The current state of molecular testing in the treatment of patients with solid tumors, 2019.

The world of molecular profiling has undergone revolutionary changes over the last few years as knowledge, technology, and even standard clinical practice have evolved. Broad molecular profiling is now nearly essential for all patients with metastatic solid tumors. New agents have been approved based on molecular testing instead of tumor site of origin. Molecular profiling methodologies have likewise changed such that tests that were performed on patients a few years ago are no longer complete and possibly inaccurate today. As with all rapid change, medical providers can quickly fall behind or struggle to find up-to-date sources to ensure he or she provides optimum care. In this review, the authors provide the current state of the art for molecular profiling/precision medicine, practice standards, and a view into the future ahead.

Mutational analysis of microsatellite-stable gastrointestinal cancer with high tumour mutational burden: a retrospective cohort study.

BACKGROUND: Genomic signatures contributing to high tumour mutational burden (TMB-H) independent from mismatch-repair deficiency (dMMR) or microsatellite instability-high (MSI-H) status are not well studied. We aimed to characterise molecular features of microsatellite stable (MSS) TMB-H gastrointestinal tumours. METHODS: Molecular alterations of 48 606 gastrointestinal tumours from Caris Life Sciences (CARIS) identified with next-generation sequencing were compared among MSS-TMB-H, dMMR/MSI-H, and MSS-TMB-low (L) tumours, using χ2 or Fisher's exact tests. Antitumour immune response within the tumour environment was predicted by analysing the infiltration of immune cells and immune signatures using The Cancer Genome Atlas database. The Kaplan-Meier method and the log-rank test were used to evaluate the impact of gene alterations on the efficacy of immune checkpoint inhibitors in MSS gastrointestinal cancers from the CARIS database, a Memorial Sloan Kettering Cancer Center cohort, and a Peking University Cancer Hospital cohort. FINDINGS: MSS-TMB-H was observed in 1600 (3·29%) of 48 606 tumours, dMMR/MSI-H in 2272 (4·67%), and MSS-TMB-L in 44 734 (92·03%). Gene mutations in SMAD2, MTOR, NFE2L2, RB1, KEAP1, TERT, and RASA1 might impair antitumour immune response despite TMB-H, while mutations in 16 other genes (CDC73, CTNNA1, ERBB4, EZH2, JAK2, MAP2K1, MAP2K4, PIK3R1, POLE, PPP2R1A, PPP2R2A, PTPN11, RAF1, RUNX1, STAG2, and XPO1) were related to TMB-H with enhanced antitumour immune response independent of dMMR/MSI-H, constructing a predictive model (modified TMB [mTMB]) for immune checkpoint inhibitor efficacy. Patients with any mutation in the mTMB gene signature, in comparison with patients with mTMB wildtype tumours, showed a superior survival benefit from immune checkpoint inhibitors in MSS gastrointestinal cancers in the CARIS cohort (n=95, median overall survival 18·77 months [95% CI 17·30-20·23] vs 7·03 months [5·73-8·34]; hazard ratio 0·55 [95% CI 0·31-0·99], p=0·044). In addition, copy number amplification in chromosome 11q13 (eg, CCND1, FGF genes) was more prevalent in MSS-TMB-H tumours than in the dMMR/MSI-H or MSS-TMB-L subgroups. INTERPRETATION: Not all mutations related to TMB-H can enhance antitumour immune response. More composite biomarkers should be investigated (eg, mTMB signature) to tailor treatment with immune checkpoint inhibitors. Our data also provide novel insights for the combination of immune checkpoint inhibitors and drugs targeting cyclin D1 or FGFs. FUNDING: US National Cancer Institute, Gloria Borges WunderGlo Foundation, Dhont Family Foundation, Gene Gregg Pancreas Research Fund, San Pedro Peninsula Cancer Guild, Daniel Butler Research Fund, Victoria and Philip Wilson Research Fund, Fong Research Project, Ming Hsieh Research Fund, Shanghai Sailing Program, China National Postdoctoral Program for Innovative Talents, China Postdoctoral Science Foundation, National Natural Science Foundation of China.

Peritoneal metastases from primary appendiceal and colorectal carcinomas demonstrate distinct molecular identities on comprehensive tumor analysis.

