mo). Six (50%) SBRT1 pts had a concurrent change in systemic therapy. At SBRT2, 8 (67%) pts had HSPC and 4 (33%) had CRPC; 7 (58%) used PSMA and 5 (42%) fluciclovine. After SBRT2, 12 (100%) pts had a PSA decline, 8 (67%) had a PSA50 response, and 8 (67%) a PSA90 response. After SBRT2, median PSA PFS was 23mo (95%CI 12-35mo). Among 7 pts who had a concurrent change in systemic therapy with SBRT2, all (100%) had a PSA50 response; among 5 who did not (4 of whom did not receive any systemic therapy), 1 (20%) had a PSA50 response (P=0.01). Among 8 pts who had a PSA50 response to SBRT1, 7 (88%) had one to SBRT2; among 4 who did not have a PSA50 response to SBRT1, 1 (25%) had one to SBRT2 (P=0.01). No complications related to SBRT were documented. Conclusions: Serial SBRT for oligometastatic PCa detected on fluciclovine, PSMA, or choline PET is feasible and can achieve PSA declines independent of systemic therapy. PSA responses were greater when systemic therapy was changed. This preliminary evidence of benefit, based on PSA responses and PSA PFS, provides rationale for larger, prospective studies of serial SBRT for oligometastatic PCa.

Prostate-specific membrane antigen (PSMA)-based imaging in localized and advanced prostate cancer: a narrative review

Combined molecular and morphologic imaging modalities have emerged in recent years as an alternative to conventional imaging in prostate cancer (PC). In particular, novel prostate-specific membrane antigen (PSMA) radiotracers have demonstrated increased sensitivity and specificity for the initial staging of men with clinically localized PC, as well as for PC detection in the setting of biochemical recurrence (BCR). Molecular imaging is increasingly used to guide treatment decisions in these patients—though its impact on survival has yet to be established. Improved PC detection in men with BCR has also helped to identify a subset of patients with oligometastatic disease. The optimal management of oligometastatic PC and the role of metastasis-directed therapies (MDT) are the subjects of ongoing studies. In comparison to clinically localized or biochemically recurrent PC, the role of molecular imaging in men with advanced disease is less established. In metastatic castration-resistant PC (mCRPC), PSMA-based imaging has primarily been investigated as a companion diagnostic tool to predict and monitor response to PSMA-targeted radioligand therapy (RLT). More recent efforts have focused on using molecular imaging to monitor treatment response to conventional chemohormonal therapies. However, despite promising early results, several barriers remain to the widespread use of PSMA-based imaging in metastatic PC: temporary flares in PSMA uptake have been described in a subset of patients after initiation of therapy, and the underlying mechanism and clinical implications of this phenomenon are still poorly understood. Furthermore, whereas PSMA is invariably expressed in hormone-sensitive PC, loss of PSMA expression is increasingly recognized in a subset of mCRPC patients with aggressive disease. Although this may limit the use of PSMA-based imaging as a standalone modality in advanced PC, loss of PSMA uptake may also provide non-invasive and clinically relevant molecular insight on patients’ underlying tumor biology.

A phase (Ph) 1b/2 study of ribociclib (R) in combination with docetaxel (D) plus prednisone (P) in metastatic castration-resistant prostate cancer (mCRPC)

