Salivary toxicity from PSMA-targeted radiopharmaceuticals: What we have learned and where we are going

Clinical trials of prostate-specific membrane antigen (PSMA) targeted radiopharmaceuticals have shown encouraging results. Some agents, like lutetium-177 [177Lu]Lu-PSMA-617 ([177Lu]Lu-PSMA-617), are already approved for late line treatment of metastatic castration-resistant prostate cancer (mCRPC). Projections are for continued growth of this treatment modality; [177Lu]Lu-PSMA-617 is being studied both in earlier stages of disease and in combination with other anti-cancer therapies. Further, the drug development pipeline is deep with variations of PSMA-targeting radionuclides, including higher energy alpha particles conjugated to PSMA-honing vectors. It is safe to assume that an increasing number of patients will be exposed to PSMA-targeted radiopharmaceuticals during the course of their cancer treatment. In this setting, it is important to better understand and mitigate the most commonly encountered toxicities. One particularly vexing side effect is xerostomia. In this review, we discuss the scope of the problem, inventories to better characterize and monitor this troublesome side effect, and approaches to preserve salivary function and effectively palliate symptoms. This article aims to serve as a useful reference for prescribers of PSMA-targeted radiopharmaceuticals, while also commenting on areas of missing data and opportunities for future research.

Early PSA decline after starting second-generation hormone therapy in the post-docetaxel setting predicts cancer-specific survival in metastatic castrate-resistant prostate cancer

BACKGROUND

The objective of this study was to evaluate the prognostic value of early PSA decline following initiation of second-generation hormone therapy (2nd HT), namely abiraterone acetate or enzalutamide, in patients with taxane-refractory metastatic castrate-resistant prostate cancer (mCRPC) and evaluate utility of this metric in informing intensified surveillance/imaging protocols.

METHODS

We retrospectively identified 75 mCRPC patients treated with 2nd HT following docetaxel failure (defined as PSA rise and radiographic progression). Patients were categorized patients into two cohorts based on the first PSA within 3 months after initiation of therapy: PSA reduction ≥50% (Group A) and PSA reduction <50% (Group B). The primary endpoint was cancer-specific mortality (CSM). The secondary endpoint was radiographic disease progression (rDP) on 2nd HT. In univariate and multivariate analyses, we investigated factors associated with rPD and CSM.

RESULTS

We included 75 patients (52 in Group A, 23 in Group B) in the analytic cohort. Baseline clinico-demographic characteristics, including median age, primary Gleason score risk group, median pre-treatment PSA, disease burden, site of metastases, and pre-treatment ECOG score were not statistically different between the two groups. Median follow up time was 30 months and the median time to radiographic disease progression was 28.1 and 12.5 months (p = 0.002) in cohorts A and B, respectively. On univariate and multivariate analyses, both PSA reduction ≥50% and volume of metastatic disease were significantly associated with a decreased risk of radiographic disease progression (HR 0.41, 95% CI 0.21-0.80, p = 0.0113) as well as a decreased risk of cancer-specific mortality (HR 0.29, 95% CI 0.09-0.87, p = 0.0325).

CONCLUSION

PSA reduction ≥50% within 3 months of starting 2nd HT was associated with significantly improved radiographic disease progression-free survival and 3-year cancer-specific mortality. This suggests using PSA 50%-decline metric in surveillance patients with on 2nd HT and identifies patients who require further evaluation with imaging.

Low PSA radiographic disease progression on C11-choline PET

Background

For men with prostate cancer, radiographic progression may occur without a concordant rise in prostate-specific antigen (PSA). Our study aimed to assess the prevalence of radiographic progression using C-11 choline positron emission tomography (PET) imaging in patients achieving ultra-low PSA values and to evaluate clinical outcomes in this patient population.

Methods

In a single institution study, we reviewed the prospectively maintained Mayo Clinic C-11 Choline PET metastatic prostate cancer registry to identify patients experiencing radiographic disease progression (rDP) on C-11 choline PET scan while the PSA value was less than 0.5 ng/mL. Disease progression was confirmed by tissue biopsy or response to subsequent therapy. Clinicopathologic variables were abstracted by trained research personnel. Overall survival was estimated using the Kaplan-Meier method. Intergroup differences were assessed using the log-rank test. A univariate and multivariate Cox regression model was performed to investigate variables associated with poor survival after rDP.

Results

A total of 1323 patients within the registry experienced rDP between 2011 and 2021, including 220 (16.6%) men with rDP occurring at low PSA level. A median (interquartile range [IQR]) of 54.7 (19.7-106.9) months elapsed between the time of prostate cancer diagnosis and low PSA rDP, during which 173 patients (78%) developed castration-resistant prostate cancer (CRPC). Sites of low PSA rDP included local recurrence (n = 17, 8%), lymph node (n = 90, 41%), bone (n = 94, 43%) and visceral metastases (n = 19, 9%). Biopsy at the time of rDP demonstrated small-cell or neuroendocrine features in 21% of patients with available tissue. Over a median (IQR) follow-up of 49.4 (21.3-95.1) months from the time of low PSA rDP, 46% (n = 102) of patients died. Factors associated with poorer survival outcomes include advanced age at rDP, CRPC status, bone and visceral metastasis (p value <0.05). Visceral metastases were associated with decreased overall survival (p = 0.009 by log-rank) as compared with other sites of rDP.

Conclusions

Men with prostate cancer commonly experience metastatic progression at very low or even undetectable PSA levels. Periodic imaging, even at low absolute PSA values, may result in more timely identification of disease progression.

Genomic attributes of prostate cancer across primary and metastatic noncastrate and castrate resistant disease states: a next generation sequencing study of 183 patients

Primary prostatic adenocarcinoma (pPC) undergoes genomic evolution secondary to therapy-related selection pressures as it transitions to metastatic noncastrate (mNC-PC) and castrate resistant (mCR-PC) disease. Next generation sequencing results were evaluated for pPC (n = 97), locally advanced disease (involving urinary bladder/rectum, n = 12), mNC-PC (n = 21), and mCR-PC (n = 54). We identified enrichment of TP53 alterations in high-grade pPC, TP53/RB1 alterations in HGNE disease, and AR alterations in metastatic and castrate resistant disease. Actionable alterations (MSI-H phenotype and HRR genes) were identified in approximately a fifth of all cases. These results help elucidate the landscape of genomic alterations across the clinical spectrum of prostate cancer.

Treatment modalities and survival outcomes in prostate cancer parenchymal brain metastasis

BACKGROUND

Prostate cancer (PCa) parenchymal brain metastases are uncommon and troubling observations in the course of the disease. Our study aims to evaluate the prevalence of brain metastases among PCa patients while reporting various therapeutic modalities, clinical features, and oncological outcomes.

METHODS

We retrospectively identified 34 patients with parenchymal brain metastasis out of 4575 patients using a prospectively maintained database that contains clinicopathologic characteristics of PCa patients between January 2012 and December 2021. Based on the three treatment modalities used, the patients were divided into three groups: stereotactic radiosurgery (SRS), whole brain radiotherapy (WBRT), and systemic therapy alone. The Kaplan-Meier curve was used to calculate overall survival [OS] probability and the Cox proportional hazards regression model was used to compare between groups.

RESULTS

At the time of brain metastasis diagnosis, the median age was 66 years, the median (interquartile range [IQR]) prostate-specific antigen (PSA) was 2.2 (0.1-26.6) ng/ml and the median (IQR) months from initial PCa diagnosis to brain metastasis development was 70.8 (27.6-100.9). The median (IQR) primary Gleason score was 8 (7-9) and over a median (IQR) follow-up time of 2.2 (1.2-16.5) months, 76.5% (n = 26) of the patients died. Thirteen (38.2%) patients had solitary lesion, whereas 21 (61.8%) had ≥2 lesions. The lesions were supratentorial in 19 (55.9%) patients, infratentorial in six (17.6%), and both sides in nine (26.5%). Among all 34 patients, 10 (29.4%) were treated with SRS, seven (20.6%) with WBRT, and 17 (50%) with systemic therapy alone. OS varied greatly between the three treatment modalities (log-rank test, p = 0.049). Those who were treated with SRS and WBRT had better OS compared with patients who were treated with systemic therapy alone (hazard ratio: 0.37, 95% confidence interval: 0.16-0.86, p = 0.022).

CONCLUSIONS

In our single-institutional study, we confirmed that PCa brain metastasis is associated with poor survival outcomes and more advanced metastatic disease. Furthermore, we found that SRS and WBRT for brain metastasis in patients with recurrent PCa appear to be associated with improved OS as compared with systemic therapy alone and are likely secondary to selection bias.

Coping Mechanisms for Financial Toxicity Among Patients With Metastatic Prostate Cancer: A Survey-based Assessment

PURPOSE

Assessments of financial toxicity among patients with metastatic prostate cancer are lacking. Using patient surveys, we sought to identify coping mechanisms and assess characteristics associated with lower financial toxicity.

MATERIALS AND METHODS

Surveys were administered to all patients seen at a single center's Advanced Prostate Cancer Clinic over a 3-month period. Surveys included the COST-FACIT (COmprehensive Score for Financial Toxicity) and coping mechanism questionnaires. Patients with metastatic disease (lymph nodes, bone, visceral) were included for analysis. Coping mechanisms were compared between patients experiencing low (COST-FACIT >24) vs high (COST-FACIT ≤24) financial toxicity using Fisher's exact test. Multivariable linear regression was used to evaluate characteristics associated with lower financial toxicity.