BACKGROUND AND OBJECTIVES: Published data comparing peritoneal metastases from appendiceal cancers (pAC) and colorectal cancers (pCRC) remain sparse. We compared pAC and pCRC using comprehensive tumor profiling (CTP). METHODS: CTP was performed, including next-generation sequencing and analysis of copy number variation (CNV), microsatellite instability (MSI) and tumor mutational burden (TMB). RESULTS: One hundred thirty-six pAC and 348 pCRC samples underwent CTP. The cohorts' age and gender were similar. pCRC demonstrated increased pathogenic variants (PATHs) in APC (48% vs. 3%, p < 0.01), ARID1A (12% vs. 2%, p < 0.01), BRAF (12% vs. 2%, p < 0.01), FBXW7 (7% vs. 2%, p < 0.01), KRAS (52% vs. 41%, p < 0.05), PIK3CA (15% vs. 2%, p < 0.01), and TP53 (53% vs. 23%, p < 0.01), and decreased PATHs in GNAS (8% vs. 31%, p < 0.01). There was no difference in CNV, fusion rate, or MSI. Median TMB was higher in pCRC (5.8 vs. 5.0 mutations per megabase, p = 0.0007). Rates of TMB-high tumors were similar (pAC 2.1% vs. pCRC 9.0%, p = 0.1957). pCRC had significantly more TMB-high tumors at lower thresholds. CONCLUSIONS: Despite a reduced overall TMB, pAC demonstrated mutations distinct from those seen in pCRC. These may serve as discrete biomarkers for future study.

The Essentials of Multiomics.

Within the last decade, the science of molecular testing has evolved from single gene and single protein analysis to broad molecular profiling as a standard of care, quickly transitioning from research to practice. Terms such as genomics, transcriptomics, proteomics, circulating omics, and artificial intelligence are now commonplace, and this rapid evolution has left us with a significant knowledge gap within the medical community. In this paper, we attempt to bridge that gap and prepare the physician in oncology for multiomics, a group of technologies that have gone from looming on the horizon to become a clinical reality. The era of multiomics is here, and we must prepare ourselves for this exciting new age of cancer medicine.

A Randomized Phase II Trial of mFOLFOX6 + Bevacizumab Alone or with AdCEA Vaccine + Avelumab Immunotherapy for Untreated Metastatic Colorectal Cancer.

BACKGROUND: FOLFOX plus bevacizumab is a standard of care (SOC) for first-line treatment of microsatellite-stable metastatic colorectal cancer (MSS mCRC). This study randomized patients to SOC or SOC plus avelumab (anti-PD-L1) plus CEA-targeted vaccine. METHODS: Patients with untreated MSS mCRC enrolled to a lead-in arm assessing safety of SOC + immuno-oncology agents (IO). Next, patients were randomized to SOC or SOC + IO. The primary endpoint was progression-free survival (PFS). Multiple immune parameters were analyzed. RESULTS: Six patients enrolled to safety lead-in, 10 randomized to SOC, and 10 to SOC + IO. There was no difference in median PFS comparing SOC versus SOC + IO (8.8 months (95% CI: 3.3-17.0 months) versus 10.1 months (95% CI: 3.6-16.1 months), respectively; hazard ratio 1.061 [P = .91; 95% CI: 0.380-2.966]). The objective response rate was 50% in both arms. Of patients analyzed, most (8/11) who received SOC + IO developed multifunctional CD4+/CD8+ T-cell responses to cascade antigens MUC1 and/or brachyury, compared to 1/8 who received SOC alone (P = .020). We detected post-treatment changes in immune parameters that were distinct to the SOC and SOC + IO treatment arms. Accrual closed after an unplanned analysis predicted a low likelihood of meeting the primary endpoint. CONCLUSIONS: SOC + IO generated multifunctional MUC1- and brachyury-specific CD4+/CD8+ T cells despite concurrent chemotherapy. Although a tumor-directed immune response is necessary for T-cell-mediated antitumor activity, it was not sufficient to improve PFS. Adding agents that increase the number and function of effector cells may be required for clinical benefit.

Lessons Learned in Managing Patients with Colorectal Cancer During the COVID-19 Pandemic.

