Citations

e14576 Background: Immune checkpoint inhibitors (ICI) have revolutionized the treatment of many solid malignancies. ICI appears particularly effective when tumors exhibit high microsatellite instability (MSI-H) and/or mismatch repair deficient (dMMR) status. Although the response is typically quite good in this setting, there are scenarios where benefit is less than anticipated. In this study, we aimed to explore the efficacy of ICIs in patients with MSI-H/dMMR cancers with peritoneal metastasis (PM). Methods: We conducted a retrospective chart review to identify patients (pts) with PM from primary MSI-H/dMMR cancers treated with immunotherapy between 2010 and 2022 at Mayo Clinic. Data was collected to include pt demographics, tumor characteristics, pathology, tumor markers, imaging, mutational profile, and previous and subsequent treatments. The primary endpoint was disease control rate (DCR), defined as objective response rate (RECIST v1.1 criteria) or stable disease. Results: Forty-six pts with MSI-H/dMMR and PM treated with ICIs. Most of our cohort were female (61%) with a median age at diagnosis of 61 years. Colorectal cancer was the most common primary site (69.6%), followed by endometrial (6.5%). Most pts received treatment with PD-1 antibodies as second-line therapy following systemic chemotherapy. DCR of the PM was 71.6 % (n= 13 PR, 9 CR, and 9 SD), with a median duration of response of 12.6 months. Thirteen pts (28.4%) had progressive peritoneal disease on ICI with a median PFS of 2.2 months. Ascites was a poor prognosticator and predicted a lack of benefit from ICI (HR 6.6, 95% CI=2.24-19.9, p= 0.006). Mucinous and signet ring histology were common in pts with peritoneal progression (61.5%); however, this was not statistically significant (HR=1.6; 95%CI= 0.4383 to 3.899, p 0.5). Multivariate analysis for the presence or absence of BRAF and/or RAS mutations was not statistically significant in predicting response. Neither was the specific MMR gene mutation(i.e., MLH1 or PMS2). Interestingly, discordant responses between the peritoneum and other sites of metastasis to immunotherapy were seen in 13 pts (28.4%), primarily as primary peritoneal progression compared to other tumor sites. Conclusions: In our cohort, the DCR of metastatic peritoneal disease in MSI-H/dMMR tumors was approximately 71%. The presence of ascites was identified as a poor prognosticator in this setting and was associated with a lack of response/benefit from ICIs. Histologic subtype (i.e., mucinous/signet ring) did not show statistical significance in predicting ICI response. The subpopulation with discordant response to ICI suggests that peritoneal immunobiology may differ from other sites. Further research on immunotherapy response in the peritoneum is needed for this special subset of pts.

Objectives Somatostatin receptor (SSTR) PET imaging is utilized with increasing frequency in the clinical management of neuroendocrine tumors. Incidental PET-avid CNS lesions are commonly noted and presumed to be meningiomas. However, SSTR PET lacks specificity for meningioma identification. This study aimed to clarify the role of SSTR-based imaging in the classification of incidental CNS lesions based on current clinical practice. Methods Patients who underwent both Ga-68-DOTATATE PET and brain MRI and had an incidental CNS lesion identified with a radiographic prediction of meningioma via one (discordant prediction) or both (concordant prediction) imaging modalities were retrospectively analyzed. Imaging indication, semiquantitative measures, and clinical history were recorded. Results Among 48 patients with a CNS lesion identified on both imaging modalities, most scans were performed for a history of neuroendocrine tumor (64.6%). Cases with concordant lesion-type prediction of meningioma between imaging modalities (N = 24) displayed a significantly higher SUV max (median 7.9 vs. 4.0; P = 0.008) and Krenning score (median 3.0 vs. 2.0; P = 0.005) on Ga-68-DOTATATE PET compared with cases with a discordant prediction of meningioma (N = 24). In cases with lower SUV max values, Ga-68-DOTATATE was more likely to discordantly predict meningioma without agreement by the corresponding MRI. Prior cranial radiation or use of somatostatin mimetics did not affect quantitative radiographic measures, and MRI-based tumor size was similar across groups. Conclusion Lesions with increased avidity may be more confidently predicted as meningioma in Ga-68-DOTATATE PET scans, whereas there is more discrepancy in prediction among low SUV cases.

