Overman, Michael J.

This selection from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Colon Cancer focuses on systemic therapy options for the treatment of metastatic colorectal cancer (mCRC), because important updates have recently been made to this section. These updates include recommendations for first-line use of checkpoint inhibitors for mCRC, that is deficient mismatch repair/microsatellite instability-high, recommendations related to the use of biosimilars, and expanded recommendations for biomarker testing. The systemic therapy recommendations now include targeted therapy options for patients with mCRC that is HER2-amplified, or BRAF V600E mutation–positive. Treatment and management of nonmetastatic or resectable/ablatable metastatic disease are discussed in the complete version of the NCCN Guidelines for Colon Cancer available at NCCN.org . Additional topics covered in the complete version include risk assessment, staging, pathology, posttreatment surveillance, and survivorship.

Abstract Immunotherapy targeting immune checkpoints has become a common approach for many types of cancer but currently there are no reliable biomarkers to predict and monitor treatment response. Immunohistochemical staining of PD-L1, which was initially developed as a companion diagnostic, is problematic due to tumor heterogeneity, variations in specimen preparation and multiple scoring schemes. There is, therefore, a critical need for a better biomarker to guide the use of immunotherapy to improve clinical outcomes. We previously reported that higher levels of Bim and CX3CR1/granzyme B in CD8+ T cells were associated with increased response to PD-1 blockade therapy in patients with melanoma; high levels of Bim were also prognostic of poor survival in melanoma patients. In this study, we investigated the roles of Bim and CX3CR1/granzyme B in patients receiving PD-1 blockade therapy (i.e. pembrolizumab) for small bowel adenocarcinoma as part of planned correlative analysis of the ACCRU clinical trial, NCT02949219. Patients with unresectable or metastatic biopsy-proven small bowel adenocarcinoma (excluding ampulla of Vater and appendix) who had at least one prior line of systemic chemotherapy were eligible for the trial. Pembrolizumab (200 mg) was administered over 30 minutes intravenously every 3 weeks until unacceptable toxicity, disease progression, or patient refusal. All patients underwent peripheral blood collection at baseline prior to initiation of treatment and then after 3 cycles of treatment. Levels of Bim and CX3CR1/granzyme B in circulating T cells were quantified by flow cytometry using patients' peripheral blood mononuclear cells. Data was analyzed via Cox proportional hazards model, Wilcoxon Rank-Sum test, and Kaplan Meier curves using SAS 9.4. A total of 35 eligible patients were included in the analysis. Three patients had confirmed response (all partial responses) and 10 had stable disease as their best overall response. Seven patients had disease progression around the second blood draw. The median time from baseline to the second blood draw was 9 weeks. Lower levels of Bim in CD8+CD11ahi T cells at baseline on the percentage scale were associated with treatment response (median 54.5% vs. 79.5%; p=0.0087) and disease control (partial response plus stable disease; median 71.2% vs. 81.3%; p=0.0104) but higher levels led to worse progression-free survival (hazard ratio=1.05, 95% confidence interval 1.01-1.08; p=0.0051). In addition, positive changes in CX3CR1/granzyme B in CD8+CD11ahi T cells from baseline were associated with better overall survival (median 20.2 months vs. 3.7 months, p=0.0086). The levels of PD-1 and Ki-67 in CD8+CD11ahi T cells were not associated with treatment response or survival. In conclusion, Bim and CX3CR1/granzyme B are biomarkers that associate with response and survival benefits respectively of PD-1 blockade therapy. This preliminary data calls for a larger-scale, prospective study to validate their predictive and prognostic utilities. Citation Format: Mojun Zhu, Henan Zhang, Nathan R. Foster, Haidong Dong, Tanios S. Bekaii-Saab, Brandy L. Jaszewski, Patrick M. Boland, Michael J. Overman, Katrina Pedersen, Robert R. McWilliams, Academic and Community Cancer Research United (AACRU). Bim and CX3CR1/granzyme B in circulating CD8+ T cells are predictive biomarkers for PD-1 blockade therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4467.

The NCCN Guidelines for Rectal Cancer provide recommendations for the diagnosis, evaluation, treatment, and follow-up of patients with rectal cancer. These NCCN Guidelines Insights summarize the panel discussion behind recent important updates to the guidelines. These updates include clarifying the definition of rectum and differentiating the rectum from the sigmoid colon; the total neoadjuvant therapy approach for localized rectal cancer; and biomarker-targeted therapy for metastatic colorectal cancer, with a focus on new treatment options for patients with BRAF V600E– or HER2 amplification–positive disease.