5043

Background: The survival benefit of D in mCRPC is modest. CDK4/6 inhibitors such as R have shown synergistic activity with taxanes in pre-clinical cancer models. We sought to determine the safety and efficacy of R + D + P in mCRPC patients (pts). Methods: This was a Ph 1b/2 multicenter, open-label single arm trial of mCRPC pts with progression (PD) on ≥ 1 prior androgen receptor signaling inhibitor (ARSi) who had not previously received D for mCRPC (NCT02494921). Pts were treated with escalating doses of R in combination with D + P for 6-9 cycles, followed by single agent maintenance R until radiographic or clinical PD. The Ph 2 primary endpoint was 6-month (mo) radiographic progression-free survival (rPFS) rate by PCWG2 criteria, with a target rate of 55% and null hypothesis of 35%. Ph 2 pts underwent baseline circulating tumor cell (CTC) enumeration and genome sequencing (Epic Sciences). Cox proportional hazard model and log-rank test were used to test for associations between rPFS and CTC burden and copy number (CN) variants, respectively. Results: 43 pts were enrolled from 11/2015 to 6/2019. Median age was 68 (range 55-84). 20.9% of pts had visceral metastases. 33 (77%) had PD on prior abiraterone, 27 (63%) on enzalutamide, and 17 (40%) on both. In Ph 1b, 19 pts were enrolled. In the first cohort (D 75 mg/m2 day [d] 1, R 200 mg/d d2-14 of every 21d cycle), 2 pts experienced DLTs (febrile neutropenia [FN] and grade 4 neutropenia). With an alternative dosing schema of D 60 mg/m2 on d1, and R daily on d1-4 and 8-15 of cycle, with daily G-CSF support on d5-7, the MTD was not reached and D 60 mg/m2 + R 400 mg/d was chosen as the recommended Ph 2 dose (RP2D). In total, 30 pts were treated at RP2D; median number of D cycles was 8.5 and 60% went on to receive maintenance R. The Ph 2 primary endpoint was met with a 6-mo rPFS rate of 65% (95% CI 50-85%). Median rPFS was 8.0 mos (95% CI 4.1-10.0). PSA response rate (RR) defined as ≥50% reduction was 27.6% (95% CI 12.7-47.2%) and objective RR was 30.8% (95% CI 9.1-61.4%). Among pts treated at RP2D, the most common grade ≥3 treatment-related adverse events were neutropenia (n= 11, 36.7%), lymphocytopenia (n=3, 10%); no cases of FN were observed. Baseline CTC burden was associated with an increased risk of radiographic PD or death (HR 1.038, 95% CI 1.001-1.074, p = 0.038). Pts harboring CTCs without MYC (4/11 pts) or CDK6 CN gain (7/11 pts) had prolonged rPFS compared to those with gene amplification (median rPFS 10.76 vs 4.11 mos, p = 0.03, and 7.01 vs 1.92 mos, p = 0.053, respectively). Conclusions: The combination of R + D was well tolerated and showed promising activity in mCRPC pts who had progressed on an ARSi. The Ph 2 study met its primary endpoint, with an encouraging 6-mo rPFS rate of 65%. Lack of MYC or CDK6 amplification on CTC sequencing was associated with longer rPFS. Funding: Novartis Pharmaceuticals, PCF YIA. Managed by the PCCTC. Clinical trial information: NCT02494921.

Immunogenic priming with 177Lu-PSMA-617 plus pembrolizumab in metastatic castration resistant prostate cancer (mCRPC): A phase 1b study

5053

Background: Immune checkpoint inhibitors have limited single agent activity in microsatellite-stable mCRPC. 177Lu-PSMA-617 (Lu) is a PSMA-targeting radioligand therapy that has demonstrated promising anti-tumor activity. We sought to determine whether a single dose of Lu can induce an immunogenic priming effect to improve outcomes of men with mCRPC subsequently treated with pembrolizumab (P). Methods: We undertook a phase 1b, single arm trial enrolling chemotherapy-naïve mCRPC patients (pts) with progression (PD) on at least one prior androgen signaling inhibitor (NCT03805594). Pts were required to have ≥ 3 PSMA-avid lesions on 68Ga-PSMA-11 PET and measurable disease by RECIST 1.1 criteria. No genomic selection was undertaken. Pts were enrolled sequentially on one of three schedules: A) Single dose of Lu (7.4 GBq) followed by initiation of P (200 mg IV q 3 weeks) 28 days later; B) Lu x 1 dose given concomitantly with first P administration; C) Lu x 1 dose given on C2D1 following initiation of P on C1D1. Pts were treated with P until confirmed radiographic or clinical PD. The primary endpoint was safety; key secondary endpoints included PSA response, objective response rate by RECIST 1.1 criteria (ORR), median duration of response (DOR), and radiographic progression-free survival (rPFS). Results: 18 pts were enrolled, 6 per schedule. The median age was 64 (range 51 – 80) and 44% of pts had visceral metastases. The median baseline number of PSMA-avid metastatic lesions was 20 (range 6 – 50+). Six pts (33%) had progressed on prior abiraterone, 4 (22%) on enzalutamide, and 8 (44%) on both. There were no dose-limiting toxicities and one Grade ≥ 3 treatment-related adverse event (AE) (inflammatory arthritis, schedule B). There were no grade ≥ 3 hematologic AEs. The ORR was 8/18 (44%) and median DOR has not been reached (range 1.9+ – 15.9+ months). Four pts (2 on schedule A, 1 on schedule B, 1 on schedule C) with durable partial responses remain on study treatment for 5.4+, 8.9+, 9.2+, and 17.8+ months, respectively. The median rPFS was 6.5 months (95% CI: 2.5 – 9.8). PSA30, PSA50, and PSA90 response rates were 44%, 28%, and 17%, respectively. Fourteen pts (78%), including all durable responders, had somatic genomic data available. One (7%) harbored a DNA repair mutation ( BRCA1, non-responder), none were MSI-high, and all carried low tumor mutational burden (≤ 5 mutations/MB). Single cell sequencing of the immune microenvironment from paired metastatic tumor biopsies is underway. Conclusions: 177Lu-PSMA-617 as a priming dose followed by pembrolizumab was well tolerated and leads to durable responses in a subset of mCRPC without high mutational burden or microsatellite instability, suggesting a possible immunogenic priming effect of radioligand therapy. Further evaluation of the combination is ongoing in a phase 2 study. Clinical trial information: NCT03805594.