OPINION STATEMENT: The COVID-19 pandemic forced us to rapidly and dramatically shift our medical priorities and decision making. With little literature or experience to rely on, the initial priority was to minimize patient exposure to the hospital and to others. It remains unclear whether cancer patients are at higher risk of infection or serious complications, or if it is our traditional therapies that place them to be at higher risk. By far, the greatest negative impact was on screening. Routine colonoscopies were considered elective, and as a result, delays in diagnosis will be felt for years to come. The most positive changes were the incorporation of tele-visits, increased use of oral therapies, alterations in treatment schedules of both chemotherapy and radiation, and an increased emphasis on neoadjuvant therapy. These too will be felt for years to come. The colorectal cancer medical community has responded collaboratively and effectively to maintain treatment and to optimize outcomes for our patients during the COVID-19 pandemic.

Transitioning from second-line to third-line therapy in metastatic colorectal cancer.

In the setting of metastatic colorectal cancer, many gains in patient outcomes have been achieved throughout the last 2 decades. A primary driver of these gains is access to more lines of therapy. In the palliative metastatic setting, all patients ultimately progress and require continued treatment sequencing. The goal is to expose patients to all lines of available therapies. It is now possible to better select patients for each therapy. Treatment selection algorithms encompass disease factors and patient characteristics, such as overall condition and age. Appropriate molecular profiling assessments should be available early in the treatment course, to drive decision-making and allow use of alternative therapies when possible. The transition to third-line therapy can be prompted by changes in imaging scans or laboratory tests, as well as changes in the patient's symptom burden. It can be problematic to delay initiation of third-line therapy when it is clinically indicated. Many oncologists will consider rechallenging patients with the same chemotherapy that did not work earlier. Although this strategy is reasonable, it should not necessarily take precedence over use of agents with proven efficacy in later lines of therapy in randomized clinical trials, such as regorafenib and trifluridine/tipiracil. Clinicians now commonly adjust the dose of regorafenib. A delay in the initiation of these third-line agents can allow the patient's performance status to decrease, thus diminishing the opportunity for a successful outcome.

Considerations in the management of younger patients with colorectal cancer.

The incidence of colorectal cancer in patients ages 18 to 49 years has increased by 51% throughout the past 3 decades. In the United States, recent guidelines lowered the initial screening age to 45 years. More than 75% of colorectal tumors in younger patients are diagnosed based on the onset of symptoms, such as rectal bleeding, abdominal pain, weight loss, or anemia. In most cases, these individuals do not have a family history of colorectal cancer. On average, the diagnosis of colorectal cancer in younger patients occurs from 6 months to several years after symptoms first arise. As a result, younger patients diagnosed with colorectal cancer tend to present with advanced disease. If a younger patient does not have any contraindications, it is appropriate to consider treatment with a triplet chemotherapy combined with a biologic. The impact of treatment can be greater for younger patients than for older individuals. Even mild or moderate toxicities can strongly impact their daily lives. Younger patients with colorectal cancer are likely to have a higher risk for long-term treatment-related sequelae, particularly because they tend to present with advanced disease and will receive therapy for a prolonged period.

Relationship between MLH1, PMS2, MSH2 and MSH6 gene-specific alterations and tumor mutational burden in 1057 microsatellite instability-high solid tumors.

Microsatellite instability-high (MSI-H) and tumor mutational burden (TMB) are predictive biomarkers for immune-checkpoint inhibitors (ICIs). Still, the relationship between the underlying cause(s) of MSI and TMB in tumors remains poorly defined. We investigated associations of TMB to mismatch repair (MMR) protein expression patterns by immunohistochemistry (IHC) and MMR mutations in a diverse sample of tumors. Hypothesized differences were identified by the protein/gene affected/mutated and the tumor histology/primary site. Overall, 1057 MSI-H tumors were identified from the 32 932 tested. MSI was examined by NGS using 7000+ target microsatellite loci. TMB was calculated using only nonsynonymous missense mutations sequenced with a 592-gene panel; a subset of MSI-H tumors also had MMR IHC performed. Analyses examined TMB by MMR protein heterodimer impacted (loss of MLH1/PMS2 vs. MSH2/MSH6 expression) and gene-specific mutations. The sample was 54.6% female; mean age was 63.5 years. Among IHC tested tumors, loss of co-expression of MLH1/PMS2 was more common (n = 544/705, 77.2%) than loss of MSH2/MSH6 (n = 81/705, 11.5%; P < .0001), and was associated with lower mean TMB (MLH1/PMS2: 25.03 mut/Mb vs MSH2/MSH6 46.83 mut/Mb; P < .0001). TMB also varied by tumor histology: colorectal cancers demonstrating MLH1/PMS2 loss had higher TMBs (33.14 mut/Mb) than endometrial cancers (20.60 mut/Mb) and other tumors (25.59 mut/Mb; P < .0001). MMR gene mutations were detected in 42.0% of tumors; among these, MSH6 mutations were most common (25.7%). MSH6 mutation patterns showed variability by tumor histology and TMB. TMB varies by underlying cause(s) of MSI and tumor histology; this heterogeneity may contribute to differences in response to ICI.

