Immune checkpoint inhibitors for POLE or POLD1 proofreading-deficient metastatic colorectal cancer.

BACKGROUND: POLE and POLD1 proofreading deficiency (POLE/D1pd) define a rare subtype of ultramutated metastatic colorectal cancer (mCRC; over 100 mut/Mb). Disease-specific data about the activity and efficacy of immune checkpoint inhibitors (ICIs) in POLE/D1pd mCRC are lacking and it is unknown whether outcomes may be different from mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) mCRCs treated with ICIs. PATIENTS AND METHODS: In this global study, we collected 27 patients with mCRC harboring POLE/D1 mutations leading to proofreading deficiency and treated with anti-programmed cell death-ligand 1 alone +/- anti-cytotoxic T-lymphocyte antigen-4 agents. We collected clinicopathological and genomic characteristics, response, and survival outcomes after ICIs of POLE/D1pd mCRC and compared them with a cohort of 610 dMMR/MSI-H mCRC patients treated with ICIs. Further genomic analyses were carried out in an independent cohort of 7241 CRCs to define POLE and POLD1pd molecular profiles and mutational signatures. RESULTS: POLE/D1pd was associated with younger age, male sex, fewer RAS/BRAF driver mutations, and predominance of right-sided colon cancers. Patients with POLE/D1pd mCRC showed a significantly higher overall response rate (ORR) compared to dMMR/MSI-H mCRC (89% versus 54%; P = 0.01). After a median follow-up of 24.9 months (interquartile range: 11.3-43.0 months), patients with POLE/D1pd showed a significantly superior progression-free survival (PFS) compared to dMMR/MSI-H mCRC [hazard ratio (HR) = 0.24, 95% confidence interval (CI) 0.08-0.74, P = 0.01] and superior overall survival (OS) (HR = 0.38, 95% CI 0.12-1.18, P = 0.09). In multivariable analyses including the type of DNA repair defect, POLE/D1pd was associated with significantly improved PFS (HR = 0.17, 95% CI 0.04-0.69, P = 0.013) and OS (HR = 0.24, 95% CI 0.06-0.98, P = 0.047). Molecular profiling showed that POLE/D1pd tumors have higher tumor mutational burden (TMB). Responses were observed in both subtypes and were associated with the intensity of POLE/D1pd signature. CONCLUSIONS: Patients with POLE/D1pd mCRC showed more favorable outcomes compared to dMMR/MSI-H mCRC to treatment with ICIs in terms of tumor response and survival.

Nivolumab plus low-dose ipilimumab in previously treated patients with microsatellite instability-high/mismatch repair-deficient metastatic colorectal cancer: 4-year follow-up from CheckMate 142.

BACKGROUND: In the phase II multicohort CheckMate 142 study, nivolumab plus low-dose (1 mg/kg) ipilimumab provided robust and durable clinical benefit with a manageable safety profile in previously treated patients with microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC) at 13.4- and 25.4-month median follow-up (Overman MJ, Lonardi S, Wong KYM et al. Durable clinical benefit with nivolumab plus ipilimumab in DNA mismatch repair-deficient/microsatellite instability-high metastatic colorectal cancer. J Clin Oncol. 2018;36:773-779. Overman MJ, Lonardi S, Wong KYM, et al. Nivolumab plus low-dose ipilimumab in previously treated patients with microsatellite instability-high/mismatch repair deficient metastatic colorectal cancer: long-term follow-up. J Clin Oncol. 2019;37:635). Here, we present results from the 4-year follow-up of these patients. PATIENTS AND METHODS: Patients received nivolumab (3 mg/kg) plus low-dose (1 mg/kg) ipilimumab every 3 weeks (four doses) followed by nivolumab (3 mg/kg) every 2 weeks until disease progression. Primary endpoint was investigator-assessed objective response rate (ORR; as per RECIST version 1.1). RESULTS: A total of 119 patients were treated; 76% had ≥2 prior lines of therapy. Median follow-up was 50.9 months (range 46.9-62.7 months). Median duration of therapy was 24.9 months [95% confidence interval (CI) 15.8-33.2 months]. Investigator-assessed ORR increased from 55% (95% CI 45% to 64%) at 13.4 months to 65% (95% CI 55% to 73%) at 50.9 months with a disease control rate of 81% (95% CI 72% to 87%). The complete response rate increased from 3% at 13.4 months to 13% at 50.9 months. Partial responses were observed in 52% of patients; 21% had stable disease, and 12% had progressive disease. Median time to response was 2.8 months (range 1.1-37.1 months), and median duration of response was not reached (range 1.4+ to 58.0+ months). At data cut-off, 37 (48%) patients had ongoing responses. Median progression-free survival was not reached [95% CI 38.4 months-not estimable (NE)], and median overall survival was not reached (95% CI NE). Grade 3-4 treatment-related adverse events (TRAEs) were observed in 32% of patients; 13% of patients had any-grade TRAEs leading to discontinuation. CONCLUSIONS: The results confirm long-term benefit of nivolumab plus low-dose ipilimumab for previously treated patients with MSI-H/dMMR mCRC. The safety profile was manageable with no new safety signals.

