Explore the vast range of titles available.

Following initial successes in melanoma treatment, immunotherapy has rapidly become established as a major treatment modality for multiple types of solid cancers, including a subset of colorectal cancers (CRCs). Two programmed cell death 1 (PD1)-blocking antibodies, pembrolizumab and nivolumab, have shown efficacy in patients with metastatic CRC that is mismatch-repair-deficient and microsatellite instability-high (dMMR–MSI-H), and have been granted accelerated FDA approval. In contrast to most other treatments for metastatic cancer, immunotherapy achieves long-term durable remission in a subset of patients, highlighting the tremendous promise of immunotherapy in treating dMMR–MSI-H metastatic CRC. Here, we review the clinical development of immune checkpoint inhibition in CRC leading to regulatory approvals for the treatment of dMMR–MSI-H CRC. We focus on new advances in expanding the efficacy of immunotherapy to early-stage CRC and CRC that is mismatch-repair-proficient and has low microsatellite instability (pMMR–MSI-L) and discuss emerging approaches for targeting the immune microenvironment, which might complement immune checkpoint inhibition.Ganesh et al. describe the rationale for using immunotherapy in select patients with colorectal cancer, discuss clinical findings supporting its use and highlight current strategies and future directions for expanding the scope of immunotherapy in this disease.

Colorectal cancer is genetically heterogeneous. Tumors in some patients have defects in mismatch DNA repair. These tumors have a high level of mutations that can lead to immune recognition. In a group of patients with microsatellite-unstable tumors, pembrolizumab led to longer progression-free survival and was less toxic than standard chemotherapy.

More than 2% of adults harbor a pancreatic cyst, a subset of which progresses to invasive lesions with lethal consequences. To assess the genomic landscapes of neoplastic cysts of the pancreas, we determined the exomic sequences of DNA from the neoplastic epithelium of eight surgically resected cysts of each of the major neoplastic cyst types: serous cystadenomas (SCAs), intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCNs), and solid pseudopapillary neoplasms (SPNs). SPNs are low-grade malignancies, and IPMNs and MCNs, but not SCAs, have the capacity to progress to cancer. We found that SCAs, IPMNs, MCNs, and SPNs contained 10 ± 4.6, 27 ± 12, 16 ± 7.6, and 2.9 ± 2.1 somatic mutations per tumor, respectively. Among the mutations identified, E3 ubiquitin ligase components were of particular note. Four of the eight SCAs contained mutations of the von Hippel–Lindau gene (VHL), a key component of the VHL ubiquitin ligase complex that has previously been associated with renal cell carcinomas, SCAs, and other neoplasms. Six of the eight IPMNs and three of the eight MCNs harbored mutations of RNF43, a gene coding for a protein with intrinsic E3 ubiquitin ligase activity that has not previously been found to be genetically altered in any human cancer. The preponderance of inactivating mutations in RNF43 unequivocally establish it as a suppressor of both IPMNs and MCNs. SPNs contained remarkably few genetic alterations but always contained mutations of CTNNB1, previously demonstrated to inhibit degradation of the encoded protein (β-catenin) by E3 ubiquitin ligases. These results highlight the essential role of ubiquitin ligases in these neoplasms and have important implications for the diagnosis and treatment of patients with cystic tumors.