Workup and Management of Immune-Mediated Hepatobiliary Pancreatic Toxicities That Develop During Immune Checkpoint Inhibitor Treatment.

Immune checkpoint inhibitor treatment has been approved by the U.S. Food and Drug Administration for the treatment of a wide range of cancer types, including hepatocellular carcinoma. Workup and management of immune-mediated hepatitis, pancreatitis, or cholangitis that develops during immune checkpoint inhibitor treatment can be challenging. Immune-mediated hepatitis can be particularly challenging if patients have underlying viral hepatitis or autoimmune hepatitis. Patients with positive hepatitis B virus DNA should be referred to a hepatologist for antiviral therapy prior to immune checkpoint inhibitor treatment. With untreated hepatitis C virus (HCV) and elevated liver enzymes, a liver biopsy should be obtained to differentiate between HCV infection and immune-mediated hepatitis due to anti-programmed cell death protein 1 (PD-1) therapy. If autoimmune serologies are negative, then this supports a case of immune-mediated hepatitis secondary to anti-PD-1 therapy, rather than autoimmune hepatitis. In this case, an empiric steroid therapy is reasonable; however, if the patient does not respond to steroid therapy in 3-5 days, then liver biopsy should be pursued. The incidence of immune checkpoint-induced pancreatitis is low, but when it does occur, diagnosis is not straightforward. Although routine monitoring of pancreatic enzymes is not generally recommended, when pancreatitis is suspected, serum levels of amylase and lipase should be checked. Once confirmed, a steroid or other immunosuppressant (if steroids are contraindicated) should be administered along with close monitoring, and a slow tapering dosage once the pancreatitis is under control. Patients should then be monitored for recurrent pancreatitis. Finally, immune therapy-related cholangitis involves elevated bilirubin and alkaline phosphatase and, once diagnosed, is managed in the same way as immune-mediated hepatitis. KEY POINTS: Immune-mediated hepatitis, pancreatitis, and cholangitis are found in patients receiving or who have previously received immune checkpoint inhibitors. To work up immune-mediated hepatitis, viral, and autoimmune serologies, liver imaging will help to differentiate immune-mediated hepatitis from hepatitis of other etiology. Hepatology consult may be considered in patients with a history of chronic liver disease who developed hepatitis during immune checkpoint inhibitor treatment. Liver biopsy should be considered to clarify the diagnosis for case in which the hepatitis is refractory to steroid or immunosuppressant treatment. Immune-mediated pancreatitis is treated with steroid or other immunosuppressant with a slow tapering and should be monitored for recurrence.

Workup and Management of Immune-Mediated Colitis in Patients Treated with Immune Checkpoint Inhibitors.

As the use of immune checkpoint inhibitors for several different malignancies becomes more mainstream, their side-effect profile raises new challenges. In 2011, the Food and Drug Administration approved the first checkpoint inhibitor for the treatment of advanced melanoma, and since then, checkpoint inhibitors have demonstrated efficacy in many other tumor types. Given the frequent use of immune checkpoint inhibitors in a wide range of cancers today, the diagnosis and management of their immune-mediated toxicities need special attention. One of the most common is immune-mediated colitis. Workup and management of immune-mediated colitis can be challenging and is the purpose of this review. KEY POINTS: Rate of immune mediated colitis differ from different kind of immune checkpoint inhibitor treatment. To work up immune-mediated colitis, tests to rule out infectious etiologies of diarrhea, colonoscopy and abdominal image will help to differentiate immune mediated colitis from colitis from other etiology. Patients with mild colitis can be managed with supportive therapies alone, but more severe cases may require immunomodulators such as steroid. Refractory cases may require tumor necrosis factor (TNF) inhibitors, such as infliximab in addition to steroid treatment.