Outcomes of patients (pts) with advanced urothelial carcinoma (aUC) treated with immune checkpoint inhibitors (ICIs): Associations with age, race, sex and smoking history

e16526

Background: ICIs have altered the therapeutic landscape in pts with aUC and new biomarkers are needed to better predict response and outcomes with ICIs. It is unclear whether demographics, such as race, age, sex and history of smoking, are associated with outcomes with ICIs. We hypothesized that specific demographic groups (sex, age, race, smoking history) would be associated with outcomes with ICIs in aUC. Methods: We performed a retrospective cohort study across 25 institutions. Data collected included demographic and clinicopathologic factors, response and outcomes. We calculated observed response rate (ORR), Progression-Free Survival (PFS) and overall survival (OS) for specific demographic groups. We built multivariable models (logistic regression for ORR; Cox regression for PFS and OS) with all demographic groups to assess outcomes. Analysis was done for the overall population and stratified by treatment line (first line [1L]; salvage [2+L]). The stratified analysis was also adjusted for known prognostic risk scores (internally developed for 1L; Bellmunt for 2+L); p-value < 0.05 was significant. Results: We identified 1026 pts; 754, 744 and 780 were included in OS, ORR and PFS analysis. Overall, median age at ICI initiation was 70; 26% female; 75% White, 11% Hispanic, 5% Black, 8% other; 69% had smoking history; 28% with mixed histology; 17% with upper tract UC. In the unstratified analysis, age 65-74 (vs < 65) was significantly associated with higher ORR (32% vs 22%) and median PFS (5 vs 3 mo HR 0.8); otherwise no significant difference was noted among groups for ORR, PFS, OS in both the stratified and unstratified analyses (Table). Conclusions: We did not identify significant associations between age, sex, race or smoking history and ORR, PFS, OS with ICIs in pts with aUC. Limitations include retrospective nature, lack of randomization, possible selection and confounding factors. Further research is required to identify prognostic and predictive biomarkers for ICI therapy in aUC.[Table: see text]

TERT promoter mutations and other prognostic factors in patients with advanced urothelial carcinoma treated with an immune checkpoint inhibitor

BACKGROUND

Immune checkpoint inhibitors (ICI) can achieve durable responses in a subset of patients with locally advanced or metastatic urothelial carcinoma (aUC). The use of tumor genomic profiling in clinical practice may help suggest biomarkers to identify patients most likely to benefit from ICI.

METHODS

We undertook a retrospective analysis of patients treated with an ICI for aUC at a large academic medical center. Patient clinical and histopathological variables were collected. Responses to treatment were assessed for all patients with at least one post-baseline scan or clear evidence of clinical progression following treatment start. Genomic profiling information was also collected for patients when available. Associations between patient clinical/genomic characteristics and objective response were assessed by logistic regression; associations between the characteristics and progression-free survival (PFS) and overall survival (OS) were examined by Cox regression. Multivariable analyses were performed to identify independent prognostic factors.

RESULTS

We identified 119 aUC patients treated with an ICI from December 2014 to January 2020. Genomic profiling was available for 78 patients. Overall response rate to ICI was 29%, and median OS (mOS) was 13.4 months. Favorable performance status at the start of therapy was associated with improved OS (HR 0.46, p=0.025) after accounting for other covariates. Similarly, the presence of a TERT promoter mutation was an independent predictor of improved PFS (HR 0.38, p=0.012) and OS (HR 0.32, p=0.037) among patients who had genomic profiling available. Patients with both a favorable performance status and a TERT promoter mutation had a particularly good prognosis with mOS of 21.1 months as compared with 7.5 months in all other patients (p=0.03).

CONCLUSIONS

The presence of a TERT promoter mutation was an independent predictor of improved OS in a cohort of aUC patients treated with an ICI who had genomic data available. Most of the clinical and laboratory variables previously shown to be prognostic in aUC patients treated with chemotherapy did not have prognostic value among patients treated with an ICI. Genomic profiling may provide important prognostic information and affect clinical decision making in this patient population. Validation of these findings in prospective patient cohorts is needed.