4047 Background: BRAFV600E mutations occur in fewer than 10% of all patients (pts) with metastatic colorectal cancer (mCRC) and arise from sessile serrated adenomas. Despite efficacy with targeted therapies against MAPK signaling and with immunotherapies in this population, survival outcomes for pts with BRAFV600E mCRC in general are poor. Characteristics distinguishing pts with BRAFV600E mCRC with favorable versus unfavorable outcomes have not been well annotated. Methods: Records of 188 pts with BRAFV600E mCRC evaluated at MD Anderson Cancer Center between 3/2010-1/2020 were reviewed. Pts with the shortest and longest metastatic survival (N = 25 for each group) were compared. Associations between prognostic group and clinical/pathologic features were measured by odds ratio and for median survival by log-rank testing. Results: Median metastatic survival differed between the 2 BRAFV600E mCRC populations (8.6 vs 84 months, p < .0001). Pts with poor survival more commonly had primary tumors arising from the hepatic flexure/proximal transverse colon (44% vs 16%, p = .04) and more frequent hepatic involvement (75% vs 28%, p = .001). Pts with favorable survival were more likely to develop metachronous metastases (52% vs 16%, p = .01), have fewer distant organ involvement (median 1 vs 2, p = .02), and undergo definitive locoregional therapy to metastatic disease (44% vs 0%, p = .01). Microsatellite instability (36% vs 4%, p = .008) and a history of tobacco use (44% vs 16%, p = .04) were associated with a favorable prognosis. Durable responses to MAPK-targeted therapies (5/25) and immunotherapy (3/25) were noted in the favorable group. Conclusions: Pts with BRAFV600E mCRC can achieve excellent long-term survival which belies conventional context and is driven by locoregional and systemic treatment options alike. Anatomic localization of the primary tumor and prior exposures may highlight environmental influences on tumor biology which account for the clinical heterogeneity of pts with BRAFV600E mCRC.

Abstract Background Carcinoembryonic antigen (CEA) levels are used in conjunction with imaging to monitor response to systemic therapy in metastatic colorectal cancer (mCRC). We sought to identify a threshold for CEA change from baseline to predict progressive disease (PD) in mCRC patients receiving first-line therapy. Methods Patients from trials collected in the ARCAD database were included if baseline CEA was at least 10 ng/mL and repeat CEA was available within 14 days of first restaging scan. Optimal cutoffs for CEA change were identified by receiver operating characteristic analysis. Prediction performance of cutoffs was evaluated by sensitivity, specificity, and negative predictive value. Analyses were conducted by treatment class: chemotherapy alone, chemotherapy with anti-VEGF antibody, and chemotherapy with anti-EGFR antibody. Results A total of 2643 mCRC patients treated with systemic therapy were included. Median percent change of CEA from baseline to first restaging for patients with complete response, partial response, or stable disease (non-PD) and PD was −53.1% and +23.6% for chemotherapy alone (n = 957) and −71.7% and −45.3% for chemotherapy with anti-VEGF antibody (n = 1355). The optimal area under the curve cutoff for differentiating PD from non-PD on first restaging was −7.5% for chemotherapy alone and −62.0% for chemotherapy with anti-VEGF antibody; chemotherapy alone, adjusted odds ratio = 6.51 (95% CI = 3.31 to 12.83, P &lt; .001), chemotherapy with anti-VEGF antibody, adjusted odds ratio = 3.45 (95% CI = 1.93 to 6.18, P &lt; .001). A 99% negative predictive value clinical cutoff for prediction of non-PD would avoid CT scan at first restaging in 21.0% of chemotherapy alone and 16.2% of chemotherapy with anti-VEGF antibody–treated patients. Among patients with stable disease on first restaging, those with decreased CEA from baseline had statistically significantly improved progression-free and overall survival. Conclusions Change in CEA from baseline to first restaging can accurately predict non-progression and correlates with long-term outcomes in patients receiving systemic chemotherapy.

Small bowel adenocarcinoma (SBA) is a rare malignancy of the gastrointestinal tract that has increased in incidence across recent years. Often diagnosed at an advanced stage, outcomes for SBA are worse on average than for other related malignancies, including colorectal cancer. Due to the rarity of this disease, few studies have been done to direct optimal treatment, although recent data have shown that SBA responds to treatment differently than colorectal cancer, necessitating a separate approach to treatment. The NCCN Guidelines for Small Bowel Adenocarcinoma were created to establish an evidence-based standard of care for patients with SBA. These guidelines provide recommendations on the workup of suspected SBA, primary treatment options, adjuvant treatment, surveillance, and systemic therapy for metastatic disease. Additionally, principles of imaging and endoscopy, pathologic review, surgery, radiation therapy, and survivorship are described.