Metastatic small bowel adenocarcinoma: role of metastasectomy and systemic chemotherapy.

BACKGROUND: Metastatic small bowel adenocarcinoma (SBA) has a poor prognosis. Due to its rarity, high-quality data are lacking to guide treatment. This retrospective analysis was conducted to help characterize the treatment options for patients with metastatic SBA while providing clinically meaningful prognostic information. PATIENTS AND METHODS: In total, 437 patients who initially presented with or developed metastatic SBA between September 1977 and September 2019 were identified from the MD Anderson Tumor Registry. Clinical data were collected from review of the medical record. Overall response rates (ORR), time to progression (TTP), and overall survival (OS) were assessed across various treatments and treatment lines. RESULTS: The median OS from diagnosis of metastatic disease was 15.9 months [95% confidence interval (CI): 14.3-17.9]. Seventy-five patients (17.1%) underwent metastasectomy, which was associated with a median OS of 34.5 versus 17.1 months among patients who received chemotherapy alone (P < 0.001). Fluoropyrimidine plus platinum (n = 164) was the most common first-line chemotherapy, associated with an ORR of 59% and TTP of 8.1 months. Irinotecan with 5-FU (n = 101) was the most common second-line therapy associated with an ORR of 31% and TTP of 4.0 months. Twenty-two patients received immunotherapy; 5 of 6 patients with deficient mismatch repair (dMMR) responded, while 0 of 16 with proficient mismatch repair (pMMR) responded. Taxane-based chemotherapy was given to 34 patients with an ORR of 21% and a median TTP of 2.4 months. Among 11 patients who received anti-epidermal-growth-factor-receptor (EGFR) monotherapy, the best response was stable disease (SD) in 1 patient. CONCLUSIONS: In well-selected patients with SBA, metastasectomy appears to be associated with improved OS. This improvement was seen across metastasectomy sites, including liver, lung and peritoneal. Anti-programmed cell death protein 1 (PD-1) based immunotherapy was active for dMMR SBA but not pMMR SBA. While taxane-based chemotherapy demonstrates therapeutic activity, the activity of anti-EGFR therapy was limited.

JSCO-ESMO-ASCO-JSMO-TOS: international expert consensus recommendations for tumour-agnostic treatments in patients with solid tumours with microsatellite instability or NTRK fusions.

A Japan Society of Clinical Oncology (JSCO)-hosted expert meeting was held in Japan on 27 October 2019, which comprised experts from the JSCO, the Japanese Society of Medical Oncology (JSMO), the European Society for Medical Oncology (ESMO), the American Society of Clinical Oncology (ASCO), and the Taiwan Oncology Society (TOS). The purpose of the meeting was to focus on what we have learnt from both microsatellite instability (MSI)/deficient mismatch repair (dMMR) biomarkers in predicting the efficacy of anti-programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1) immunotherapy, and the neurotrophic tyrosine receptor kinase (NTRK) gene fusions in predicting the efficacy of inhibitors of the tropomyosin receptor kinase (TRK) proteins across a range of solid tumour types. The recent regulatory approvals of the anti-PD-1 antibody pembrolizumab and the TRK inhibitors larotrectinib and entrectinib, based on specific tumour biomarkers rather than specific tumour type, have heralded a paradigm shift in cancer treatment approaches. The purpose of the meeting was to develop international expert consensus recommendations on the use of such tumour-agnostic treatments in patients with solid tumours. The aim was to generate a reference document for clinical practice, for pharmaceutical companies in the design of clinical trials, for ethics committees in the approval of clinical trial protocols and for regulatory authorities in relation to drug approvals, with a particular emphasis on diagnostic testing and patient selection.