Abstract Poorly differentiated extrapulmonary neuroendocrine carcinomas (EP NECs) are aggressive cancers characterized by a high Ki‐67 index, rapid tumor growth and poor survival, and are subdivided into small and large cell carcinoma. For small cell carcinoma of the lung, a pulmonary NEC, the combination of cytotoxic chemotherapy (CTX) and a checkpoint inhibitor (CPI) is considered standard therapy and superior to CTX alone. EP NECs are typically treated with platinum‐based regimens, some clinicians have adopted the addition of a CPI to CTX based on data from trials in patients with small cell carcinoma of the lung. In this retrospective study of EP NECs, we report 38 patients treated with standard first‐line CTX and 19 patients treated with CTX plus CPI. We did not observe any additional benefit of adding CPI to CTX in this cohort.

Abstract Introduction: Clonal hematopoiesis (CH) is defined by acquisition of somatic mutations in hematopoietic stem cells with potential for expansion over time. CH is influenced by exposures to chemotherapy/radiation & has been associated with therapy related myeloid neoplasms (tMN). Peptide receptor radionuclide therapy (PRRT) is a radionuclide therapy and is FDA approved for neuroendocrine tumors (NET). PRRT has been associated with a 2-10% risk of tMN, especially with prior exposure to alkylating agents. A prior study of 13 NET patients found CH prevalence of 64%. We carried out a prospective assessment of CH in NET patients prior to PRRT. Methods: We evaluated pre-PRRT blood samples in 37 NET patients. Genomic DNA from mononuclear cells was analyzed for CH using a custom panel targeting 229 genes to a targeted depth of >1000X. Results: After approval by Mayo Clinic IRB, 45 patients with Stage IV NET were enrolled & CH data was available for 37. Fifty-one percent of patients were female, with a median age of 68yrs (range, 34-84yrs). Types of NET included small bowel (51%), pancreatic (29%), carcinoid (8%), paraganglioma (5%), & other (5%). The median number of therapies prior to PRRT was 1 (range, 0-4) & included somatostatin analogues (SSA)-81%, alkylating agents-30%, & prior radiation-13%. Thirty-six of 37 patients had variants identified, 5 of which were presumed germline (DDX41, CDKN2B, CHEK2, POT1, ERBB2), & 17 (45.9%) had pathogenic variants meeting the operational definition of CH (DNMT3A, TET2, PPM1D, TP53, SF3B1, ASXL1). The median number of pathogenic variants per patient was 1 (range, 0-2), & 6 patients had >1. In patients >60yrs old, 46% had pathogenic variants & 3 patients with pathogenic variants (TET2, TP53, DNMT3A) were <60 years old. The most common pathogenic variants were in epigenetic regulators, DNMT3A (37.5%) & TET2 (16.7%) with a median VAF of 2.8% (range, 0.70-50%). Eight patients (47%) with pathogenic CH had grade 1 cytopenias at baseline, compared to 10 patients (50%) without pathogenic CH. One patient had grade 3/4 cytopenia at baseline & had a missense variant in TP53 (VAF 50%) & history of exposure to anthracyclines, alkylating agents, platinum & radiation. The patient developed MDS before receiving PRRT. Pathogenic CH variants were more common in patients with previous exposure to radiation (p=0.008) or SSA (p=0.005). Two patients had PPM1D variants, both with a history of prior radiation, one with a history of prior alkylating treatment. Conclusion: To our knowledge this is the largest prospective evaluation of CH in NET. We identified CH to be present in 46% of patients & DNMT3A mutations were most common. This establishes the clonal landscape with mutations involving epigenetic regulators, DNA damage repair, transcription & splicing factors. Prospective longitudinal evaluation will evaluate the association between CH, cytopenias and tMN. Citation Format: Yael Kusne, Terra Lasho, Zaid Elsabbagh, Abhishek Mangaonkar, Rachel Eiring, Timothy Hobday, Jason Starr, Tanios Bekaii-Saab, Thorvardur Halfdanarson, Mrinal Patnaik, Mohamad Sonbol. Prevalence of clonal hematopoiesis in neuroendocrine tumor patients prior to lutetium 177 dotatate therapy (Lu177): A prospective trial of 36 patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5928.