RESULTS

Overall, 281 patients met inclusion criteria of which 79 reported high financial toxicity. In multivariable analysis, characteristics associated with lower financial toxicity included older age (estimate: 0.36, 95%CI: 0.21-0.52), applying for patient assistance programs (estimate: 4.42, 95%CI: 1.72-7.11), and an annual income of at least $100,000 (estimate: 7.81, 95%CI: 0.97, 14.66). Patients with high financial toxicity were more likely to decrease spending on basic goods (35% vs 2.5%, P < .001) and leisure activities (59% vs 15%, P > .001), as well as use savings (62% vs 17%, P < .001) to pay for their treatment.

CONCLUSIONS

In this cross-sectional study, patients with metastatic prostate cancer and high financial toxicity were more likely to decrease spending on basic goods and leisure activities and use savings to pay for care. Understanding the impact of financial toxicity on patients' lives is crucial to inform shared decision-making and interventions designed to mitigate financial toxicity in this population.

Prognostic value of C-11 choline PET/CT scan in patients with metastatic castration resistant prostate cancer (m-CRPC) undergoing treatment with radium-223

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Background: Radium-223 (Ra-223) has been approved for the treatment of metastatic castration resistant prostate cancer (mCRPC) with predominantly osseous metastases. PSA flare phenomenon with Ra-223 limits the use of PSA as a prognostic tool to predict treatment response. Currently, there is a lack of diagnostic tools to predict treatment response to Ra-223. Therefore, we sought to investigate the role of mid-treatment C-11 choline PET/CT scan in predicting overall response to Ra-223. Methods: In a single institute retrospective study, we identified 32 patients who were treated with a full course of 4-6 cycles of Ra-223 and were evaluated with both PSA and C-11 choline PET scan before treatment, at mid-treatment, and after a complete course of Ra-223 between 2013 – 2018. Ra-223 was used as salvage therapy for their predominant bone disease after failing chemotherapy and 2nd generation hormone therapy. Blind repeat radiographic evaluation of patients’ scans was performed by a radiologist specialized in nuclear radiology. Favorable response was defined by achieving partial response or stable disease on imaging, while unfavorable response was defined by showing progressive disease on imaging. Results: Mean age (±SD) at starting Radium223 was 67.6 (±7.1) years, median (IQR) primary Gleason score was 9 (8-9), and median (IQR) pretreatment PSA was 13.5 (5.4-39.6) ng/ml. 78% of the patients (n=25) completed 6 cycles of Ra-223, 15% of the patients (n=5) completed 5 cycles, and 6% (n=2) received only 4 cycles. At mid-treatment scanning, 25% of the patients (n=8) showed favorable response (Group A), while 75% of the patients (n=24) showed unfavorable response (B). After a complete course of treatment, 62.5% of patients (n=5) in Group (A) continued to show favorable response, while only 8.3% of patients (n=2) in Group (B) showed favorable response (p-value= 0.0023). Conclusions: Mid-treatment evaluation with C-11 choline PET/CT scan can predict overall response to Radium 223. Patients with progressive disease at mid-treatment evaluation are very likely not going to respond to further treatment. Further studies and clinical trials are warranted.

Financial toxicity and coping mechanisms in patients with metastatic prostate cancer: A pilot study

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Background: Assessments of financial toxicity among patients with metastatic prostate cancer are lacking. We sought to describe the prevalence and severity of financial toxicity, identify coping mechanisms, and assess characteristics that may be protective of financial toxicity among such patients at our institution. Methods: All patients evaluated in the advanced prostate cancer clinic at Mayo Clinic, Rochester, MN, were approached to complete a survey between February and May 2022. The survey consisted of three parts: 1) demographic, cancer, and treatment characteristics; 2) a coping mechanism questionnaire; and 3) The Comprehensive Score for Financial Toxicity (COST-FACIT) questionnaire. COST-FACIT scores range from 0-44, with lower scores signifying higher financial toxicity. Patients were defined as having either high (COST-FACIT score >24) or low (COST-FACIT score ≤24) financial toxicity. Coping mechanisms were compared between patients with low and high financial toxicity using Fisher’s exact test. Multivariable linear regression was used to evaluate patient characteristics associated with high COST-FACIT scores. Results: Of the 786 patients approached, 417 (53.1%) completed the survey and 281 met inclusion criteria. The median COST-FACIT score was 30 (IQR 24-36). On multivariable analysis, characteristics associated with lower financial toxicity included older age, (estimate:0.36, 95%CI 0.21-0.52), applying for patient assistance programs (estimate:4.42, 95%CI 1.72-7.11), and an annual income of at least $100,000 (estimate:7.81, 95%CI 0.97,14.66). Patients with high financial toxicity were more likely to decrease spending on basic goods (34.6% vs. 2.5%, p<0.001) and leisure activities (61.5% vs. 16.9%, p>0.001), as well as use savings (61.5% vs. 16.9%, p<0.001) to pay for their treatment. However, few patients stopped or partially filled their prostate cancer treatments due to cost. Conclusions: In this cross-sectional study of patients with metastatic prostate cancer, older age, higher income, and applying for patient assistance programs were associated with lower financial toxicity. Greater self-reported financial toxicity was associated with decreased spending on basic goods, leisure activities, and tapping into savings. On rare occasion they delayed or skipped treatment. These findings are important to inform treatment shared decision-making and supportive interventions to mitigate financial toxicity in metastatic prostate cancer.

Survival patterns based on site-specific visceral metastasis in patients with metastatic prostate cancer: Are outcomes of visceral metastases the same?

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Background: Metastatic visceral involvement in prostate cancer patients conveys a poor prognosis. Survival patterns of site-specific visceral metastasis are poorly understood. Here, we sought to investigate survival patterns in prostate cancer patients according to their first detected site of visceral metastasis. Methods: Retrospectively, we identified 200 patients with visceral metastatic prostate cancer. Patients were divided into three groups according to first site detected with visceral metastases; first-site lung metastases, first-site brain metastases, and first-site liver metastases. Visceral metastases were detected on either conventional imaging (CT/MRI), metabolic imaging (C-11 choline), or PSMA PET-CT scan. Follow up duration of our study was 80 months. Results: Clinicopathological variables are shown. The K-M curve of overall survival of the entire cohort suggests better survival patterns in patients with first-site lung metastases compared to patients with first-site brain or liver metastases (p<0.0001). In subset analysis of patients with CRPC, the K-M curve of overall survival, which demonstrates better survival outcomes in patients with first-site lung metastases in comparison with patients with first-site brain or liver metastases (p<0.0001). Conclusions: Our data suggests that prostate cancer patients with visceral metastatic disease have different survival patterns according to the first site detected with visceral metastasis. In our cohort, patients with first-site lung metastasis demonstrated better survival outcomes than patients with first-site brain or liver metastasis. Further studies are warranted. [Table: see text]

High-volume mCRPC is associated with decreased cancer specific survival in patients on second-generation hormone therapy in the post docetaxel setting

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Background: In the setting of disease progression of metastatic castrate resistant prostate cancer (mCRPC) on docetaxel, abiraterone acetate (AA) and enzalutamide are two commonly used second line therapies with data demonstrating survival benefits. Less is known about patient specific factors that contribute to success with these therapies. The objective of this study is to improve patient selection for post-docetaxel second generation hormone therapy (AA or enzalutamide) by evaluating whether overall metastatic burden is associated with treatment response in this setting. Methods: By retrospective chart review, patients with mCRPC treated with AA or enzalutamide following docetaxel failure (defined as PSA rise and radiographic progression) were identified. Patients were categorized into low volume and high volume metastatic disease based on the number of pre-treatment metastatic lesions; where low volume disease describes patients with ≤ 5 metastatic lesions (e.g. oligometastatic disease), and high volume disease represents patients with > 5 individual lesions. The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Median follow-up time was 29.5 months. Results: 75 patients were identified and included in our analysis: 39 with high volume metastatic disease, and 36 with low volume metastatic disease. Baseline characteristics of age and pre-treatment ECOG were not statistically different between these groups. Pre-treatment high-volume disease burden was significantly associated with increased risk of radiographic disease progression (HR 4.21, 95%CI 1.97-8.99, p < 0.0001) and cancer specific mortality (HR 5.84, 95% CI 1.58-21.53, p = 0.0026) during treatment with second generation androgen deprivation therapy. Conclusions: High volume metastatic disease burden is associated with significantly increased cancer specific mortality and decreased progression free survival for patients on second line therapy with AA or enzalutamide following docetaxel treatment failure.