Anti-EGFR-resistant clones decay exponentially after progression: implications for anti-EGFR re-challenge.

BACKGROUND: Colorectal cancer (CRC) has been shown to acquire RAS and EGFR ectodomain mutations as mechanisms of resistance to epidermal growth factor receptor (EGFR) inhibition (anti-EGFR). After anti-EGFR withdrawal, RAS and EGFR mutant clones lack a growth advantage relative to other clones and decay; however, the kinetics of decay remain unclear. We sought to determine the kinetics of acquired RAS/EGFR mutations after discontinuation of anti-EGFR therapy. PATIENTS AND METHODS: We present the post-progression circulating tumor DNA (ctDNA) profiles of 135 patients with RAS/BRAF wild-type metastatic CRC treated with anti-EGFR who acquired RAS and/or EGFR mutations during therapy. Our validation cohort consisted of an external dataset of 73 patients with a ctDNA profile suggestive of prior anti-EGFR exposure and serial sampling. A separate retrospective cohort of 80 patients was used to evaluate overall response rate and progression free survival during re-challenge therapies. RESULTS: Our analysis showed that RAS and EGFR relative mutant allele frequency decays exponentially (r2=0.93 for RAS; r2=0.94 for EGFR) with a cumulative half-life of 4.4 months. We validated our findings using an external dataset of 73 patients with a ctDNA profile suggestive of prior anti-EGFR exposure and serial sampling, confirming exponential decay with an estimated half-life of 4.3 months. A separate retrospective cohort of 80 patients showed that patients had a higher overall response rate during re-challenge therapies after increasing time intervals, as predicted by our model. CONCLUSION: These results provide scientific support for anti-EGFR re-challenge and guide the optimal timing of re-challenge initiation.

Phase II study of nab-paclitaxel in refractory small bowel adenocarcinoma and CpG island methylator phenotype (CIMP)-high colorectal cancer.

Background: Hypermethylation of promoter CpG islands [CpG island methylator phenotype (CIMP)] represents a unique pathway for the development of colorectal cancer (CRC), characterized by lack of chromosomal instability and a low rate of adenomatous polyposis coli (APC) mutations, which have both been correlated with taxane resistance. Similarly, small bowel adenocarcinoma (SBA), a rare tumor, also has a low rate of APC mutations. This phase II study evaluated taxane sensitivity in SBA and CIMP-high CRC. Patients and methods: The primary objective was Response Evaluation Criteria in Solid Tumors version 1.1 response rate. Eligibility included Eastern Cooperative Oncology Group performance status 0/1, refractory disease, and SBA or CIMP-high metastatic CRC. Nab-paclitaxel was initially administered at a dose of 260 mg/m2 every 3 weeks but was reduced to 220 mg/m2 owing to toxicity. Results: A total of 21 patients with CIMP-high CRC and 13 with SBA were enrolled from November 2012 to October 2014. The efficacy-assessable population (patients who received at least three doses of the treatment) comprised 15 CIMP-high CRC patients and 10 SBA patients. Common grade 3 or 4 toxicities were fatigue (12%), neutropenia (9%), febrile neutropenia (9%), dehydration (6%), and thrombocytopenia (6%). No responses were seen in the CIMP-high CRC cohort and two partial responses were seen in the SBA cohort. Median progression-free survival was significantly greater in the SBA cohort than in the CIMP-high CRC cohort (3.2 months compared with 2.1 months, P = 0.03). Neither APC mutation status nor CHFR methylation status correlated with efficacy in the CIMP-high CRC cohort. In vivo testing of paclitaxel in an SBA patient-derived xenograft validated the activity of taxanes in this disease type. Conclusion: Although preclinical studies suggested taxane sensitivity was associated with chromosomal stability and wild-type APC, we found that nab-paclitaxel was inactive in CIMP-high metastatic CRC. Nab-paclitaxel may represent a novel therapeutic option for SBA.