Feasibility study of gallium-68 citrate PET as a bone-tropic imaging biomarker in mCRPC

31

Background: Transferrin receptor (TFRC) expression is controlled by the PI3K and MYC signaling pathways, which are frequently dysregulated in prostate cancer (PC). Gallium-68 citrate (68Ga-citrate) is an iron biomimetic, which can be used to image PC in a TFRC dependent fashion. We performed a single-center pilot imaging study to investigate the use of 68Ga-citrate PET in patients with metastatic castration-resistant PC (mCRPC). Methods: Following written informed consent, mCRPC patients were prospectively enrolled and underwent 68Ga-citrate PET imaging. Optional metastatic tumor biopsies were undertaken at the time of imaging. Results: 34 mCRPC patients underwent 68Ga-citrate PET imaging. The median age was 67.5 years old. Median duration of castration resistance was 17.5 months; 14.7% of patients were post-docetaxel. Median serum PSA was 35.2 ng/dL. A total of 483 lesions were detected on conventional imaging (CT, 99mTc-HDP) or 68Ga-citrate PET, including 420 osseous and 63 soft tissue (nodal and visceral) lesions (Table). 67.3% of all lesions were detected on 68Ga-citrate PET, including 74.5% of all osseous lesions but only 19.0% of all soft tissue lesions (p<0.0001). Eight (1.7%) lesions were detected on 68Ga-citrate PET imaging only. Per-lesion average SUVmax (SUVmax,avg) was 6.7. Metastatic biopsies of PET avid lesions were performed in 20 patients (59%); adenocarcinoma histology was confirmed in 14 (70%) cases, treatment-emergent small cell neuroendocrine cancer (t-SCNC) in 6 (30%). There was no significant difference in SUVmax,avg between patients with adenocarcinoma or t-SCNC (SUVmax,avg 7.3 vs 7.6, respectively; Table). Serial 68Ga-citrate PET perfomed in a patient with biopsy-confirmed t-SCNC after 2 cycles of carboplatin/cabazitaxel demonstrated an early metabolic response (28.5% decrease in average SUVmax) confirmed on subsequent conventional imaging. Conclusions: 68Ga-citrate PET detects mCRPC bone metastases in patients with biopsy-proven prostatic adenocarcinoma or t-SCNC, distinguishing it from lineage dependent agents such as PSMA tracers. Detection of an early metabolic response in the bone of a treated t-SCNC patient was observed. Further prospective studies are ongoing coupling serial Ga-citrate PET with investigational agents targeting the MYC signaling pathway. Clinical trial information: NCT02391025. [Table: see text]

Association between prior radical surgery (RS) and outcomes with immune checkpoint inhibitor (ICI) therapy for advanced urothelial carcinoma (aUC)

444

Background: It is unclear whether prior RS of primary tumor is associated with response and outcomes with ICI in aUC. We hypothesized that such response and outcomes would not differ based on prior RS. Methods: We performed a retrospective cohort study including patients (pts) with aUC who received ICI. We compared overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) between pts with vs without RS [cystectomy or (nephro)-ureterectomy]. Analysis was stratified based on ICI therapy line (first-line vs salvage). A separate comparison between pts with prior RS or radiation (RT) only or none was also pursued. ORR was compared between groups using logistic regression, as well OS and PFS using cox regression analysis; a multivariable model was built adjusting for calculated Bellmunt score. P<0.05 was significant. Results: We identified 984 pts from 24 institutions; 682, 704 and 673 were included in OS, PFS and ORR analyses, respectively; 54% of pts had prior RS with median age 68 at ICI initiation with RS vs 71 without RS with similar proportion of men (73-74%) and ever smokers (70-71%). The RS group had higher proportion (%) of white pts (77% vs 71%), lower % of pts with Hb<10g/dL at ICI initiation (23% vs 32%) but not significantly higher % of liver metastasis at ICI initiation (23% vs 17%). Bellmunt score with vs without RS was 16% vs 11%, 50% vs 48%, 27% vs 37%, 7% vs 4% for 0, 1, 2, and 3, respectively. ORR and PFS were not significantly different between groups, while prior RS was associated with longer OS (unadjusted HR 0.8, p=0.03). However, after adjustment for Bellmunt score, this association was not significant (table). Upon stratification based on treatment line, OS was longer with prior RS (0.7, p=0.03) for those treated with salvage ICI but this was not significant after adjusting for Bellmunt score. ORR, PFS and OS were not significantly different between pts receiving prior RT only vs RS vs none. Conclusions: Prior RS was not significantly associated with longer OS in pts with aUC receiving ICI after adjusting for Bellmunt score. Further work is needed to interrogate tumor-host immune interactions and identify biomarkers that can be prognostic and/or predictive of ICI response. [Table: see text]