Factors associated with poor survival outcomes in patients with prostate cancer (PCa) with radiographic disease progression in the setting of low PSA

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Background: Recent studies, including a post-hoc analysis of the ARCHES trial, highlight radiographic disease progression (rDP) occurring without concordant rise in prostate specific antigen (PSA). In a previous study by our group, we reported that almost 40% of patients on 2nd generation hormone therapy experience rDP with non-rising PSA and have poor survival outcomes. The current analysis more specifically focuses on the subgroup of patients with rDP occurring at low PSA (<0.5 ng/dL) and describes factors associated with poorer survival outcomes in this patient population. Methods: In a single institution study, we reviewed the prospectively maintained Mayo Clinic C-11 Choline PET registry for patients treated between 2011 and 2021, who experienced rDP at low PSA (value < 0.5 ng/mL). Disease progression on C-11 choline PET was confirmed by either tissue biopsy or subsequent response to therapy. We investigated factors associated with poor cancer-specific survival outcomes in univariable and multivariable cox regression analyses. Results: In total, 220 (16%) patients experiencing rDP at low PSA were identified. Median (IQR) age at rDP was 67.91 (61.10 – 73.87) yrs., median (IQR) primary Gleason score was 9 (7-9), and median (IQR) PSA was 0.17 (0 – 0.32) ng/ml. 75% of the patients (n=166) had CRPC disease status at time of rDP. Prior systemic treatments included 2nd generation HT in 18% (n= 40) and chemotherapy in 31% (n=70). Sites of rDP were divided into 7% local (n=16), 42% lymph nodes (n=91), 43% bone (n=95), and 8% visceral metastases (n=18). Over a median follow-up duration of 55 months, 46% of patients (n=100) reported death. Factors associated with poor survival outcomes are demonstrated in the table and include age at rDP, CRPC status, and disease location (P-value <0.05). Conclusions: We found that radiographic disease progression commonly occurs at low PSA (<0.5 ng/mL). CRPC-disease status and the development of visceral metastases are associated with particularly poor survival outcomes. To identify early progression, monitoring with imaging may be warranted, even in the patients with low PSA. [Table: see text]

Effect of early PSA decline after starting second-generation hormone therapy in the post-docetaxel setting on cancer-specific survival in metastatic castrate-resistant prostate cancer

189

Background: The objective of this study is to evaluate the prognostic value of early PSA decline following initiation of second-generation hormone therapy (2nd HT), namely abiraterone acetate or enzalutamide, in the post-chemotherapy setting in patients with metastatic castrate-resistant prostate cancer (mCRPC). Methods: We retrospectively identified 75 m-CRPC patients treated with 2nd HT following docetaxel failure (defined as PSA rise and radiographic progression). Patients were categorized into two groups based on first PSA within 3 months after initiation of therapy: PSA reduction ≥ 50% (Group A) and PSA reduction < 50% (Group B). The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Results: There were 75 patients (52 in group A, 23 in group B) in the analytic cohort. Baseline clinical and demographic characteristics, including median age, primary Gleason score risk group, median pre-treatment PSA, disease burden, site of metastases, and pre-treatment ECOG score were not statistically different between the two groups. PSA reduction ≥50% was significantly associated with decreased risk of radiographic disease progression (HR 0.41, 95%CI 0.21-0.80, p = 0.0113) as well as decreased risk of cancer-specific mortality (HR 0.29, 95%CI 0.09-0.87, p = 0.0325). Conclusions: PSA reduction ≥50% within 3 months of starting 2nd HT for patients with mCRPC who have failed first-line docetaxel is associated with significantly improved 3-year cancer-specific mortality and progression free survival. Our data supports the use of PSA as an early prognosticating marker for patient outcomes on this second line therapy. [Table: see text]

Characterizing changes in tumor mutational burden (TMB) by serial circulating tumor DNA (ctDNA) testing in patients with advanced prostate cancer (aPC)

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Background: In part, TMB guides therapeutic decisions on the use of immune checkpoint inhibitors (ICIs) in aPC. Most patients (pts) with aPC do not have high TMB (TMB-H) at the time of initial assessment. However, TMB changes over time (from treatment pressure) as pts progress through lines of therapy (LOT) has not been extensively explored in aPC. We describe real world data on changes to blood TMB (bTMB) in pts with aPC exposed to several LOT. Methods: Genomic results from pts with aPC who had ≥1 ctDNA test(s) with TMB analyzed (Guardant360, Guardant Health, Inc) as part of clinical care from Oct 2020 – Jun 2022 were retrospectively queried. Clinical factors were extracted from test requisition forms; pts from Mayo Clinic had additional factors, including intervening treatment, extracted from medical records. High bTMB (TMB-H) was defined as ≥13.4 mut/Mb, as previously reported. Proportions were compared using Fisher’s Exact Test. Results: 316 patients with a median age of 72 (range: 44-91) were analyzed. Initial median TMB for the entire cohort was 8.18 mut/Mb (range: 0.01-268.3). On subsequent test, TMB decreased in 122(40%), increased in 173(55%), of whom 29 (17%) became TMB-H; 21 (7%) had unchanged TMB. Median time between tests was 182 days (range: 21-578). 101 patients with 262 tests and a median age of 71 years (range: 46-87) were clinically annotated in the Mayo cohort of whom 58 had >2 consecutive TMB scores: 25 (43%) had TMB increase, of whom 4 (16%) became TMB-H, 23 (40%) had TMB decrease, 10 (17%) had dynamic changes with increases and decreases. Numeric but not statistically significant differences in clinical factors were observed between groups (p>0.05). Conclusions: In this real world cohort, variation in TMB is seen with increasing LOT. Importantly, nearly 1 in 5 patients with increasing tumor mutational burden develop TMB-H, which may be a clinically actionable finding as these pts become eligible for ICI. Findings underscore the importance of repeat genetic testing with time and LOT. [Table: see text]

Addressing the need for more therapeutic options in neuroendocrine prostate cancer

INTRODUCTION

Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer frequently seen after prolonged treatment of castration resistant prostate cancer (CRPC). NEPC has become increasingly prevalent over the last 20 years, with a poor prognosis caused by a late diagnosis and limited treatment options. Recent advances in PET/CT imaging and targeted radioimmunotherapy are promising, but more research into additional treatment options is needed.

AREAS COVERED

The aim of this review is to analyze the current imaging and treatment options for NEPC, and to highlight future potential treatment strategies. A Pubmed search for 'Neuroendocrine Prostate Cancer' was performed and relevant articles were reviewed.

EXPERT OPINION

The recent FDA approval and success of 177 PSMA Lutetium in CRPC is promising, as 177 Lutetium could potentially be paired with a NEPC specific biomarker for targeted therapy. Recent laboratory studies pairing DLL3, which is overexpressed in NEPC, with 177 Lutetium and new PET agents have showed good efficacy in identifying and treating NEPC. The success of future development of NEPC therapies may depend on the availability of 177 Lutetium, as current supplies are limited. Further research into additional imaging and treatment options for NEPC is warranted.

Prognostic role of 11C-choline PET/CT scan in patients with metastatic castrate resistant prostate cancer undergoing primary docetaxel chemotherapy

BACKGROUND

We sought to assess the prognostic utility of 11C-choline positron emission tomography/computed tomography (PET/CT) in patients with metastatic castrate resistant prostate cancer (mCRPC) undergoing primary docetaxel chemotherapy.

METHODS

We performed a single institution retrospective analysis of 77 mCRPC patients who were treated with 6 cycles of docetaxel chemotherapy, and who also underwent 11C-choline PET/CT scans at baseline (before chemotherapy), mid-course (after 3 cycles), and posttherapy (after 6 cycles). We evaluated treatment response based on percent change in blood pool-corrected maximum standardized uptake value (SUVmax) of the target lesion on PET/CT, as well as percent change in serum prostate specific antigen (PSA). Logistic regression analysis was used to identify factors associated with complete treatment response. Progression free survival (PFS) analysis was performed using log-rank test and shown on Kaplan-Meier plot.

RESULTS

Percent change in blood pool-corrected SUVmax on mid-course scan was a significant predictor of complete response (odds ratio [OR]: 0.98, 95% confidence interval [CI]: 0.96-0.99, p = .0003), whereas percent change in PSA was not (OR: 0.99, 95% CI: 0.99-1.01, p = .6025). 57 of 77 patients (74%) achieved ≥20% reduction in blood pool-corrected SUVmax on mid-course; these patients were 3.6 times more likely to achieve complete response after full 6 cycles of docetaxel chemotherapy, compared to patients with <20% reduction in blood pool-corrected SUVmax (OR: 3.56, 95% CI: 1.04-16.52, p = .0420). Median PFS in the complete response group was 35.1 months (95% CI: 26.0-52.7 months), compared to 9.4 months (95% CI: 6.9-13.0 months) in the incomplete response group (p = .0005).

CONCLUSIONS

Our study showed that mid-course and posttherapy 11C-choline PET/CT evaluation for mCRPC patients undergoing primary docetaxel chemotherapy can predict full course treatment response and PFS, respectively. 11C-choline PET/CT imaging may provide valuable prognostic information to guide treatment choices for patients with mCRPC.

Phase II Evaluation of Stereotactic Ablative Radiotherapy (SABR) and Immunity in 11C-Choline-PET/CT-Identified Oligometastatic Castration-Resistant Prostate Cancer

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 (T_TR; CD8⁺CD11a^high) predicted superior local, PSA, and distant PFS. Baseline high levels of effector memory T cells (T_EM; CCR7^-CD45RA^-) were associated with improved PSA PFS. An increase in T_TR 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.

Radium-223 in the Third-Line Setting in Metastatic Castration-Resistant Prostate Cancer: Impact of Concomitant Use of Enzalutamide on Overall Survival (OS) and Predictors of Improved OS

INTRODUCTION

Radium-223 (Ra-223) has been recommended for bone-dominant metastatic castration-resistant prostate cancer (mCRPC). Second-generation hormone therapy in combination with Ra-223 in mCRPC has been utilized, yet its benefit has not been well elucidated. We investigated the potential survival benefit of concomitant enzalutamide with Ra-223 in the third-line setting and predictors of improved overall survival (OS).