High prevalence of mutant KRAS in circulating exosome-derived DNA from early-stage pancreatic cancer patients.

Background: Exosomes arise from viable cancer cells and may reflect a different biology than circulating cell-free DNA (cfDNA) shed from dying tissues. We compare exosome-derived DNA (exoDNA) to cfDNA in liquid biopsies of patients with pancreatic ductal adenocarcinoma (PDAC). Patients and methods: Patient samples were obtained between 2003 and 2010, with clinically annotated follow up to 2015. Droplet digital PCR was performed on exoDNA and cfDNA for sensitive detection of KRAS mutants at codons 12/13. A cumulative series of 263 individuals were studied, including a discovery cohort of 142 individuals: 68 PDAC patients of all stages; 20 PDAC patients initially staged with localized disease, with blood drawn after resection for curative intent; and 54 age-matched healthy controls. A validation cohort of 121 individuals (39 cancer patients and 82 healthy controls) was studied to validate KRAS detection rates in early-stage PDAC patients. Primary outcome was circulating KRAS status as detected by droplet digital PCR. Secondary outcomes were disease-free and overall survival. Results: KRAS mutations in exoDNA, were identified in 7.4%, 66.7%, 80%, and 85% of age-matched controls, localized, locally advanced, and metastatic PDAC patients, respectively. Comparatively, mutant KRAS cfDNA was detected in 14.8%, 45.5%, 30.8%, and 57.9% of these individuals. Higher exoKRAS MAFs were associated with decreased disease-free survival in patients with localized disease. In the validation cohort, mutant KRAS exoDNA was detected in 43.6% of early-stage PDAC patients and 20% of healthy controls. Conclusions: Exosomes are a distinct source of tumor DNA that may be complementary to other liquid biopsy DNA sources. A higher percentage of patients with localized PDAC exhibited detectable KRAS mutations in exoDNA than previously reported for cfDNA. A substantial minority of healthy samples demonstrated mutant KRAS in circulation, dictating careful consideration and application of liquid biopsy findings, which may limit its utility as a broad cancer-screening method.

Prognostic factors after resection of colorectal liver metastases following preoperative second-line chemotherapy: Impact of RAS mutations.

BACKGROUND: After resection of colorectal liver metastases (CLM), RAS mutations are associated with modest survival benefit and second-line chemotherapy confers limited hope for cure. OBJECTIVE: To evaluate the impact of RAS mutation after second-line chemotherapy for patients undergoing potentially curative liver resection for CLM. METHODS: Among 1357 patients operated for CLM between January 2005 and November 2014, patients with known RAS mutational status were identified. Outcomes after second-line chemotherapy were analyzed by RAS status. RESULTS: Among 635 patients undergoing resection of CLM, 46 received second-line chemotherapy before resection, including 14 patients (30%) with RAS mutations. Patients who received second-line chemotherapy had significantly larger and greater number of liver metastases and were more likely to undergo major hepatectomy. Median overall (OS) and recurrence free survival (RFS) were significantly worse among patients requiring second-line chemotherapy (OS: 44.4 vs. 61.1 months, p = 0.021; RFS: 7.3 vs. 12.0 months, p = 0.001). Among patients undergoing liver resection after second-line chemotherapy, RAS mutations were associated with worse median OS and RFS (OS: 35.2 vs. 60.7 months, p = 0.038; RFS: 3.6 vs. 8.3 months, p = 0.015). RAS mutation was the only independent factor associated with OS and RFS. All patients with RAS mutations recurred within 18 months. Among patients with RAS wild-type tumors, the receipt of second-line chemotherapy did not affect OS (p = 0.493). CONCLUSION: Among patients undergoing resection of CLM after second-line chemotherapy, RAS mutational status is an independent predictor of survival and outweighs other factors to select patients for liver resection.

Utility of a molecular prescreening program in advanced colorectal cancer for enrollment on biomarker-selected clinical trials.