Molecular Analyses of Left- and Right-Sided Tumors in Adolescents and Young Adults with Colorectal Cancer.

BACKGROUND: The incidence of colorectal cancer (CRC), particularly left-sided tumors (LT), in adolescents and young adults (AYA) is rising. Epigenetic events appear to play an important role in tumorigenesis and cancer progression, especially in younger patients. We compared molecular features of LT to right-sided tumors (RT) in AYA. MATERIALS AND METHODS: A total of 246 LT and 56 RT were identified in a cohort of 612 AYA with primary CRC. Tumors were examined by next-generation sequencing (NGS), protein expression, and gene amplification. Tumor mutational burden (TMB) and microsatellite instability (MSI) were determined based on NGS data. RESULTS: RT showed higher mutation rates compared with LT in several genes including BRAF (10.3% vs. 2.8%), KRAS (64.1% vs. 45.5%), PIK3CA (27% vs. 11.2%), and RNF43 (24.2% vs. 2.9%). Notably, additional mutations in distinct genes involved in histone modification and chromatin remodeling, as well as genes associated with DNA repair and cancer-predisposing syndromes, were characteristic of RT; most frequently KMT2D (27.8% vs. 3.4%), ARID1A (53.3% vs. 21.4%), MSH6 (11.1% vs. 2.3%), MLH1 (10.5% vs. 2.3%), MSH2 (10.5% vs. 1.2%), POLE (5.9% vs. 0.6%), PTEN (10.8% vs. 2.3%), and BRCA1 (5.4% vs. 0.6%). MSI was seen in 20.8% of RT versus 4.8% of LT. RT had a higher frequency of TMB-high regardless of MSI status. CONCLUSION: Molecular profiling of AYA CRC revealed different molecular characteristics in RT versus LT. Epigenetic mechanisms and alteration in DNA repair genes warrant further investigation and may be a promising treatment target for CRC in AYA. IMPLICATIONS FOR PRACTICE: Colorectal cancer (CRC) in adolescents and young adults (AYA) comprises a distinct entity with different clinicopathologic features and prognosis compared with older patients. Molecular profiling of right- and left-sided tumors in AYA is needed to gain novel insight into CRC biology and to tailor targeted treatment in this age group. This study found that right- and left-sided CRC show distinct molecular features in AYA, overall and in subgroups based on microsatellite instability status. Alterations in DNA double-strand break repair and homologous recombination repair, as well as epigenetic mechanisms, appear to play a critical role. The present molecular profiling data may support the development of personalized treatment strategies in the AYA population.

Comprehensive tumor profiling reveals unique molecular differences between peritoneal metastases and primary colorectal adenocarcinoma.

BACKGROUND AND OBJECTIVES: Peritoneal metastases (PM) from primary colorectal cancer (pCRC) are associated with poor outcomes; however, molecular differences are not well defined. METHODS: We compared unpaired tumor profiles of patients with pCRC and PM from Caris Life Sciences. Testing included next-generation sequencing of 592 genes, microsatellite instability (MSI) and tumor mutational burden (TMB). Mutations were test-defined as pathogenic (PATH). RESULTS: Six hundred seventeen pCRC and 348 PM patients had similar gender (55% male) and age (median 59). PATHs were similar between PM and pCRC in KRAS, BRAF, SMAD2, SMAD4, and PTEN. pCRC PATHs were increased in APC (76% vs 48%, P < .01), ARID1A (29% vs 12%, P < .05), TP53 (72% vs 53%, P < .01), PIK3CA (22% vs 15%, P < .05), and FBXW7 (13% vs 7%, P < .01) compared with PM. Mucinous PM had more PATHs in GNAS (19% vs 8%, P = .032) while nonmucinous PM had more PATHs in BRAF (13% vs 8%, P = .027). Right-sided PM had decreased PATHs in APC (39% vs 68%, P < .0001), ARID1A (7% vs 38%, P < .004), and TP53 (48% vs 65%, P = .033) while there were no difference for left-sided PM. Nine percent of pCRC and 6% of PM were MSI-high (P = NS). There was no difference in TMB-high, TMB-intermediate, or TMB-low between PM and pCRC. CONCLUSIONS: PM have similar rates of KRAS mutation with increased PATHs in GNAS (mucinous) and BRAF (nonmucinous) compared to pCRC. No differences in MSI or TMB were identified between PM and pCRC tumors. These findings inform future study into the molecular profile of PM.