PATIENTS AND METHODS

We retrospectively identified 51 patients with bone-dominant mCRPC that were treated with Ra-223 in the postchemotherapy and post-hormone therapy setting, either alone (group A; n = 32) or with concomitant enzalutamide (group B; n = 19). The primary endpoint was to study the OS difference between groups A and B. The secondary endpoint was to identify predictors of improved OS with Ra-223 in the third-line setting.

RESULTS

Mean age was 70.9 years, median baseline prostatic-specific antigen (PSA) was 23.1 ng/mL, alkaline phosphatase was 91 IU/L, and hemoglobin was 12.5 g/dL. There was no difference in median OS between groups A and B, at 20.4 versus 17.5 months, respectively (P = .5186). In univariate and multivariate analyses, only pre-Ra-223 PSA < 30 ng/mL and Eastern Cooperative Oncology Group performance status < 2 were associated with improved OS.

CONCLUSION

In our study cohort, concomitant use of enzalutamide with Ra-223 in the mCRPC setting was not associated with improved OS. Only pretreatment PSA < 30 ng/mL and pretreatment Eastern Cooperative Oncology Group performance status < 2 were associated with improved OS. Further prospective studies are warranted.

11C-choline positron emission tomography/computed tomography for detection of disease relapse in patients with history of biochemically recurrent prostate cancer and prostate-specific antigen ≤0.1 ng/ml

Objectives

The objective was to evaluate the diagnostic performance of surveillance¹¹ C-choline positron emission tomography/computed tomography (PET/CT) for the detection of disease relapse in patients with a history of biochemically recurrent (BCR) prostate cancer (PCa) and prostate-specific antigen (PSA) ≤0.1 ng/ml.

Materials and Methods

We included patients who had been treated for BCR PCa and had a surveillance¹¹ C-choline PET/CT at serum PSA ≤0.1 ng/ml. Positive surveillance PET/CT was defined as a study that identified a new tracer-avid lesion or new tracer uptake in a previously treated lesion or both. Findings were confirmed against a composite radiologic-pathologic gold standard. Time to recurrence association analyses were performed for disease relapse risk with the use of Cox proportional hazards regression.

Results

In total, 13 (12.1%) of the 107 patients had positive surveillance PET/CT scans, confirmed on pathologic assessment (n = 5) and subsequent imaging (n = 8). Among these 13 patients, ten had distant metastases, two had local recurrence, and one had both. Nine of the ten patients with metastases had oligometastatic disease defined as the presence of ≤3 metastases. Serum PSA became detectable again in only seven patients with positive surveillance PET/CT, after a mean interval from surveillance PET/CT of 292 days (range: 105-543 days). We identified an association of N stage with increased risk of recurrence (hazard ratio = 3.85; P = 0.036) although this was not significant after accounting for multiple testing.

Conclusions

Surveillance¹¹ C-choline PET/CT can detect early disease relapse at serum PSA ≤0.1 ng/ml in patients with a history of BCR PCa.

Final Analysis of the Ipilimumab Versus Placebo Following Radiotherapy Phase III Trial in Postdocetaxel Metastatic Castration-resistant Prostate Cancer Identifies an Excess of Long-term Survivors

BACKGROUND

The phase 3 trial CA184-043 evaluated radiotherapy to bone metastases followed by Ipilimumab or placebo in men with metastatic castrate-resistant prostate cancer (mCRPC) who had received docetaxel previously. In a prior analysis, the trial's primary endpoint (overall survival [OS]) was not improved significantly.

OBJECTIVE

To report the final analysis of OS.

DESIGN, SETTING, AND PARTICIPANTS

A total of 799 patients were randomized to receive a single dose of radiotherapy to one or more bone metastases followed by either Ipilimumab (n = 399) or placebo (n = 400).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

OS was analyzed in the intention-to-treat population. Prespecified and exploratory subset analyses based on Kaplan-Meier/Cox methodology were performed.

RESULTS AND LIMITATIONS

During an additional follow-up of approximately 2.4 yr since the primary analysis, 721/799 patients have died. Survival analysis showed crossing of the curves at 7-8 mo, followed by persistent separation of the curves beyond that point, favoring the ipilimumab arm. Given the lack of proportional hazards, a piecewise hazard model showed that the hazard ratio (HR) changed over time: the HR was 1.49 (95% confidence interval 1.12, 1.99) for 0-5 mo, 0.66 (0.51, 0.86) for 5-12 mo, and 0.66 (0.52, 0.84) beyond 12 mo. OS rates were higher in the ipilimumab versus placebo arms at 2 yr (25.2% vs 16.6%), 3 yr (15.3% vs 7.9%), 4 yr (10.1% vs 3.3%), and 5 yr (7.9% vs. 2.7%). Disease progression was the most frequent cause of death in both arms. In seven patients (1.8%) in the ipilimumab arm and one (0.3%) in the placebo arm, the primary cause of death was reported as study drug toxicity. No long-term safety signals were identified.

CONCLUSIONS

In this preplanned long-term analysis, OS favored ipilimumab plus radiotherapy versus placebo plus radiotherapy for patients with postdocetaxel mCRPC. OS rates at 3, 4, and 5 yr were approximately two to three times higher in the ipilimumab arm.

PATIENT SUMMARY

After longer follow-up, survival favored the group of men who received ipilimumab, with overall survival rates being two to three times higher at 3 yr and beyond.

A Rare Case of Prostate-Specific Antigen-Producing Metastatic Parotid Adenocarcinoma Developing Androgen Receptor Resistance

A 62-year-old man presented with a rising serum concentration of prostate-specific antigen (PSA) to 53.3 ng/mL (to convert to μg/L, multiply by 1) and a PSA doubling time of 2.6 months. Computed tomography, fluorodeoxyglucose–positron emission tomography, and C-11 choline positron emission tomography demonstrated a parotid mass with innumerable lytic bone lesions and diffuse metastatic disease to the neck and mediastinal lymph nodes. Mediastinal lymph node biopsy revealed salivary ductal adenocarcinoma that produced PSA and demonstrated androgen receptor sensitivity. The patient had a prolonged clinical benefit to first- and second-line hormone therapy, and his PSA levels correlated with treatment response, development of hormone resistance, and progression. In summary, urologists, pathologists, and primary care providers should be aware that a rising PSA level in the setting of a head and neck mass in a patient without a history of prostate cancer does not constitute a diagnosis of metastatic prostate adenocarcinoma and that other primary tumors should be considered and a broader imaging and pathologic evaluation is indicated.

Addition of carboplatin to chemotherapy regimens for metastatic castrate-resistant prostate cancer in post-second generation hormone therapy setting: Does it improve treatment response and survival outcomes?

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Background: The clinical course in metastatic castrate-resistant prostate cancer (mCRPC) can be complicated when patients have disease progression after treatment with 2nd generation hormone therapy (2nd-HT), such as enzalutamide or abiraterone. Currently, limited data exist regarding the optimal choice of chemotherapy for mCRPC after failing 2nd-HT. We sought to evaluate three common chemotherapy regimens in this setting. Methods: We retrospectively identified 150 patients with mCRPC with disease progression on enzalutamide or abiraterone. 92 patients were chemo-naïve, while 58 patients had previously received docetaxel chemotherapy prior to 2nd-HT. After failing 2nd-HT, 90 patients received docetaxel-alone (group A), 33 patients received carboplatin plus docetaxel (group B), while 27 patients received cabazitaxel-alone (Group C). Favorable response was defined by ≥50% reduction in PSA level from baseline after a complete course of chemotherapy. Survival outcome was assessed for 30-month overall survival. Results: Mean (SD) age was 71.2 (8.28), 69.5(8.38) and 67.2 (8.36) for group (A), (B) and (C), respectively. Mean (SD) pre-chemotherapy PSA was 63.8 (138.18), 58.5 (118.15) and 53.7 (88.15) for group (A), (B) and (C), respectively. Mean (SD) Gleason score was 7.9 (1.1), 8.4 (0.88) and 8.1 (1.06) for group (A), (B) and (C), respectively. Patients in group (B) were 2.6 times more likely to have a favorable response compared to group (A) (OR = 2.625, 95%CI: 1.15 - 5.99) and almost 3 times compared to patients in group (C) (OR = 2.975, 95%CI: 1.04 – 8.54) (p-value = 0.0442). We report a Hazard Ratio (HR) of 3.1 (95% CI 1.31-7.35; p = 0.0037) between patients in group (A) versus group (B), and a HR of 4.18 (95% CI 1.58-11.06; p = 0.0037) between patients in group (C) versus group (B). Thirty-month overall survival was 70.7%, 38.9%, and 30.3% for group (B), (A), and (C) respectively (p-value = 0.008). Conclusions: Our data demonstrate improved response and cancer-specific survival in patients with treatment-refractory mCRPC on docetaxel plus carboplatin compared to docetaxel or cabazitaxel alone. Selection bias is inherent in any retrospective study; however, our finding suggests that clinicians may consider docetaxel plus carboplatin in mCRPC patients who fail 2nd-HT. Further prospective studies are warranted.