BACKGROUND: Incorporation of multiple enrichment biomarkers into prospective clinical trials is an active area of investigation, but the factors that determine clinical trial enrollment following a molecular prescreening program have not been assessed. PATIENTS AND METHODS: Patients with 5-fluorouracil-refractory metastatic colorectal cancer at the MD Anderson Cancer Center were offered screening in the Assessment of Targeted Therapies Against Colorectal Cancer (ATTACC) program to identify eligibility for companion phase I or II clinical trials with a therapy targeted to an aberration detected in the patient, based on testing by immunohistochemistry, targeted gene sequencing panels, and CpG island methylation phenotype assays. RESULTS: Between August 2010 and December 2013, 484 patients were enrolled, 458 (95%) had a biomarker result, and 157 (32%) were enrolled on a clinical trial (92 on biomarker-selected and 65 on nonbiomarker selected). Of the 458 patients with a biomarker result, enrollment on biomarker-selected clinical trials was ninefold higher for predefined ATTACC-companion clinical trials as opposed to nonpredefined biomarker-selected clinical trials, 17.9% versus 2%, P < 0.001. Factors that correlated positively with trial enrollment in multivariate analysis were higher performance status, older age, lack of standard of care therapy, established patient at MD Anderson, and the presence of an eligible biomarker for an ATTACC-companion study. Early molecular screening did result in a higher rate of patients with remaining standard of care therapy enrolling on ATTACC-companion clinical trials, 45.1%, in contrast to nonpredefined clinical trials, 22.7%; odds ratio 3.1, P = 0.002. CONCLUSIONS: Though early molecular prescreening for predefined clinical trials resulted in an increase rate of trial enrollment of nonrefractory patients, the majority of patients enrolled on clinical trials were refractory to standard of care therapy. Within molecular prescreening programs, tailoring screening for preidentified and open clinical trials, temporally linking screening to treatment and optimizing both patient and physician engagement are efforts likely to improve enrollment on biomarker-selected clinical trials. CLINICAL TRIALS NUMBER: The study NCT number is NCT01196130.

Retreatment with anti-EGFR based therapies in metastatic colorectal cancer: impact of intervening time interval and prior anti-EGFR response.

BACKGROUND: This retrospective study aims to investigate the activity of retreatment with anti-EGFR-based therapies in order to explore the concept of clonal evolution by evaluating the impact of prior activity and intervening time interval. METHODS: Eighty-nine KRAS exon 2-wild-type metastatic colorectal patients were retreated on phase I/II clinical trials containing anti-EGFR therapies after progressing on prior cetuximab or panitumumab. Response on prior anti-EGFR therapy was defined retrospectively per physician-records as response or stable disease ≥6 months. Multivariable statistical methods included a multiple logistic regression model for response, and Cox proportional hazards model for progression-free survival. RESULTS: Retreatment anti-EGFR agents were cetuximab (n = 76) or cetuximab plus erlotinib (n = 13). The median interval time between prior and retreatment regimens was 4.57 months (range: 0.46-58.7). Patients who responded to the prior cetuximab or panitumumab were more likely to obtain clinical benefit to the retreatment compared to the non-responders in both univariate (p = 0.007) and multivariate analyses (OR: 3.38, 95 % CI: 1.27, 9.31, p = 0.019). The clinical benefit rate on retreatment also showed a marginally significant association with interval time between the two anti-EGFR based therapies (p = 0.053). Median progression-free survival on retreatment was increased in prior responders (4.9 months, 95 % CI: 3.6, 6.2) compared to prior non-responders (2.5 months, 95 % CI, 1.58, 3.42) in univariate (p = 0.064) and multivariate analysis (HR: 0.70, 95 % CI: 0.43-1.15, p = 0.156). CONCLUSION: Our data lends support to the concept of clonal evolution, though the clinical impact appears less robust than previously reported. Further work to determine which patients benefit from retreatment post progression is needed.

Phase II study of saracatinib (AZD0530) in patients with previously treated metastatic colorectal cancer.