How to incorporate a chemo-free interval into the management of metastatic colorectal cancer.

Management of metastatic colorectal cancer reflects a continuum of care. The primary treatment goals are to prolong survival while maintaining the best quality of life. The recommended standard-of-care treatments in the first-line setting consist of combination chemotherapy regimens, given with or without biologic agents. Most patients will receive different lines of therapy for the rest of their life. In the context of lifelong therapy, incorporating chemo-free intervals is one strategy to help achieve these treatment goals. A principle of management is to ensure that all potentially active agents are available to patients. Third-line options for patients with an inadequate response to first-line and second-line therapy include regorafenib and trifluridine/tipiracil. These treatments should be initiated before the patient's performance status deteriorates. Patient characteristics should guide selection. The management plan now incorporates new lessons learned during the current global COVID-19 pandemic. One of the primary guiding principles underlying these recommendations is to avoid unnecessary clinic and hospital exposure. Telemedicine permits the remote management of patients who are receiving oral therapies. Many of these strategies will likely remain in place after the pandemic ends.

Impact of Patient Age on Molecular Alterations of Left-Sided Colorectal Tumors.

BACKGROUND: The incidence of colorectal cancer (CRC) in younger patients is rising, mostly due to tumors in the descending colon and rectum. Therefore, we aimed to explore the molecular differences of left-sided CRC between younger (≤45 years) and older patients (≥65). SUBJECTS, MATERIALS, AND METHODS: In total, 1,126 CRC tumor samples from the splenic flexure to (and including) the rectum were examined by next-generation sequencing (NGS), immunohistochemistry, and in situ hybridization. Microsatellite instability (MSI) and tumor mutational burden (TMB) were assessed by NGS. RESULTS: Younger patients (n = 350), when compared with older patients (n = 776), showed higher mutation rates in genes associated with cancer-predisposing syndromes (e.g., Lynch syndrome), such as MSH6 (4.8% vs. 1.2%, p = .005), MSH2 (2.7% vs. 0.0%, p = .004), POLE (1.6% vs. 0.0%, p = .008), NF1 (5.9% vs. 0.5%, p < .001), SMAD4 (14.3% vs. 8.3%, p = .024), and BRCA2 (3.7% vs. 0.5%, p = .002). Genes involved in histone modification were also significantly more mutated: KDM5C (1.9% vs. 0%, p = .036), KMT2A (1.1% vs. 0%, p = .033), KMT2C (1.6% vs. 0%, p = .031), KMT2D (3.8% vs. 0.7%, p = .005), and SETD2 (3.2% vs. 0.9%, p = .039). Finally, TMB-high (9.7% vs. 2.8%, p < .001) and MSI-high (MSI-H; 8.1% vs. 1.9%, p = .009) were more frequent in younger patients. CONCLUSION: Our findings highlight the importance of genetic counseling and screening in younger CRC patients. MSI-H and TMB-high tumors could benefit from immune-checkpoint inhibitors, now approved for the treatment of MSI-H/deficient mismatch repair metastatic CRC patients. Finally, histone modifiers could serve as a new promising therapeutic target. With confirmatory studies, these results may influence our approach to younger adults with CRC. IMPLICATIONS FOR PRACTICE: The increasing rate of colorectal cancers (CRC), primarily distal tumors, among young adults poses a global health issue. This study investigates the molecular differences between younger (≤45 years old) and older (≥65) adults with left-sided CRCs. Younger patients more frequently harbor mutations in genes associated with cancer-predisposing syndromes. Higher rates of microsatellite instability-high and tumor mutational burden-high tumors occur in younger patients, who could benefit from immune-checkpoint inhibitors. Finally, histone modifiers are more frequently mutated in younger patients and could serve as a new promising therapeutic target. This study provides new insights into mutations that may guide development of novel tailored therapy in younger CRC patients.

Colon Cancer in Young Adults: Trends and Their Implications.