Radiographic paradoxical response in patients with metastatic castrate-resistant prostate cancer (mCRPC) undergoing treatment with second-generation hormone therapy (second-HT)

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Background: Prostate specific antigen (PSA) has well-recognized limitations as a marker for treatment response and disease progression. A post hoc analysis of the PREVAIL trial reported 24.5% of chemotherapy naïve mCRPC patients on enzalutamide had radiographic progression on conventional imaging with non-rising PSA. In this study, we sought to retrospectively compare PSA levels with C-11 choline positron emission tomography/ computed tomography (PET/CT) images in patients with m-CRPC on 2nd-HT with prior use of chemotherapy. Methods: We identified 123 patients with mCRPC on 2nd-HT following prior use of docetaxel chemotherapy (Abiraterone, n = 106; Enzalutamide, n = 17). Patients underwent serial PSA testing and C-11 choline PET/ CTs every 3–6 months. Disease progression was defined by the increase in blood pool corrected maximum standardized uptake value (SUVmax) of the index lesion on C-11 choline PET/CT scan. Suspicious lesions were confirmed by biopsy and/or conventional imaging. Results: Approximately 43% (n = 53) of patients had radiographic disease progression while on 2nd-HT. At time of radiographic progression, 60.4% of patients showed a parallel rise in PSA (Group-A), while 39.6% showed a paradoxical response; defined as radiographic progression with stable or down-trending PSA (Group-B). Median PSA at time of progression was 3.1 ng/ml for Group-A, and 1.3 ng/ml for Group-B (p-value = 0.0176). Median SUVmax was the same (4.9 Group-A, 4.6 Group-B; p-value = 0.6072). Bone-predominance progression was more significant in Group-B (90%) versus Group-A (65%) (p-value = 0.0309). The median time for radiographic progression was 9.5 months versus 3.9 months for Group-A and Group-B, respectively (Log-Rank = 0.0063). Conclusions: Metabolic imaging is a useful tool that should complement PSA in the evaluation of treatment response and disease progression in mCRPC patients on 2nd-HT, especially considering the paradoxical response observed in our data.

Role of metastases-directed therapy (MDT) in the management of solitary metastatic prostate cancer

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Background: Systemic treatment in the management of metastatic prostate cancer is inevitable. However, there is a growing interest in metastases-directed therapy (MDT). We sought to investigate the efficacy of MDT in treating patients with solitary metastatic prostate cancer and hence, delaying initiation of systemic treatment (i.e., Androgen deprivation therapy or chemotherapy). Methods: We retrospectively identified 61 patients treated with targeted therapy in the form of surgery (n = 30), stereotactic body radiation therapy (SBRT) (n = 25), or cryotherapy (n = 7) for their solitary metastases prostate cancer. Complete response was defined by achieving a PSA value of ≤0.2 ng/ml plus resolution of the solitary metastatic lesion on C-11 choline PET choline scan, while incomplete response was defined by a residual PSA of > 0.2 ng/ml and/or radiographic evidence of disease following metastases-targeted therapy. Results: Mean (±SD) age was 68.4 (±7.8) yrs., median (IQR) primary Gleason Score was 7 (7-9) and median (IQR) pre-MDT PSA was 2 (1.3-3.8) ng/ml. Median (IQR) time from primary treatment of the prostate to MDT was 5.1 (2.7-10.1) years. None of the patients were on hormone therapy at the time of presentation with solitary metastases prostate cancer. 30 patients had bone metastases, 29 patients had lymph node metastases, 1 patient had soft tissue metastasis (pelvic metastatic mass), and another patient had visceral metastasis (to the lung). 42% of the patients (n = 26) achieved complete response to targeted therapy. Median time to initiation of 2nd line systemic treatment following MDT was 17.8 months for the complete responders versus 9.3 months for incomplete responders. 11% of the patients (n = 7) did not require 2nd line therapy after their MDT for a mean (±SD) time of 56.9 (±22.5) months. Conclusions: The use of targeted therapy in the management of patients with solitary metastatic disease or low-volume metastatic disease can provide comparable outcomes to those of systemic treatment. Further studies are warranted.

Non-rising PSA disease progression on C-11 choline PET/CT imaging in patients receiving second generation hormone therapies (2nd-HT)

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Background: Despite having well-recognized limitations, urologists often rely on serial PSA testing as a marker for treatment response or disease progression. To determine if PSA was indeed a reliable marker for treatment response or disease progression, we compared PSA levels against C-11 choline PET/CT in the evaluation of patients with advanced prostate cancer treated with second generation hormonal therapy (2nd-HT). Methods: We retrospectively identified 239 patients who were undergoing treatment with 2nd-HT (enzalutamide or abiraterone) for advanced prostate cancer. While on treatment, patients underwent serial PSA testing and C-11 choline PET/ CTs every 3 – 6 months. Paradoxical response was defined as increasing blood pool-corrected SUVmax of known choline-avid lesions and/or identification of new choline-avid lesions, despite stable or down-trending PSA. Results: Median (IQR) age was 70.4(64.3 – 75.7) years and median (IQR) primary Gleason Score was 8 (7 – 9). In our study, 19% of patients (n = 46/239) who were receiving 2nd-HT exhibited paradoxical response. Median (IQR) PSA and corrected SUVmax at baseline evaluation were 1.3 ng/mL (0.3 – 12.8 ng/mL) and 3.5 (1.8 – 5.8), respectively. Median (IQR) PSA and corrected SUVmax at the time of paradoxical response were 0.4 ng/mL (0.1 – 5.4 ng/mL) and 4.5 (2.8 – 6.8), respectively. The median duration of 2nd-HT treatment prior to detection of paradoxical response was 4.8 months (2.9 – 10.1 months). No significant difference was noted between patients receiving enzalutamide versus abiraterone (p = 0.35). Independent predictors of paradoxical response were prior primary systemic treatment (i.e. hormonal/chemo-hormonal therapy versus local therapy) and patient’s age at time of 2nd-HT initiation on univariate and multivariate analysis. Conclusions: Our retrospective review demonstrated prostate cancer disease progression discordant with PSA down-trending in 19% of patients receiving 2nd-HT. We conclude that in this subset of patients with advanced prostate cancer, PSA may not be a reliable marker of treatment response of disease progression, and routine radiographic evaluation in these patients is warranted.

Concordance of PD-1 and PD-L1 (B7-H1) in paired primary and metastatic clear cell renal cell carcinoma

OBJECTIVES

Previous studies noted discordance of programmed death-1 (PD-1) and one of its ligands (PD-L1) across patient-matched primary and metastatic clear cell renal cell carcinoma (ccRCC). There are inconsistencies if the primary or metastatic tumor has higher expression, and whether metastatic tumor expression is associated with patient outcome. Thus, we examined PD-1 and PD-L1 in patient-matched tumors using a large number of ccRCC patients with long follow-up.

MATERIALS AND METHODS

We analyzed PD-1 and PD-L1 using immunohistochemistry in patient-matched primary and metastatic tumors from 110 ccRCC patients. Concordance was assessed among longitudinal metastatic tumors, as well as across patient-matched primary and metastatic tumors. Cox proportional hazards regression was used to evaluate the associations of metastatic tumor expression with cancer-specific survival.

RESULTS

We observed inter-metastatic tumor heterogeneity of PD-1 in 25 (69%) of the 36 patients and of PD-L1 in seven (19%) patients. Concordance between patient-matched primary and metastatic tumors was 73% (Kappa = 0.16, 95% CI: -0.003-0.32). Similarly, concordance of PD-L1 between metastatic and patient-matched primary tumors was 78% (Kappa = 0.27, 95% CI: 0.09-0.46). Both markers demonstrated higher expression in primary vs metastatic tumors. Metastatic tumor expression of PD-1 was significantly associated with metastatic location (P < .0001) and ccRCC-specific survival (HR = 2.15, 95% CI: 1.06-4.36, P = .035).

CONCLUSIONS

The expression of PD-1 and PD-L1 is discordant across patient-matched ccRCC tumors, with higher expression in primary tumors. Higher PD-1 expression was associated with metastatic location and lower cancer-specific survival. If validated, these results highlight the importance of evaluating these biomarkers in metastatic tissue specifically.

11C-Choline PET Guided Salvage Radiation Therapy for Isolated Pelvic and Paraortic Nodal Recurrence of Prostate Cancer After Radical Prostatectomy: Rationale and Early Genitourinary or Gastrointestinal Toxicities

Purpose

To assess gastrointestinal (GI) and genitourinary (GU) adverse events (AEs) of ¹¹C-choline-positron emission tomography (CholPET) guided lymph node (LN) radiation therapy (RT) in patients who experience biochemical failure after radical prostatectomy.

Methods and Materials

From 2013 to 2016, 107 patients experienced biochemical failure of prostate cancer, had CholPET-detected pelvic and/or paraortic LN recurrence, and were referred for RT. Patients received androgen suppression and CholPET guided LN RT (median dose, 45 Gy) with a simultaneous integrated boost to CholPET-avid sites (median dose, 56.25 Gy), all in 25 fractions. RT-naïve patients had the prostatic fossa included in the initial treatment volumes followed by a sequential boost (median dose, 68 Gy). GI and GU AEs were reported per Common Terminology Criteria for Adverse Events (version 4.0) with data gathered retrospectively. Differences in maximum GI and GU AEs at baseline, immediately post-RT, and at early (median, 4 months) and late (median, 14 months) follow-up were assessed.