BACKGROUND: Src has a critical role in tumor cell migration and invasion. Increased Src activity has been shown to correlate with disease progression and poor prognosis, suggesting Src could serve as a therapeutic target for kinase inhibition. Saracatinib (AZD0530) is a novel selective oral Src kinase inhibitor. METHODS: Metastatic colorectal cancer patients who had received one prior treatment and had measurable disease were enrolled in this phase 2 study. Saracatinib was administered at 175 mg by mouth daily for 28 day cycles until dose-limiting toxicity or progression as determined by staging every 2 cycles. The primary endpoint was improvement in 4 month progression-free survival. Design of Thall, Simon, and Estey was used to monitor proportion of patients that were progression free at 4 months. The trial was opened with plan to enroll maximum of 35 patients, with futility assessment every 10 patients. RESULTS: A total of 10 patients were enrolled between January and November 2007. Further enrollment was stopped due to futility. Median progression-free survival was 7.9 weeks, with all 10 patients showing disease progression following radiographic imaging. Median overall survival was 13.5 months. All patients were deceased by time of analysis. Observed adverse events were notable for a higher than expected number of patients with grade 3 hypophosphatemia (n = 5). CONCLUSION: Saracatinib is a novel oral Src kinase inhibitor that was well tolerated but failed to meet its primary endpoint of improvement in 4 month progression-free survival as a single agent in previously treated metastatic colorectal cancer patients.

Validation of histomolecular classification utilizing histological subtype, MUC1, and CDX2 for prognostication of resected ampullary adenocarcinoma.

BACKGROUND: Outcomes for ampullary adenocarcinomas are heterogeneous, and numerous methods of categorisation exist. A histomolecular phenotype based on histology, caudal-type homeodomain transcription factor 2 (CDX2) staining and Mucin 1 (MUC1) staining has recently been tested and validated in two cohorts. We attempt to validate this classification in a large patient population. METHODS: Tissue samples from 163 patients with resected ampullary adenocarcinoma were classified based on histology and immunohistochemical expression of CDX2 and MUC1. A pancreaticobiliary histomolecular classification (PB) was defined as a sample with pancreaticobiliary histology, positive MUC1 and negative CDX2 expression. RESULTS: There were 82 deaths; median follow-up of 32.4 months; and median overall survival of 87.7 (95% CI 42.9-109.5) months. PB comprised 28.2% of the cases. Factors associated with overall survival were histological subtype (P=0.0340); T1/2 vs T3/4 (P=0.001); perineural (P<0.0001) and lymphovascular (P=0.0203) invasion; and histomolecular intestinal histomolecular phenotype (INT) vs PB phenotype (106.4 vs 21.2 months, P<0.0001). Neither MUC1 nor CDX2 was statistically significant, although MUC1 positivity defined as ⩾10% staining was significant (P=0.0023). In multivariate analysis, age (HR 1.03), PB phenotype (HR 2.26) and perineural invasion (PNI; HR 2.26) were associated with poor survival. CONCLUSIONS: The prognostic ability of histomolecular phenotype has been validated in an independent cohort of ampullary adenocarcinoma patients.

Improved Survival with Anti-VEGF Therapy in the Treatment of Unresectable Appendiceal Epithelial Neoplasms.

BACKGROUND: Currently, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy are accepted treatments for surgically resectable appendiceal epithelial neoplasms. However, for nonsurgical candidates, systemic treatment may be considered. The purpose of this analysis was to determine the benefit of biologic therapy (anti-vascular endothelial growth factor and anti-epidermal growth factor receptor) in addition to systemic chemotherapy in this select patient population. METHODS: The MD Anderson Cancer Center tumor registry was retrospectively reviewed for systemic treatment-naive appendiceal epithelial neoplasm patients registered between January 2000 to July 2007 for prior cytoreductive surgery and hyperthermic intraperitoneal chemotherapy status, histologic grade, signet ring pathology, systemic chemotherapy, biologic therapy, tumor markers (carcinoembryonic antigen, carbohydrate antigen [CA] 125, and/or CA19-9), progression-free survival (PFS), overall survival (OS), and disease control rate. Kaplan-Meier method, log-rank, and Cox proportional hazard regression models were used for statistical analysis. RESULTS: A total of 353 patients were identified; 130 patients met the inclusion criteria. Fifty-nine patients received biologic therapy. The use of the anti-vascular endothelial growth factor (VEGF) agent bevacizumab improved both OS (42 months vs. 76 months, hazard ratio 0.49 [95 % confidence interval 0.25-0.94] P = 0.03) and PFS (4 months vs. 9 months, hazard ratio 0.69 [95 % confidence interval 0.47-0.995], P = 0.047) for all histologic subtypes. Moderately differentiated tumors had an improved PFS relative to well-differentiated tumors, 9 months versus 3 months (P = 0.05). CONCLUSIONS: Bevacizumab in combination with chemotherapy appears to play a role in surgically unresectable appendiceal epithelial neoplasm patients, with an improvement in PFS and OS. Anti-VEGF agents should be strongly considered in the management of patients with higher-grade appendiceal epithelial neoplasms who are suboptimal candidates for surgical resection.