e15055 Background: An increasing number of pt and tumor c have predictive and prognostic implications in mCRC. However, there is no consensus on their reporting in trial results. Methods: Pt c and SF from 136 phase III trials of systemic therapies (Rx) in mCRC published between 1988 and 2018 (68,326 pts) were collected. Trials were also grouped per publication date (G1: 1988-97; G2: 98 – 2007; G3: 08-18). Patterns of reporting and trends across G were evaluated. Results: Pt c consistently reported were performance status, PS (98.5%), age (92.6%) and gender (90.4%); race (20.6%) & weight/BMI/BSA were not (13.2%). Tumor c frequently reported were metastatic (met) spread (70.6%) while time intervals related to disease course (25%) and synchronous met vs not (19.1%) were omitted. Of note, primary site was largely reported as colon vs rectum (69%) and sidedness or anatomical location was discernable only in 10.3%. Prior Rx reporting focused on chemo (58.5%) with radiation and surgery and reported in 34% & 28.7%. Reporting of prognostic factors was variable and limited: histology grade CEA, alk phos, LDH (range 10.3-15.4%). Only 11.8% of trials reported genomic factors - KRAS MT was included in all with BRAF MT in 4.4%. Of 140 trials used for SF analysis, 115 had ≥ 1 (range 1-7). Common SF were PS (60%), geography /institution (55.7%). Prior Rx (27%), met spread (24.3%) were sometimes used while primary site (7.8%), genomic factors (6.1%) rarely were. Trends across G are per Table. Conclusions: There is marked inconsistency in pt c & SF reporting in mCRC trials. Consensus guidelines will aid in standardization of trial interpretation and future meta-analyses; and will need to be updated based on emerging data. [Table: see text]

656 Background: Despite multiple trials of new agents in metastatic colorectal cancer (mCRC), long term outcomes remain poor. This study explores the changing trends in the design, interpretation and outcomes of phase III randomized controlled trials (RCT) in mCRC over time. Methods: Phase III RCTs of systemic therapy for mCRC with enrollment between 1986 and 2016 were identified through 4 electronic databases and grouped into 3 time periods (1986-1996 – T1; 1997-2006 – T2 & 2007-2016 – T3). Study selection, quality appraisal and data collection were performed by 2 independent investigators. Study characteristics, primary and secondary endpoints, and authors’ interpretation of results and conclusions were analyzed. Improvement in overall survival (OS) was the difference between experimental and control arms. A study was deemed positive if it met its end point, was recommended for further study or for adoption for clinical use (p ≤ 0.05 significant for all analyses). Results: One hundred fifty trials (T1=36, T2=62, T3=52) with 77494 patients (T1=12406, T2=39158, T3=25930) were included. Although 1st line therapy trials continued to be the most common across all T, the percentage (%) of trials evaluating 3rd line and beyond (T1=0, T2=3, T3=27) have increased significantly over time as have trials with targeted agents (T1=11, T2=34, T3=79). Although OS remains the most common primary end point, more trials in T2 & T3 have used progression-free survival instead (14 vs 47 & 44). The % of trials with negative results but interpreted as positive increased over time (T1=18; T2=42; T3=35). Across all T, the median improvement in OS (months, m) of these trials was significantly lower compared to the trials that met primary end point across all T (T1 = 0 vs 1.8 m, T2 = -0.1 vs 3.25, T3 = -0.25 vs 2.55). Conclusions: A significant shift has occurred over the past three decades in the design and interpretation of phase III trials in advanced CRC. Any interpretations of potential survival benefits from trials that have not met primary end point must be made with significant caution.

TPS535 Background: Small bowel adenocarcinoma (SBA) is a rare malignancy, possibly because of the high rate of immunosurveillance in baseline small bowel function, and is frequently diagnosed in late stages. Due to these factors, there is no consistent standard of care for metastatic disease beyond first-line where several prospective studies have confirmed activity of FOLFOX/CAPOX. Historically, second-line treatment of SBA has been extrapolated from colon/gastric cancer. Recent studies suggest that SBA has a distinct genomic profile, including higher incidence of microsatellite instability, compared to gastric and colon cancers. Additionally, the tumor microenvironment reflects a greater degree of PD-L1 expression and infiltration by lymphocytes. Immune checkpoint inhibitors have not previously been tested in SBA unselected for MSI status. Methods: The study is a phase 2, multicenter, single-arm clinical trial of pembrolizumab (200 mg IV every 3 weeks) for patients with unresectable or metastatic SBA refractory to first-line chemotherapy. Forty patients with any tumor mismatch repair status will be enrolled at 8 US sites as part of the ACCRU network and International Rare Cancer Initiative (IRCI) with a primary objective to assess the confirmed response rate (H0 p < 10%, HA: p > 30%) to pembrolizumab. Secondary endpoints include PFS, OS, and adverse events. Correlative aims include assessing blood and tissue biomarkers (i.e. PD-L1, MSI-H/MSS status, cfDNA, mutation burden, etc.) for association with clinical benefit. An interim analysis will be performed to assess efficacy after 18 patients become evaluable. The study is open with 16 patients enrolled at time of submission. Clinical trial information: NCT02949219.