Results

Median follow-up was 16 months (interquartile range [IQR], 11-25). Median prostate-specific antigen at time of positive CholPET was 2.3 ng/mL (IQR, 1.3-4.8), with a median of 2 (IQR, 1-4) choline-avid LNs per patient. Most recurrences were within the pelvis (53%) or pelvis + paraortic (40%). Baseline rates of grade 1 to 2 GI AEs were 8.4% compared with 51.9% (4.7% grade 2) of patients post-RT (P < .01). These differences resolved by 4-month (12.2%, P = .65) and 14-month AE assessments (9.1%, P = .87). There was no significant change in grade 1 to 2 GU AEs post-RT (64.1%) relative to baseline (56.0%, P = .21), although differences did arise at 4-month (72.2%, P = .01) and 14-month (74.3%, P = .01) AE assessments.

Conclusions

Salvage CholPET guided nodal RT has acceptably low rates of acute GI and GU AEs and no significant detriment in 14-month GI AEs. These data are of value in counseling patients and designing prospective trials evaluating the oncologic efficacy of this treatment strategy.

Corrigendum to "Targeting B7-H1 (PD-L1) sensitizes cancer cells to chemotherapy" [Heliyon 4 (12) (December 2018) e01039]

[This corrects the article DOI: 10.1016/j.heliyon.2018.e01039.].

Percutaneous Image-Guided Nodal Biopsy After 11C-Choline PET/CT for Biochemically Recurrent Prostate Cancer: Imaging Predictors of Disease and Clinical Implications

Purpose

Management of recurrent prostate cancer necessitates timely diagnosis and accurate localization of the sites of recurrent disease. The purpose of this study was to assess predictors of histologic outcomes after 11C-choline positron emission tomography/computed tomography (CholPET) to increase the positive predictive value and specificity of CholPET in identifying imaging predictors of malignant and benign nodal disease to better inform clinical decision making regarding local therapy planning.

Materials and Methods

Retrospective review of patients undergoing CholPET followed by percutaneous core needle biopsy between January 1, 2010 and January 1, 2016. A total of 153 patients were identified who underwent 166 biopsy procedures. Patient, CholPET, procedural, and pathologic characteristics were recorded.

Results

A total of 157 biopsies were technically successful, and 110 (70.1%; 95% confidence interval, 62.2-77.1) yielded histologic results abnormal for metastatic prostate cancer. Lesion location, lesion maximum standardized uptake value (SUVmax), SUV ratio (calculated as the ratio of SUVmax to SUV mean in the right atrium), prostate-specific antigen, lesion short axis length, total Gleason score, and castration resistance were all associated with abnormal biopsy results (P values <.001, <.001, <.001, .02, .02, .02, and .015, respectively). External iliac, common iliac, and inguinal sites were associated with much lower rates of histologic positivity (mean [95% confidence interval], 51.2% [35.1-67.1], 46.2% [19.2-74.9], and 33.3% [7.5-70.1]), respectively.

Conclusions

In a cohort of patients in whom core needle biopsy was performed after CholPET, characteristics of choline localization including node location, SUVmax, lesion–to–blood pool SUV ratio, prostate-specific antigen, total Gleason score, and castration resistance were significantly associated with abnormal biopsy results for metastatic disease on CholPET. Relatively high false positive rates were found in common iliac, external iliac, and inguinal lymph node locations. Histologic confirmation of these sites should be strongly considered in the appropriate clinical scenario before designing additional local therapy plans.

Targeting B7-H1 (PD-L1) sensitizes cancer cells to chemotherapy

Development of resistance to chemotherapy is a major obstacle in extending the survival of patients with cancer. Although originally defined as an immune checkpoint molecule, B7-H1 (also named as PD-L1 or CD274) was found to play a role in cancer chemoresistance; however, the underlying mechanism of action of B7-H1 in regulation of chemotherapy sensitivity remains unclear in cancer cells. Here we show that development of chemoresistance depends on an increased activation of ERK in cancer cells overexpressing B7-H1. Conversely, B7-H1 knockout (KO) by CRISPR/Cas9 renders human cancer cells susceptible to chemotherapy in a cell-context dependent manner through a reduced activation of p38 MAPK. B7-H1 was found to associate with the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) and this association promoted or maintained the activation of ERK or p38 MAPK in cancer cells. Importantly, we found that targeting B7-H1 by anti-B7-H1 monoclonal antibody (H1A) increased the sensitivity of human triple negative breast cancer cells to cisplatin therapy in vivo. Our results suggest that targeting B7-H1 by an antibody capable of disrupting B7-H1 signals may be a new approach to sensitize cancer cells to chemotherapy.

Prospective Immunophenotyping of CD8+ T Cells and Associated Clinical Outcomes of Patients With Oligometastatic Prostate Cancer Treated With Metastasis-Directed SBRT

PURPOSE

This study examined the effects of metastasis-directed stereotactic body radiation therapy (mdSBRT) on CD8⁺ T-cell subpopulations and correlated post-mdSBRT immunophenotypic responses with clinical outcomes in patients with oligometastatic prostate cancer (OPCa).

METHODS AND MATERIALS

Peripheral blood mononuclear cells were prospectively isolated from 37 patients with OPCa (≤3 metastases) who were treated with mdSBRT. Immunophenotyping identified circulating CD8⁺ T-cell subpopulations, including tumor-reactive (T_TR), effector memory, central memory (T_CM), effector, and naïve T cells from samples collected before and after mdSBRT. Univariate Cox proportional hazards regression was used to assess whether changes in these T-cell subpopulations were potential risk factors for death and/or progression. The Kaplan-Meier method was used for survival. Cumulative incidence for progression and new distant metastasis weas estimated, considering death as a competing risk.

RESULTS

Median follow-up was 39 months (interquartile range, 34-43). Overall survival at 3 years was 78.2%. Cumulative incidence for local progression and new distant metastasis at 3 years was 16.5% and 67.6%, respectively. Between baseline and day 14 after mdSBRT, an increase in the T_CM cell subpopulation was associated with the risk of death (hazard ratio, 1.22 [95% confidence interval, 1.02-1.47]; P = .033), and an increase in the T_TR cell subpopulation was protective against the risk of local progression (hazard ratio, 0.80 [95% confidence interval, 0.65-0.98]; P = .032).

CONCLUSIONS

An increase in the T_TR cell subpopulation was protective against the risk of disease progression, and an increase in the T_CM cell subpopulation was associated with the risk of death in patients with OPCa treated with mdSBRT. Disease control may be further improved by better understanding the CD8⁺ T-cell subpopulations and by enhancing their antitumor effect.

Identification of Recurrence Sites Following Post-Prostatectomy Treatment for Prostate Cancer Using 11C-Choline Positron Emission Tomography and Multiparametric Pelvic Magnetic Resonance Imaging

PURPOSE

We describe anatomical sites of recurrence in patients with prostate cancer who had biochemical recurrence following radical prostatectomy and who received radiotherapy and/or androgen deprivation therapy postoperatively. We performed ¹¹C-choline positron emission tomography/computerized tomography and multiparametric magnetic resonance imaging.

MATERIALS AND METHODS

After radiotherapy and/or androgen deprivation therapy patients who underwent radical prostatectomy were evaluated by ¹¹C-choline positron emission tomography/computerized tomography and multiparametric magnetic resonance imaging to determine recurrence patterns and clinicopathological features. Recurrent sites were described as local only (seminal vesicle bed/prostate fossa, vesicourethral anastomosis and bladder neck) or distant metastatic disease. Features associated with the identification of any distant metastatic disease were evaluated by multivariable logistic regression.

RESULTS

A total of 550 patients were identified. Treatment included androgen deprivation therapy in 108, radiotherapy in 201, and androgen deprivation therapy and radiotherapy in 241. Median prostate specific antigen at evaluation was 3.9, 3.6 and 2.8 ng/ml in patients treated with androgen deprivation therapy, radiotherapy and a combination, respectively. Recurrence developed locally in 77 patients (14%), as distant metastasis only in 411 (75%), and as local and distant metastatic disease in 62 (11%). On multivariable analysis treatment with radiotherapy (OR 7.18, 95% CI 2.92-17.65), and radiotherapy and hormonal therapy (OR 9.23, 95% CI 3.90-21.87, all p <0.01) was associated with increased odds of distant failure at evaluation.

CONCLUSIONS

The combination of ¹¹C-choline positron emission tomography/computerized tomography and multiparametric magnetic resonance imaging successfully identified patterns of recurrence after postoperative radiotherapy and/or androgen deprivation therapy at a median prostate specific antigen of less than 4 ng/ml. Half of this cohort had local only recurrence and/or a low disease burden limited to pelvic lymph nodes. These patients may benefit from additional local therapy. These data and this analysis may facilitate the evaluation of such patients with biochemically recurrent prostate cancer.

Retrospective Review of Percutaneous Image-Guided Ablation of Oligometastatic Prostate Cancer: A Single-Institution Experience

PURPOSE

To retrospectively review and report the efficacy and safety of percutaneous image-guided ablation (cryoablation or radiofrequency ablation) in the treatment of oligometastatic prostate cancer.

MATERIALS AND METHODS

An institutional registry was retrospectively reviewed and revealed 16 patients with oligometastatic prostate cancer (median age, 67 y; range, 50-86 y) who underwent percutaneous image-guided ablation to treat 18 metastatic sites. A subgroup of 7 patients with 8 metastases were androgen-deprivation therapy (ADT)-naïve and underwent ablation to delay initiation of ADT. Local tumor control, progression-free survival (PFS), ADT-free survival, and procedural complications were analyzed.