TERT promoter mutation as a prognostic marker in patients with advanced urothelial carcinoma treated with immune checkpoint inhibitors

476

Background: Reliable predictive markers are lacking in patients (pts) with locally advanced or metastatic urothelial carcinoma (aUC) treated with immune checkpoint inhibitors (ICI). We sought to determine whether specific genomic alterations could be used to predict overall survival (OS) in this patient population. Methods: We undertook a retrospective cohort study of pts with aUC who received ICI and underwent genomic profiling by next-generation sequencing (NGS). All patients underwent NGS using commercially available platforms (e.g. Foundation Medicine, Strata, Invitae), or testing on the CLIA-certified institutional panel UCSF500. Associations between the 20 most frequently altered genes and OS were first examined by Cox regression. Genes with a p <0.1 on univariate analysis and relevant clinical variables were then included in a multivariable analysis. Results: We identified 78 pts treated with ICI for aUC with available genomic profiling results. Median age at ICI initiation was 71; the majority of patients had visceral metastases (70.5%), ECOG performance status ≤1 (62.8%) and received ICI in the post-platinum setting (52.6%). Objective response rate in this cohort was 35.9%, median progression free survival was 4.0 months (95% CI 2.6-10.5) and median OS was 17.5 months (95% CI 14.1-NR) from ICI start. The most commonly altered genes were the TERT promoter (TERTp) (61%), TP53 (52%), RB1 (31%), CDKN2A(29%) and CDKN2B (27%). On univariable analysis there was a trend towards longer OS in pts with TERTp mutations (HR 0.53, 95% CI 0.27-1.06, p = 0.07), and shorter OS in pts with CDKN2B mutations (HR 1.91, 95% CI 0.98-3.73, p = 0.06). Both mutations were included in a multivariable analysis. After adjusting for known prognostic variables (ECOG PS, visceral metastases, albumin, hemoglobin, body mass index [BMI], neutrophil to lymphocyte ratio [NLR], and histology), the presence of a TERTp mutation was significantly associated with improved OS (HR 0.30, 95% CI 0.10-0.93, p = 0.04; Table). Conclusions: The presence of a TERTp mutation was an independent predictor of improved OS in a cohort of aUC pts treated with ICI. Other common mutations and clinical variables were not associated with OS on a multivariable analysis. These findings are hypothesis-generating and prospective validation is needed. [Table: see text]

Periprocedural Bridging in Patients with Venous Thromboembolism: A Systematic Review

BACKGROUND

Vitamin K antagonists (VKA) are the most widely used anticoagulants, and bridging is commonly administered during periprocedural VKA interruption. Given the unclear benefits and risks of periprocedural bridging in patients with previous venous thromboembolism, we aimed to assess recurrent venous thromboembolism and bleeding outcomes with and without bridging in this population.

METHODS

We performed a systematic review searching the PubMed and Embase databases from inception to December 7, 2017 for randomized and nonrandomized studies that included adults with previous venous thromboembolism requiring VKA interruption to undergo an elective procedure, and that reported venous thromboembolism or bleeding outcomes. Quality of evidence was graded by consensus.

RESULTS

We included 28 cohort studies (20 being single-arm cohorts) with, overall, 6915 procedures for analysis. In 27 studies reporting perioperative venous thromboembolism outcomes, the pooled incidence of recurrent venous thromboembolism with bridging was 0.7% (95% confidence interval [CI], 0.4%-1.2%) and 0.5% (95% CI, 0.3%-0.8%) without bridging. Eighteen studies reported major or nonmajor bleeding outcomes. The pooled incidence of any bleeding was 3.9% (95% CI, 2.0%-7.4%) with bridging and 0.4% (95% CI, 0.1%-1.7%) without bridging. In bridged patients at high thromboembolic risk, the pooled incidence for venous thromboembolism was 0.8% (95% CI, 0.3%-2.5%) and 7.5% (95% CI, 3.1%-17.4%) for any bleeding. Quality of available evidence was very low, primarily due to a high risk of bias of included studies.

CONCLUSIONS

Periprocedural bridging increases the risk of bleeding compared with VKA interruption without bridging, without a significant difference in periprocedural venous thromboembolism rates.