The effect of somatic genetic changes in colorectal cancer on sensitivity to anti-EGFR antibody therapy is analysed. Genomics of a cancer during targeted therapy Victor Velculescu and colleagues examine the effect of somatic genetic changes in colorectal cancer on sensitivity to a common targeted therapy. Exome sequencing, copy number and targeted analyses of tumour response to anti-EGFR antibody blockade identified mutations in ERBB2 , EGFR , FGFR1 , PDGFRA , and MAP2K1 as potential mechanisms of primary resistance to this therapy. Therapeutic resistance to EGFR blockade could be overcome in tumour graft models through combinatorial therapies targeting actionable genes. In addition to highlighting new mechanisms of responsiveness to anti-EGFR therapies, this work provides new avenues for intervention in the management of colorectal cancer. Colorectal cancer is the third most common cancer worldwide, with 1.2 million patients diagnosed annually. In late-stage colorectal cancer, the most commonly used targeted therapies are the monoclonal antibodies cetuximab and panitumumab, which prevent epidermal growth factor receptor (EGFR) activation 1 . Recent studies have identified alterations in KRAS 2 , 3 , 4 and other genes 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 as likely mechanisms of primary and secondary resistance to anti-EGFR antibody therapy. Despite these efforts, additional mechanisms of resistance to EGFR blockade are thought to be present in colorectal cancer and little is known about determinants of sensitivity to this therapy. To examine the effect of somatic genetic changes in colorectal cancer on response to anti-EGFR antibody therapy, here we perform complete exome sequence and copy number analyses of 129 patient-derived tumour grafts and targeted genomic analyses of 55 patient tumours, all of which were KRAS wild-type. We analysed the response of tumours to anti-EGFR antibody blockade in tumour graft models and in clinical settings and functionally linked therapeutic responses to mutational data. In addition to previously identified genes, we detected mutations in ERBB2 , EGFR , FGFR1 , PDGFRA , and MAP2K1 as potential mechanisms of primary resistance to this therapy. Novel alterations in the ectodomain of EGFR were identified in patients with acquired resistance to EGFR blockade. Amplifications and sequence changes in the tyrosine kinase receptor adaptor gene IRS2 were identified in tumours with increased sensitivity to anti-EGFR therapy. Therapeutic resistance to EGFR blockade could be overcome in tumour graft models through combinatorial therapies targeting actionable genes. These analyses provide a systematic approach to evaluating response to targeted therapies in human cancer, highlight new mechanisms of responsiveness to anti-EGFR therapies, and delineate new avenues for intervention in managing colorectal cancer.

The measurement of circulating nucleic acids has transformed the management of chronic viral infections such as HIV. The development of analogous markers for individuals with cancer could similarly enhance the management of their disease. DNA containing somatic mutations is highly tumor specific and thus, in theory, can provide optimum markers. However, the number of circulating mutant gene fragments is small compared to the number of normal circulating DNA fragments, making it difficult to detect and quantify them with the sensitivity required for meaningful clinical use. In this study, we applied a highly sensitive approach to quantify circulating tumor DNA (ctDNA) in 162 plasma samples from 18 subjects undergoing multimodality therapy for colorectal cancer. We found that ctDNA measurements could be used to reliably monitor tumor dynamics in subjects with cancer who were undergoing surgery or chemotherapy. We suggest that this personalized genetic approach could be generally applied to individuals with other types of cancer ( pages 914–915 ).

The FDA has approved immune checkpoint inhibitors for solid tumors of any histologic origin with more than 10 mutations per megabase of DNA. This study showed that in tumors with high mutational burden treated with an immune checkpoint inhibitor, improved overall survival was associated mainly with mutations in the POLE gene and with defective DNA mismatch repair, not overall mutational burden.

Over the past decade, comprehensive sequencing efforts have revealed the genomic landscapes of common forms of human cancer. For most cancer types, this landscape consists of a small number of \"mountains\" (genes altered in a high percentage of tumors) and a much larger number of \"hills\" (genes altered infrequently). To date, these studies have revealed ~140 genes that, when altered by intragenic mutations, can promote or \"drive\" tumorigenesis. A typical tumor contains two to eight of these \"driver gene\" mutations; the remaining mutations are passengers that confer no selective growth advantage. Driver genes can be classified into 12 signaling pathways that regulate three core cellular processes: cell fate, cell survival, and genome maintenance. A better understanding of these pathways is one of the most pressing needs in basic cancer research. Even now, however, our knowledge of cancer genomes is sufficient to guide the development of more effective approaches for reducing cancer morbidity and mortality.