RESULTS

Local tumor control was achieved in 15 of 18 metastases (83%) at a median follow-up of 27 months (range, 5-56 mo). Local tumor recurrence was found in 3 of 18 metastases (17%), with a median time to local recurrence of 3.5 months (range, 3-38 mo). Estimated PFS rates at 12 and 24 months were 56% (95% confidence interval [CI], 30%-76%) and 43% (95% CI, 19%-65%), respectively. In the 7 ADT-naïve patients, local tumor control was achieved in all metastases, and the median ADT-free survival period was 29 months. There were no major procedural complications.

CONCLUSIONS

In this cohort of patients with oligometastatic prostate cancer, percutaneous image-guided ablation was feasible and well tolerated and achieved acceptable local tumor control rates. Percutaneous ablation may be of particular utility in patients who wish to delay initiation of ADT.

Patterns of Recurrence After Postprostatectomy Fossa Radiation Therapy Identified by C-11 Choline Positron Emission Tomography/Computed Tomography

PURPOSE

To evaluate C-11 choline positron emission tomography/computed tomography (CholPET) in staging and determining patterns of recurrence in prostate cancer patients with rising prostate-specific antigen levels after prostatectomy radiation therapy (RT).

METHODS AND MATERIALS

The study includes patients with biochemical failure after postprostatectomy RT who underwent CholPET between 2008 and 2015. Patient and disease characteristics were examined in relation to sites of recurrence. All RT dosimetry records were reviewed, and recurrences were mapped on a representative computed tomography dataset with their relationship relative to the irradiated fossa field as out of field (OOF), edge of field (EOF; recurrence within <45-Gy isodose lines), or in field (IF; recurrence within ≥45-Gy isodose lines).

RESULTS

Forty-one patients were identified with 121 sites of recurrence (median 2 sites; interquartile range [IQR], 1-4). The median prostate-specific antigen level at CholPET was 3.1 (IQR, 1.9-5.6) ng/mL. Median interval from RT to biochemical failure was 24 (IQR, 10-46) months, with recurrence identified on CholPET at a median of 15 (IQR, 7-28) months from biochemical failure. Histologic confirmation of recurrence was obtained in 20 patients (49%), with the remainder confirmed by treatment response. Five patients (12%) had IF recurrences, 10 patients (24%) had EOF recurrences (median dose 10 Gy; IQR, 5-30 Gy), and 36 patients (88%) had OOF recurrences. Ten patients had combination failures: 6 (15%) EOF/OOF and 4 (10%) IF/OOF. Fifty-seven recurrences (47%) were pelvic nodal sites inferior to the L5-S1 interspace, of which 52 (43%) were within a pelvic RT field. Eighty-one recurrences (67%) were nodal and inferior to the aortic bifurcation.

CONCLUSIONS

Using CholPET, we found that the majority of patients evaluated for biochemical failure recurred outside of the postprostatectomy RT field. Furthermore, most recurrence sites were nodal and inferior to the aortic bifurcation. These results provide data that may be useful for examining strategies that include elective lymph node irradiation in postprostatectomy patients.

Randomized, Double-Blind, Phase III Trial of Ipilimumab Versus Placebo in Asymptomatic or Minimally Symptomatic Patients With Metastatic Chemotherapy-Naive Castration-Resistant Prostate Cancer

Purpose Ipilimumab increases antitumor T-cell responses by binding to cytotoxic T-lymphocyte antigen 4. We evaluated treatment with ipilimumab in asymptomatic or minimally symptomatic patients with chemotherapy-naive metastatic castration-resistant prostate cancer without visceral metastases. Patients and Methods In this multicenter, double-blind, phase III trial, patients were randomly assigned (2:1) to ipilimumab 10 mg/kg or placebo every 3 weeks for up to four doses. Ipilimumab 10 mg/kg or placebo maintenance therapy was administered to nonprogressing patients every 3 months. The primary end point was overall survival (OS). Results Four hundred patients were randomly assigned to ipilimumab and 202 to placebo; 399 were treated with ipilimumab and 199 with placebo. Median OS was 28.7 months (95% CI, 24.5 to 32.5 months) in the ipilimumab arm versus 29.7 months (95% CI, 26.1 to 34.2 months) in the placebo arm (hazard ratio, 1.11; 95.87% CI, 0.88 to 1.39; P = .3667). Median progression-free survival was 5.6 months in the ipilimumab arm versus 3.8 with placebo arm (hazard ratio, 0.67; 95.87% CI, 0.55 to 0.81). Exploratory analyses showed a higher prostate-specific antigen response rate with ipilimumab (23%) than with placebo (8%). Diarrhea (15%) was the only grade 3 to 4 treatment-related adverse event (AE) reported in ≥ 10% of ipilimumab-treated patients. Nine (2%) deaths occurred in the ipilimumab arm due to treatment-related AEs; no deaths occurred in the placebo arm. Immune-related grade 3 to 4 AEs occurred in 31% and 2% of patients, respectively. Conclusion Ipilimumab did not improve OS in patients with metastatic castration-resistant prostate cancer. The observed increases in progression-free survival and prostate-specific antigen response rates suggest antitumor activity in a patient subset.

Contemporary Mapping of Post-Prostatectomy Prostate Cancer Relapse with 11C-Choline Positron Emission Tomography and Multiparametric Magnetic Resonance Imaging

PURPOSE

We identify sites and patterns of cancer recurrence in patients with post-prostatectomy biochemical relapse using ¹¹C-choline positron emission tomography/computerized tomography and endorectal coil multiparametric magnetic resonance imaging.

MATERIALS AND METHODS

Between January 2008 and June 2015, 2,466 men underwent choline positron emission tomography for suspected prostate cancer relapse at our institution. Of these men 202 did not receive hormone or radiation therapy, underwent imaging with choline positron emission tomography and multiparametric magnetic resonance imaging, and were found to have disease recurrence. Overall patterns of recurrence were described, and factors associated with local only recurrence were evaluated using univariable and multivariable logistic regression.

RESULTS

Median prostate specific antigen at positive scan was 2.3 ng/ml (IQR 1.4-5.5) with a median time from prostate specific antigen relapse to lesion visualization of 15 months (IQR 4.8-34.2). Of these 202 men 68 (33%) exhibited local only, 45 (22%) local plus metastatic and 89 (45%) metastatic only relapse. Pelvic node only relapse was observed in 39 (19%) men. Median prostate specific antigen at positive imaging for patients with local only, metastatic only and local plus metastatic relapse was 2.3, 2.7 and 2.2 ng/ml (p=0.46), with a median interval from biochemical recurrence to positive scan of 33.5, 7.0 and 15.0 months, respectively (p <0.001). On multivariable analysis time from biochemical recurrence to positive imaging was independently associated with local only recurrence (OR 1.10 for every 6-month increase, p=0.012).

CONCLUSIONS

Combined choline positron emission tomography and multiparametric magnetic resonance imaging evaluation of biochemical recurrence after prostatectomy reveals an anatomically diverse pattern of recurrence. These findings have implications for optimizing the salvage treatment of patients with prostate cancer with relapse following surgery.

Stereotactic Body Radiation Therapy for Oligometastatic Prostate Cancer

PURPOSE

To review outcomes of patients with oligometastatic prostate cancer (PCa) treated with stereotactic body radiation therapy (SBRT) and to identify variables associated with local failure.

METHODS AND MATERIALS

We retrospectively reviewed records of patients treated with SBRT for oligometastatic PCa. Metastasis control (ie, control of the treated lesion, MC), biochemical progression-free survival, distant progression-free survival, and overall survival were estimated with the Kaplan-Meier method.

RESULTS

Sixty-six men with 81 metastatic PCa lesions, 50 of which were castrate-resistant, were included in the analysis. Lesions were in bone (n=74), lymph nodes (n=6), or liver (n=1). Stereotactic body radiation therapy was delivered in 1 fraction to 71 lesions (88%), at a median dose of 16 Gy (range, 16-24 Gy). The remaining lesions received 30 Gy in 3 fractions (n=6) or 50 Gy in 5 fractions (n=4). Median follow-up was 16 months (range, 3-49 months). Estimated MC at 2 years was 82%. Biochemical progression-free survival, distant progression-free survival, and overall survival were 54%, 45%, and 83%, respectively. On multivariate analysis, only the dose of SBRT was significantly associated with MC; lesions treated with 16 Gy had 58% MC, and those treated with ≥18 Gy had 95% MC at 2 years (P≤.001). At 2 years, MC for lesions treated with 18 Gy (n=21) was 88%. No patient treated with ≥18 Gy in a single fraction or with any multifraction regimen had local failure. Six patients (9%) had grade 1 pain flare, and 2 (3%) had grade 2 pain flare. No grade 2 or greater late toxicities were reported.

CONCLUSIONS

Stereotactic body radiation therapy for patients with oligometastatic prostate cancer provided optimal metastasis control and acceptable toxicity with doses ≥18 Gy. Biochemical progression-free survival was 54% at 16 months with the inclusion of SBRT in the treatment regimen. Stereotactic body radiation therapy should be considered in patients with castration-refractory, oligometastatic prostate cancer who have limited options for systemic therapy.