We conducted a retrospective/prospective worldwide study on patients with neuroendocrine neoplasms (NENs) and a molecularly proven SARS-CoV-2 positivity. Preliminary results regarding 85 patients of the INTENSIVE study have been published in 2021. Now we are reporting the 2-year analysis.Here, we are reporting data from consecutive patients enrolled between 1 June 2020, and 31 May 2022. Among the 118 contacted centers, 25 were active to enroll and 19 actively recruiting at the time of data cut-off for a total of 280 patients enrolled. SARS-CoV-2 positivity occurred in 47.5% of patients in 2020, 35.1% in 2021, and 17.4% in 2022. The median age for COVID-19 diagnosis was 60 years. Well-differentiated tumors, non-functioning, metastatic stage, and gastroenteropancreatic (GEP) primary sites represented most of the NENs. COVID-19-related pneumonia occurred in 22.8% of the total, with 61.3% of them requiring hospitalization; 11 patients (3.9%) needed sub-intensive or intensive care unit therapies and 14 patients died (5%), in 11 cases (3.9%) directly related to COVID-19. Diabetes mellitus and age at COVID-19 diagnosis > 70 years were significantly associated with COVID-19 mortality, whereas thoracic primary site with COVID-19 morbidity. A significant decrease in both hospitalization and pneumonia occurred in 2022 vs 2020. In our largest series of NEN patients with COVID-19, the NEN population is similar to the general population of patients with NEN regardless of COVID-19. However, older age, non-GEP primary sites and diabetes mellitus should be carefully considered for increased COVID-19 morbidity and mortality. Relevant information could be derived by integrating our results with NENs patients included in other cancer patients with COVID-19 registries.

Importance Metastatic colorectal cancer (mCRC) with deficient DNA mismatch repair (dMMR) shows frequent and durable responses to programmed cell death 1 blockade. While most of these tumors are sporadic and observed in older patients, first-line pembrolizumab data are limited to findings from the KEYNOTE-177 trial (A Phase III Study of Pembrolizumab [MK-3475] vs Chemotherapy in Microsatellite Instability-High [MSI-H] or Mismatch Repair Deficient [dMMR] Stage IV Colorectal Carcinoma). Objective To investigate outcome with first-line pembrolizumab monotherapy in mostly older patients with dMMR mCRC at a multisite clinical practice. Design, Setting, and Participants This cohort study included consecutive patients with dMMR mCRC who received pembrolizumab monotherapy between April 1, 2015, and January 1, 2022, at Mayo Clinic sites and the Mayo Clinic Health System. Patients were identified from review of electronic health records at the sites, which included the evaluation of digitized radiologic imaging studies. Intervention Patients with dMMR mCRC received first-line pembrolizumab, 200 mg, every 3 weeks. Main Outcomes and Measures The primary study end point was progression-free survival (PFS), which was analyzed using the Kaplan-Meier method and a multivariable stepwise Cox proportional hazards regression model. Clinicopathological features, including metastatic site and molecular data ( BRAF V600E and KRAS ), were also analyzed along with tumor response rate, which was determined using Response Evaluation Criteria in Solid Tumors, version 1.1. Results The study cohort included 41 patients (median [IQR] age at treatment initiation, 81 [76-86] years; 29 females [71%]) with dMMR mCRC. Of these patients, 30 (79%) had the BRAF V600E variant and 32 (80%) were classified as having sporadic tumors. Median (range) follow-up was 23 (3-89) months. Median (IQR) number of treatment cycles was 9 (4-20). Overall response rate was 49% (20 of 41 patients), including 13 patients (32%) with complete responses and 7 (17%) with partial responses. Median (IQR) PFS was 21 (95% CI, 6-39) months. Liver as a site of metastasis was associated with significantly poorer PFS vs nonliver metastasis (adjusted hazard ratio, 3.40; 95% CI, 1.27-9.13; adjusted P = .01). Complete and partial responses were observed in 3 patients (21%) with liver metastasis vs 17 patients (63%) with nonliver metastases. Treatment-related grade 3 or 4 adverse events were observed in 8 patients (20%), 2 of whom discontinued therapy; there was 1 treatment-related death. Conclusions and Relevance This cohort study found a clinically significant prolongation of survival in older patients with dMMR mCRC who were treated with first-line pembrolizumab in routine clinical practice. Furthermore, liver vs nonliver metastasis was associated with poorer survival in this patient population, which suggests that the metastatic site has implications for survival outcome.