Pembrolizumab has shown improved progression-free survival versus chemotherapy in patients with newly diagnosed microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. However, the treatment's effect on overall survival in this cohort of patients was unknown. Here, we present the final overall survival analysis of the KEYNOTE-177 study. This randomised, open-label, phase 3 study was done in 193 academic medical centres and hospitals in 23 countries. We recruited patients aged at least 18 years, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. Patients were randomly assigned (1:1) in blocks of four using an interactive voice response system or integrated web response system to intravenous pembrolizumab 200 mg every 3 weeks or to the investigator's choice of intravenous mFOLFOX6 (oxaliplatin 85 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1–2) or intravenous FOLFIRI (irinotecan 180 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1–2), every 2 weeks with or without intravenous bevacizumab 5 mg/kg every 2 weeks or intravenous weekly cetuximab (first dose 400 mg/m2, then 250 mg/m2 for every subsequent dose). Patients receiving chemotherapy could cross over to pembrolizumab for up to 35 treatment cycles after progression. The co-primary endpoints were overall survival and progression-free survival in the intention-to-treat population. KEYNOTE-177 is registered at ClinicalTrials.gov, NCT02563002, and is no longer enrolling patients. Between Feb 11, 2016, and Feb 19, 2018, 852 patients were screened, of whom 307 (36%) were randomly assigned to pembrolizumab (n=153) or chemotherapy (n=154). 93 (60%) patients crossed over from chemotherapy to anti-PD-1 or anti-PD-L1 therapy (56 patients to on-study pembrolizumab and 37 patients to off-study therapy). At final analysis (median follow-up of 44·5 months [IQR 39·7–49·8]), median overall survival was not reached (NR; 95% CI 49·2–NR) with pembrolizumab vs 36·7 months (27·6–NR) with chemotherapy (hazard ratio [HR] 0·74; 95% CI 0·53–1·03; p=0·036). Superiority of pembrolizumab versus chemotherapy for overall survival was not demonstrated because the prespecified α of 0·025 needed for statistical significance was not achieved. At this updated analysis, median progression-free survival was 16·5 months (95% CI 5·4–38·1) with pembrolizumab versus 8·2 months (6·1–10·2) with chemotherapy (HR 0·59, 95% CI 0·45–0·79). Treatment-related adverse events of grade 3 or worse occurred in 33 (22%) of 153 patients in the pembrolizumab group versus 95 (66%) of 143 patients in the chemotherapy group. Common adverse events of grade 3 or worse that were attributed to pembrolizumab were increased alanine aminotransferase, colitis, diarrhoea, and fatigue in three (2%) patients each, and those attributed to chemotherapy were decreased neutrophil count (in 24 [17%] patients), neutropenia (22 [15%]), diarrhoea (14 [10%]), and fatigue (13 [9%]). Serious adverse events attributed to study treatment occurred in 25 (16%) patients in the pembrolizumab group and in 41 (29%) patients in the chemotherapy group. No deaths attributed to pembrolizumab occurred; one death due to intestinal perforation was attributed to chemotherapy. In this updated analysis, although pembrolizumab continued to show durable antitumour activity and fewer treatment-related adverse events compared with chemotherapy, there was no significant difference in overall survival between the two treatment groups. These findings support pembrolizumab as an efficacious first-line therapy in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. MSD.

In the KEYNOTE-177 study, pembrolizumab monotherapy provided statistically significant and clinically meaningful improvements in progression-free survival versus chemotherapy as first-line treatment in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. To further support the efficacy and safety findings of the KEYNOTE-177 study, results of the health-related quality of life (HRQOL) analyses are reported here. KEYNOTE-177 is an open-label, randomised, phase 3 trial being done at 192 cancer centres in 23 countries, in patients aged 18 years and older with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had not received previous systemic therapy for metastatic disease. Eligible patients were randomly assigned (1:1) centrally by use of interactive voice response or integrated web response technology to receive pembrolizumab 200 mg intravenously every 3 weeks or investigator's choice chemotherapy (mFOLFOX6 [leucovorin, fluorouracil, and oxaliplatin] or FOLFIRI [leucovorin, fluorouracil, and irinotecan] intravenously every 2 weeks with or without intravenous bevacizumab or cetuximab). Patients and investigators were not masked to treatment assignment. The primary endpoints were progression-free survival (previously reported) and overall survival (data to be reported at the time of the final analysis). HRQOL outcomes were evaluated as prespecified exploratory endpoints. The analysis population comprised all randomly assigned patients who received at least one dose of study treatment and completed at least one HRQOL assessment. HRQOL outcomes were mean change from baseline to prespecified week 18 in European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and EORTC Quality of Life Questionnaire-Colorectal 29 (EORTC QLQ-CR29) scale and item scores, and in the EuroQoL 5 Dimensions 3 Levels (EQ-5D-3L) visual analogue scale and health utility scores; the proportion of patients with improved, stable, or deteriorated scores from baseline to prespecified week 18 in EORTC QLQ-C30 scales and items; and time to deterioration in EORTC QLQ-C30 global health status/quality of life (GHS/QOL), physical functioning, social functioning, and fatigue scores and EORTC QLQ-CR29 urinary incontinence scores. The threshold for a small and clinically meaningful mean difference in EORTC QLQ-C30 score was 5–8 points. This study is registered with ClinicalTrials.gov, NCT02563002 and is ongoing; recruitment is closed. Between Feb 11, 2016, and Feb 19, 2018, 307 patients were enrolled and randomly assigned to receive pembrolizumab (n=153) or chemotherapy (n=154). The HRQOL analysis population comprised 294 patients (152 receiving pembrolizumab and 142 receiving chemotherapy). As of Feb 19, 2020, median time from randomisation to data cutoff was 32·4 months (IQR 27·7–37·8). Least squares mean (LSM) change from baseline to prespecified week 18 showed a clinically meaningful improvement in EORTC QLQ-C30 GHS/QOL scores with pembrolizumab versus chemotherapy (between-group LSM difference 8·96 [95% CI 4·24–13·69]; two-sided nominal p=0·0002). Median time to deterioration was longer with pembrolizumab versus chemotherapy for GHS/QOL (hazard ratio 0·61 [95% CI 0·38–0·98]; one-sided nominal p=0·019), physical functioning (0·50 [95% CI 0·32–0·81]; one-sided nominal p=0·0016), social functioning (0·53 [95% CI 0·32–0·87]; one-sided nominal p=0·0050), and fatigue scores (0·48 [95% CI 0·33–0·69]; one-sided nominal p<0·0001). Pembrolizumab monotherapy led to clinically meaningful improvements in HRQOL compared with chemotherapy in patients with previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. These data, along with the previously reported clinical benefits, support pembrolizumab as a first-line treatment option for this population. Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ, USA.