Immunotherapy in prostate cancer

Immunotherapy for the treatment of malignant neoplasms has made significant progress over the last 20 years. Multiple molecular targets and clinical agents have been developed recently, particularly in the field of metastatic adenocarcinoma of the prostate. Sipuleucel-T is currently the only FDA approved immunotherapy for prostate cancer. PSA-TRICOM (Prostvac) currently has a phase III randomized trial underway after a phase II trial showed an improvement in overall survival. Interestingly, both these agents showed improvement in overall survival with no measurable change in disease state, leading to significant controversy as the utility of these agents in prostate cancer. Ipilimumab revealed a benefit for a sub-cohort of men in a post-docetaxel group and is currently undergoing investigation in a pre-docetaxel group. There are a number of other targets such as PD-1 which have shown effectiveness in other neoplasms that will likely be investigated in the future for use in prostate cancer.

Impact of single agent daily prednisone on survival and toxicities in post-docetaxel men with metastatic castration-resistant prostate cancer (mCRPC): An analysis of 2 phase III trials

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Background: Daily oral prednisone (P) has been employed for the therapy of mCRPC, alone or in combination regimens. Despite palliative benefits and PSA responses, the overall clinical impact of P is unknown and it may foster resistance mechanisms. We performed a pooled analysis of control arms of randomized trials which either did or did not administer single agent P to evaluate its impact on overall survival (OS) and toxicities. Methods: Individual patient data from control arms ofrandomized trials of post-docetaxel men receiving placebo or P + placebo were eligible for analysis. Patient demographics, survival, and toxicity data were collected. The impact of P on OS and toxicities was investigated in Cox regression models adjusted for known clinical and laboratory prognostic factors. Statistical significance was defined as a p-value < 0.05 and all tests were two-sided. Results: The control arms of 2 randomized phase III trials were available totaling 794 men: the COU-AA-301 trial (n = 394) administered P plus placebo and the CA184-043 trial (n = 400) administered placebo alone. P plus placebo was not significantly associated with OS compared to placebo alone in a multivariable analysis (HR = 0.89 [95% CI 0.72-1.10], p = 0.27). Other factors associated with poor OS were Eastern Cooperative Oncology group (ECOG)-performance status (PS) ≥ 1, Gleason Score ≥ 8, liver metastasis, high PSA, hypoalbuminemia, and elevated LDH.In contrast, CTCAE grade ≥ 3 therapy-related toxicities were significantly increased with P plus placebo compared to placebo alone (HR = 1.48 (1.03-2.13), p = 0.034) in a multivariable analysis. Other baseline factors significantly associated with a higher risk of grade ≥ 3 toxicities were ECOG-PS ≥ 1, hypoalbuminemia and elevated LDH. Conclusions: P plus placebo compared with placebo alone for post-docetaxel men with mCRPC was not associated with extension of OS, but was associated with higher grade ≥ 3 toxicities. With the exception of the use of P in combination with abiraterone, P alone or in combination regimens should be questioned given its unclear palliative benefits and association with increased toxicities.

Mapping prostate cancer (CaP) recurrence after prostatectomy with c-11 choline PET/CT and 3T pelvic MRI in the contemporary era

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Background: The purpose of this study was to identify site-specific recurrence patterns for patients (pts) with biochemical recurrence (BCR) after prostatectomy (RP) using C-11 Choline PET/CT (C11Ch) and 3T pelvic MRI with endorectal coil (pMRI). Methods: Between 2008 and 2006, 2,466 men underwent C11Ch and pMRI for BCR after RP. From this cohort, we identified 261 pts who received no adjuvant or salvage therapy (androgen deprivation or radiation). Suspected radiographic relapse was confirmed by biopsy (46%) or progression/response to treatment in concordance with subsequent rise/decline in PSA (54%). Results: Of the 261 men evaluated, 202 (75%) had positive pMRI, C11Ch or both. Seventy nine (39%), 105 (52%) and 18 (9%) pts had high, intermediate, and low risk CaP, respectively at RP. Median PSA at the time of positive scan was 2.3 ng/mL, with a median time from BCR to radiographic disease identification of 15 months. Of these 202 men, 67 (33%) harbored prostate fossa recurrence only, 44 (22%) had a combination of local and metastatic disease and 91 (45%) had metastatic disease without local recurrence. Forty (20%) pts had pelvic nodal recurrence only and 18 (9%) had perirectal nodal involvement. Median PSA for pts with local only recurrence, distant metastases only, and local + distant disease was 2.3, 2.7 and 2.2 ng/mL, respectively, with a median interval from BCR to positive scan of 16.7, 7.9 and 11 months. Imaging revealed that 33% to 66% of our cohort would have all sites of disease treated by salvage RT depending on the extent of the treatment field Conclusions: C11Ch and pMRI were used to identify recurrence patterns in pts with BCR after RP only. At median PSA of 2.3 ng/ml, our study demonstrates a low rate of local-only recurrence, higher than anticipated frequency of metastatic recurrence with peak frequency within the pelvic lymph nodes, and substantial perirectal recurrences. Despite the high rates of distant recurrences, 2/3 of our cohort had their disease limited to the pelvis and could be potential candidates for local therapies, including salvage radiation.

Abstract 10: Concordance of BAP1, PBRM1, Ki-67, and TOPOIIa protein expression in primary clear cell renal cell carcinoma tumors and patient-matched metastatic tumors

Introduction: Efforts to improve clear cell renal cell carcinoma (ccRCC) mortality have focused primarily on evaluating prognostic biomarkers in primary tumors in order to identify indicators of response to treatment and targets for novel therapies. To date little attention has been paid to the status of these biomarkers in the more therapeutically-relevant metastatic tumor. Thus, we evaluated concordance of expression of four key prognostic ccRCC biomarkers (BAP1, PBRM1, Ki-67 and TOPOIIa) in a large cohort of patient-matched primary ccRCC and metastatic tumors.

Methods: We identified 114 patients treated surgically for ccRCC between 1990 and 2005 who had synchronous (M1) or metachronous (M0) metastases, underwent metastasectomy for at least one metastatic lesion and had archived tissue available from the primary and at least one metastatic tumor. We performed IHC on all primary and metastatic tumors for BAP1, PBRM1, Ki-67, and TOPOIIa using previously-published protocols. BAP1 and PBRM1 expression was categorized as positive or negative and Ki-67 and TOPOIIa was quantified as the number of positive cells per mm2. For BAP1 and PBRM1, we calculated the concordance between patient-matched primary and metastatic tumors as the percentage of pairs where the primary and metastatic tumor had the same designation (i.e., positive or negative). For TOPOIIa and Ki-67, we assessed concordance using Spearman correlation coefficient. Analysis of variance was used to evaluate if concordance between primary-metastatic tumor pairs for TOPOIIa and Ki-67 was associated with metastatic site, metastatic timing (M0/M1), metastatic tumor grade, metastatic tumor necrosis, and metastatic tumor sarcomatoid differentiation.

Results: There were a total of 161 patient-matched metastatic tumors available for the 114 patients: 78 patients had only a single metastasis while 36 patients had two or more metastases. While sites of metastases varied, pulmonary metastases were the most common (44% of all metastases). Loss of BAP1 expression was observed in19% of the primary ccRCC and 98.6% of the tumor pairs had concordant BAP1 status between the paired primary and metastatic tumors. Loss of PBRM1 was observed in 56% of the primary ccRCC tumors and 89.3% of tumor pairs showed concordant PBRM1 status. By comparison, median expression of Ki-67 was 65.0mm2 in the primary ccRCC tumors and the Pearson correlation with the patient-matched metastatic tumors was 0.43. The difference in Ki-67 expression between primary-metastatic tumor pairs was associated with necrosis in the metastatic tumor (p=0.014). Median expression of TOPOIIa was 2.6mm2 in the primary ccRCC tumors and the Pearson correlation with the patient-matched metastatic tumors was 0.25. The difference in TOPOIIa expression between primary-metastatic tumor pairs was associated with metastatic site (p=0.0006) and metastases to the heart were significantly different than pulmonary metastases (p&lt;0.0001). Additionally, synchronous metastases had larger differences from their patient-matched primary tumors in comparison to metachronous metastases (p=0.012), as did necrotic metastases (p=0.028).

Conclusion: We observed high concordance for loss of BAP1 and PBRM1 expression between primary ccRCC and metastatic tumors in the same patient. Conversely, we noted high discordance in protein expression of Ki-67 and TOPOIIa between patient-matched primary-metastatic tumor pairs. Moreover, this discordance varied by key pathological features. Our results suggest that using the status of a biomarker in primary ccRCC as a guide for the status in metastatic tumors is not always appropriate and needs to be evaluated on a marker-by-marker basis.

Citation Format: Jeanette E. Eckel-Passow, Daniel J. Serie, John C. Cheville, Thai H. Ho, Sue M. Harrington, Tracy Hilton, Christine Lohse, Amanda Shreders, Payal Kapur, James Brugarolas, R Houston Thompson, Bradley C. Leibovich, Eugene D. Kwon, Richard W. Joseph, Alexander S. Parker. Concordance of BAP1, PBRM1, Ki-67, and TOPOIIa protein expression in primary clear cell renal cell carcinoma tumors and patient-matched metastatic tumors. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Integrating Clinical Genomics and Cancer Therapy; Jun 13-16, 2015; Salt Lake City, UT. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(1_Suppl):Abstract nr 10.