Characterizing the patterns of clonal selection in circulating tumor DNA from patients with colorectal cancer refractory to anti-EGFR treatment.

INTRODUCTION: KRAS and EGFR ectodomain-acquired mutations in patients with metastatic colorectal cancer (mCRC) have been correlated with acquired resistance to anti-EGFR monoclonal antibodies (mAbs). We investigated the frequency, co-occurrence, and distribution of acquired KRAS and EGFR mutations in patients with mCRC refractory to anti-EGFR mAbs using circulating tumor DNA (ctDNA). PATIENTS AND METHODS: Sixty-two post-treatment plasma and 20 matching pretreatment archival tissue samples from KRAS (wt) mCRC patients refractory to anti-EGFR mAbs were evaluated by high-sensitivity emulsion polymerase chain reaction for KRAS codon 12, 13, 61, and 146 and EGFR 492 mutations. RESULTS: Plasma analyses showed newly detectable EGFR and KRAS mutations in 5/62 [8%; 95% confidence interval (CI) 0.02-0.18] and 27/62 (44%; 95% CI 0.3-0.56) samples, respectively. KRAS codon 61 and 146 mutations were predominant (33% and 11%, respectively), and multiple EGFR and/or KRAS mutations were detected in 11/27 (41%) cases. The percentage of mutant allele reads was inversely correlated with time since last treatment with EGFR mAbs (P = 0.038). In the matching archival tissue, these mutations were detectable as low-allele-frequency clones in 35% of patients with plasma mutations after treatment with anti-EGFR mAbs and correlated with shorter progression-free survival (PFS) compared with the cases with no new mutations (3.0 versus 8.0 months, P = 0.0004). CONCLUSION: Newly detected KRAS and/or EGFR mutations in plasma ctDNA from patients refractory to anti-EGFR treatment appear to derive from rare, pre-existing clones in the primary tumors. These rare clones were associated with shorter PFS in patients receiving anti-EGFR treatment. Multiple simultaneous mutations in KRAS and EGFR in the ctDNA and the decline in allele frequency after discontinuation of anti-EGFR therapy in a subset of patients suggest that several resistance mechanisms can co-exist and that relative clonal burdens may change over time. Monitoring treatment-induced genetic alterations by sequencing ctDNA could identify biomarkers for treatment screening in anti-EGFR-refractory patients.

Association between KRAS mutation and lung metastasis in advanced colorectal cancer.

BACKGROUND: KRAS mutations have been associated with lung metastases at diagnosis of metastatic colorectal cancer (mCRC), but the impact of this mutation on subsequent development of lung metastasis is unknown. We investigated KRAS mutation as a predictor of lung metastasis development. METHODS: We retrospectively evaluated data from patients with mCRC whose tumour was tested for KRAS mutation from 2008 to 2010. The relationships of KRAS mutational status with time-to-lung metastasis (TTLM) and overall survival (OS) were analysed. RESULTS: Of the 494 patients identified, 202 (41%) had tumours with KRAS mutation. KRAS mutations were associated with a shorter TTLM (median 15.2 vs 22.4 months; hazard ratio=1.40; P=0.002) and a two-fold greater odds of developing lung metastases during the disease course in patients with liver-limited mCRC at diagnosis (72 vs 56%, P=0.007). Overall survival did not differ by KRAS status. CONCLUSIONS: Lung metastasis was more likely to develop during the disease course in patients whose tumour had a KRAS mutation than in those whose tumour did not have a KRAS mutation. This finding may have an impact on decision making for surgical resection of metastatic disease.