This work on colorectal cancer shows that secondary mutations in KRAS that confer resistance to panitumumab, an anti-EGFR monoclonal antibody, are already present when antibody treatment begins; the apparent inevitability of resistance suggests that combinations of drugs targeting at least two different oncogenic pathway will be needed for treatment. Acquired resistance in anti-EGFR therapy Antibodies targeting epidermal growth factor receptor (EGFR) have become an established treatment for colorectal cancer, but they are contraindicated in patients carrying mutations in the KRAS oncogene. Drug resistance can also arise in initially responsive patients, and two papers in this issue of Nature present unequivocal evidence that mutations in KRAS underlie acquired resistance to anti-EGFR antibodies in many patients and that KRAS mutations can be detected in the serum of patients before the clinical emergence of resistance and relapse. Misale et al . show in cell-line models that KRAS mutations can confer resistance to cetuximab. And in colorectal cancer patients treated with cetuximab or panitumumab, resistance is associated with KRAS mutations selected from pre-existing subclones or acquired during treatment. Diaz et al . also find KRAS mutations accumulating in patients becoming resistant to panitumumab. Their mathematical models suggest that KRAS mutations pre-existed in tumour cells before therapy, which may explain why clinical recurrence is usually seen after about six months of treatment, by which time the resistant subpopulations of tumour cells with KRAS mutations has expanded. The apparent inevitability of resistance suggests that combinations of drugs targeting more than one oncogenic pathway will be needed if resistance is to be avoided. Colorectal tumours that are wild type for KRAS are often sensitive to EGFR blockade, but almost always develop resistance within several months of initiating therapy 1 , 2 . The mechanisms underlying this acquired resistance to anti-EGFR antibodies are largely unknown. This situation is in marked contrast to that of small-molecule targeted agents, such as inhibitors of ABL, EGFR, BRAF and MEK, in which mutations in the genes encoding the protein targets render the tumours resistant to the effects of the drugs 3 , 4 , 5 , 6 . The simplest hypothesis to account for the development of resistance to EGFR blockade is that rare cells with KRAS mutations pre-exist at low levels in tumours with ostensibly wild-type KRAS genes. Although this hypothesis would seem readily testable, there is no evidence in pre-clinical models to support it, nor is there data from patients. To test this hypothesis, we determined whether mutant KRAS DNA could be detected in the circulation of 28 patients receiving monotherapy with panitumumab, a therapeutic anti-EGFR antibody. We found that 9 out of 24 (38%) patients whose tumours were initially KRAS wild type developed detectable mutations in KRAS in their sera, three of which developed multiple different KRAS mutations. The appearance of these mutations was very consistent, generally occurring between 5 and 6 months following treatment. Mathematical modelling indicated that the mutations were present in expanded subclones before the initiation of panitumumab treatment. These results suggest that the emergence of KRAS mutations is a mediator of acquired resistance to EGFR blockade and that these mutations can be detected in a non-invasive manner. They explain why solid tumours develop resistance to targeted therapies in a highly reproducible fashion.