641 Background: Tumors of neuroendocrine origin are a rare, heterogenous group of neoplasms. Neuroendocrine neoplasms (NENs) are categorized by site of origin, differentiation status, and by grade (Ki-67 expression and/or mitotic rate), with prognostic variability accordingly. These tumors frequently metastasize to bone, with reported incidence between 6-12% by older SSTR imaging. Our study evaluates patients with well-differentiated tumors of neuroendocrine origin to determine the incidence of osseous metastases when evaluated with higher-sensitivity Ga68 DOTATATE PET scans. The study characterizes the clinical features. Methods: This study was performed at a single, 3-site, US tertiary-care institution. IRB approval was obtained. An automated data extraction tool was used to mine the electronic medical record by searching all positron emission tomography (PET) studies for keywords. Identified scans had to include a combination of the following keywords: “Dotatate” AND “met*” or “lesion” AND “bone” or “osse*” or “skel*”. The individual medical records from the generated report were reviewed to include only patients with 1) well-differentiated NETs of GI and pancreatic origin, lung carcinoid, paraganglioma/pheochromocytoma, or other/unknown primary site, and 2) patients with confirmed osseous metastatic disease. Patient data was entered into a database and evaluated in aggregate. Results: 1,948 PET scans of 1,473 patients were extracted from the EMR, from which 424 patients were identified for inclusion; scans were performed between 5/2018 and 5/2021. Calculated incidence of bone metastasis by Ga68 DOTATATE PET was 28.8%. Median age of included population was 61 years (range 14-92), 49.5% being male. Site of origin was 47.2% bowel NET, 18.9% pancreatic NET, 10.8% lung carcinoid, 10.6% paraganglioma/pheochromocytoma, 2.1% other site, and 10.4% unknown primary. Majority of patients were asymptomatic (64.0%), had sclerotic appearance (76.7%), Krenning 4 (71.4%), and >3 sites (68.3%) of osseous disease. 94.6% of the population had disease of the axial skeleton; 65.6% appendicular. Only 57 patients (13.4%) with osseous disease suffered a fracture, despite metastases at high-risk sites. Fracture occurred at disproportionately low rates in NETs originating in bowel (22.8% of fractures), with proportionately higher rates among pancreatic NETS and paragangliomas/pheochromocytomas (31.6% and 22.8%, respectively). Fractures occurred at proportionately higher rates in higher-grade disease compared to low-grade. Conclusions: Osseous metastatic disease in well-differentiated NENs is evident at much higher rates when imaging with Ga68 DOTATATE PET compared with previously reported data. Nevertheless, fracture occurred at a low rate, suggesting that these patients are at a relatively low risk for skeletal-related events.