Clinicopathologic characteristics and gene expression analyses of non-KRAS 12/13, RAS-mutated metastatic colorectal cancer.

BACKGROUND: KRAS mutations in codons 12 and 13 are present in ∼40% of all colorectal cancers (CRC). Activating mutations in codons 61 and 146 of KRAS and in codons 12, 13, and 61 of NRAS also occur but are less frequent. The clinicopathologic features and gene expression profiles of this latter subpopulation of RAS-mutant colorectal tumors have not yet been clearly defined but in general are treated similarly to those with KRAS 12 or 13 mutations. PATIENTS AND METHODS: Records of patients with metastatic CRC (mCRC) treated at MD Anderson Cancer Center between December 2000 and August 2012 were reviewed for RAS (KRAS or NRAS) and BRAF mutation status, clinical characteristics, and survival outcomes. To study further with an independent cohort, data from The Cancer Genome Atlas were analyzed to define a gene expression signature for patients whose tumors feature these atypical RAS mutations and explore differences with KRAS 12/13-mutated colorectal tumors. RESULTS: Among the 484 patients reviewed, KRAS 12/13, KRAS 61/146, NRAS, and BRAF mutations were detected in 47.7%, 3.0%, 4.1%, and 7.4%, respectively, of patients who were tested for each of these aberrations. Lung metastases were more common in both the KRAS 12/13-mutated and atypical RAS-mutated cohorts relative to patients with RAS/BRAF wild-type tumors. Gene expression analyses revealed similar patterns regardless of the site of RAS mutation, and in silico functional algorithms predicted that KRAS and NRAS mutations in codons 12, 13, 61, and 146 alter the protein function and drive tumorgenesis. CONCLUSIONS: Clinicopathologic characteristics, survival outcomes, functional impact, and gene expression profiling were similar between patients with KRAS 12/13 and those with NRAS or KRAS 61/146-mutated mCRC. These clinical and bioinformatic findings support the notion that colorectal tumors driven by these RAS mutations are phenotypically similar.

Multicenter retrospective analysis of metastatic colorectal cancer (CRC) with high-level microsatellite instability (MSI-H).

BACKGROUND: The microsatellite instability-high (MSI-H) phenotype, present in 15% of early colorectal cancer (CRC), confers good prognosis. MSI-H metastatic CRC is rare and its impact on outcomes is unknown. We describe survival outcomes and the impact of chemotherapy, metastatectomy, and BRAF V600E mutation status in the largest reported cohort of MSI-H metastatic colorectal cancer (CRC). PATIENTS AND METHODS: A retrospective review of 55 MSI-H metastatic CRC patients from two institutions, Royal Melbourne Hospital (Australia) and The University of Texas MD Anderson Cancer Center (United States), was conducted. Statistical analyses utilized Kaplan-Meier method, Log-rank test, and Cox proportional hazards models. RESULTS: Median age was 67 years (20-90), 58% had poor differentiation, and 45% had stage IV disease at presentation. Median overall survival (OS) from metastatic disease was 15.4 months. Thirteen patients underwent R0/R1 metastatectomies, with median OS from metastatectomy 33.8 months. Thirty-one patients received first-line systemic chemotherapy for metastatic disease with median OS from the start of chemotherapy 11.5 months. No statistically significant difference in progression-free survival or OS was seen between fluoropyrimidine, oxaliplatin, or irinotecan based chemotherapy. BRAF V600E mutation was present in 14 of 47 patients (30%). BRAF V600E patients demonstrated significantly worse median OS; 10.1 versus 17.3 months, P = 0.03. In multivariate analyses, BRAF V600E mutants had worse OS (HR 4.04; P = 0.005), while patients undergoing metastatectomy (HR 0.11; P = <0.001) and patients who initially presented as stage IV disease had improved OS (HR 0.27; P = 0.003). CONCLUSIONS: Patients with MSI-H metastatic CRC do not appear to have improved outcomes. BRAF V600E mutation is a poor prognostic factor in MSI-H metastatic CRC.