Abstract Background Despite multiple randomized trials, the role of perioperative chemotherapy in colorectal cancer liver metastasis (CRLM) is still under debate. In this systematic review and network meta-analysis (NMA), we aim to evaluate the efficacy of perioperative systemic therapies for patients with CRLM. Methods We searched various databases for abstracts and full-text articles published from database inception through May 2021.We included randomized controlled trials (RCTs) comparing the addition of perioperative (post, pre, or both) systemic therapies to surgery alone in patients with CRLM. The outcomes were compared according to the chemotherapy regimen using a random effects model. Outcomes of interest included disease-free survival (DFS) and overall survival (OS). Results Seven RCTs with a total of 1504 patients with CRLM were included. Six studies included post-operative treatment and one evaluated perioperative (pre- and postoperative) therapy. Fluoropyrimidine-based chemotherapy was the most used systemic therapy. NMA showed benefit of adding perioperative therapy to surgery in terms of DFS (HR 0.73, 95% CI 0.63 to 0.84). However, these findings did not translate into a statistically significant OS benefit (HR 0.88, 95% CI 0.74 to 1.05). NMA did not show any advantage of one regimen over another including oxaliplatin or irinotecan. Conclusions This systematic review and NMA of 7 RCTs found that the addition of perioperative systemic treatment for resectable CRLM could improve disease-free survival but not overall survival. Based on the findings, addition of perioperative treatment in resectable CRLM should be individualized weighing the risks and benefits.

Abstract Background: Sarcopenia is one of the early pathological features of cancer cachexia, yet the effect of sarcopenia on clinical outcomes in patients with advanced HCC is unclear. Our objective was to determine the effect of Sarcopenia on response to systemic therapy with advanced HCC. Methods: Patients with unresectable and advanced liver cancer were retrospectively evaluated between 2010 to 2019. Skeletal muscle area (SMA) was computed with a previously validated computed tomography (CT) body composition AI algorithm. The skeletal muscle index (SMI) was derived from the skeletal muscle area (SMA) (cm2) divided by patient height (m2) calculated from images at the level of L3 on pretreatment CT. Sarcopenia cutoffs for females was less than 39 cm2/m2 SMI or less than 50 cm2/m2 SMI for males. Patients’ demographics, systemic treatment response, toxicity, progression-free survival (PFS) and overall survival (OS) were compared between first-line therapy groups. Kaplan-Meier and Cox proportional hazards regression were used for survival analysis comparisons. Results: A total of 146 patients with advanced HCC were assessed from Mayo Clinic Arizona and Emory University. Seventy-six patients received immunotherapy as first-line treatment and seventy patients received TKI as first-line therapy. Sarcopenia at baseline was assessed in a total of 91 patients at first-line systemic treatment: n=48 with immunotherapy (IO) and n=43 with tyrosine kinase inhibitor (TKI). Sarcopenia was more prevalent in male patients (p=0.009), and in patients with low BMI (p=0.02). When comparing those with sarcopenia at baseline, higher response rate was observed in patients treated with IO without sarcopenia (47% versus 15%, p=0.019), this was not observed in TKI group. Interestingly, median PFS and OS was not significantly changed in patients with or without sarcopenia treated with IO or TKI on first-line therapy. Conclusions: Sarcopenia was associated with reduced response rate (RR) in patients treated with IO, but not in TKI groups. Both didn’t translate into deleterious effect in PFS and or OS. Further research with sufficient adjustments for confounding factors is warranted to better elucidate the prognostic value of sarcopenia in these patients. Citation Format: Gehan Botrus, Pedro Luiz Serrano Uson Junior, Heidi Kosiorek, Mehmet Akce, Isabela Chang, Zhubene Mesbah, Eric Yancey, Daniel Blezek, Jason Klug, Lana Khalil, Puneet Raman, Mohamad Sonbol, Mitesh Borad, Daniel Ahn, Tanios Bekaii-Saab. Prognostic impact of Sarcopenia on clinical outcomes in advanced hepatocellular carcinoma (HCC) treated with systemic therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6274.