PURPOSE OF REVIEW: The recent rise of young individuals under age 50 with colorectal cancer (CRC) is a startling trend in need of greater focus and research. The etiology of young-onset CRC is unexplained as efforts to blame obesity or diabetes as causative factors are simplistic and inadequate. RECENT FINDINGS: We describe the epidemiologic shifts of CRC incidence and mortality across age groups as well as the differences in clinicopathologic, molecular, treatment, and survival characteristics between young and older patients. Novel studies of the microbiome may elucidate bacterial causes of CRC carcinogenesis in younger individuals. Moving up the colonoscopy screening to age 45 in normal-risk individuals should prove beneficial in detecting more patients with early-onset CRC. We favor the development of risk-adaptive screening decision algorithms and flexible sigmoidoscopy screening at age 40 given the predilection for left-sided primaries in this age group. More awareness and attention to young-onset CRC will be critical to improve outcomes in this patient population.

Biomarkers for immune therapy in gastrointestinal cancers.

Immunotherapy with checkpoint blockade of pro-grammed death 1 (PD-1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) has substantially increased the number of anticancer agents in our arsenal. However, these therapies are not effective in all cancer types, benefitting only a subset of patients with susceptible, immunogenic cancers. This problem is especially significant in gastrointestinal malignancies, which infrequently respond to immunotherapy. Although we clearly need more accurate biomarkers to predict response to immune checkpoint inhibition in gastrointestinal cancers, the established markers of mismatch repair deficiency, microsatellite instability, programmed death ligand 1 (PD-L1) expression, and tumor mutational burden are good starting points to identify patients who may benefit. Tumor-infiltrating lymphocytes, Epstein-Barr virus, and the stool microbiome are candidates for future immuno-oncology biomarkers in gastrointestinal malignancies. The availability of better biomarkers will improve patient selection for immunotherapy; it will also improve the design of clinical trials of agents intended for this population of patients, who require more effective treatment options.

Sequencing beyond the second-line setting in metastatic colorectal cancer.

The standard treatment for patients with metastatic colorectal cancer (mCRC) in the first- and second-line setting is generally chemotherapy, which can be augmented with vascular endothelial growth factor-targeted therapies and, for patients with KRAS wild-type status, epidermal growth factor receptor-targeted therapies. However, nearly all patients ultimately develop disease progression and require later lines of therapy. Traditionally, physicians recycled chemotherapy in the later lines, with many patients showing diminished or no response. However, the past several years have seen the introduction of 2 agents for patients with refractory mCRC entering the third-line setting. The multitargeted tyrosine kinase inhibitor regorafenib and the cytotoxic combination of trifluridine/tipiracil have demonstrated significant improvements in overall survival in patients with refractory mCRC. Although these agents do not seem to induce complete responses, they can lead to durable stable disease. Regorafenib and trifluridine/tipiracil differ in their safety profiles. Physicians and patients must be properly educated on how to recognize and mitigate adverse events. For regorafenib, a dose-escalating strategy improves tolerability without impacting efficacy. When sequencing these agents, physicians should consider patient characteristics, including comorbidities, prior adverse reactions to treatments, and overall performance status. Ongoing studies are further defining the role of regorafenib and trifluridine/tipiracil in the treatment of mCRC.

A phase 2 study of the PARP inhibitor veliparib plus temozolomide in patients with heavily pretreated metastatic colorectal cancer.

BACKGROUND: Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors such as veliparib are potent sensitizing agents and have been safely combined with DNA-damaging agents such as temozolomide. The sensitizing effects of PARP inhibitors are magnified when cells harbor DNA repair defects. METHODS: A single-arm, open-label, phase 2 study was performed to investigate the disease control rate (DCR) after 2 cycles of veliparib plus temozolomide in patients with metastatic colorectal cancer (mCRC) refractory to all standard therapies. Fifty patients received temozolomide (150 mg/m2 /d) on days 1 to 5 and veliparib (40 mg twice daily) on days 1 to 7 of each 28-day cycle. Another 5 patients with mismatch repair-deficient (dMMR) tumors were also enrolled. Twenty additional patients were then treated with temozolomide at 200 mg/m2 /d. Archived tumor specimens were used for immunohistochemistry to assess mismatch repair, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and O(6)-methylguanine-DNA methyltransferase (MGMT) protein expression levels. RESULTS: The combination was well tolerated, although some patients required dose reductions for myelosuppression. The primary endpoint was successfully met with a DCR of 24% and 2 confirmed partial responses. The median progression-free survival was 1.8 months, and the median overall survival was 6.6 months. PTEN protein expression and MGMT protein expression were not predictors of DCR. There was also a suggestion of worse outcomes for patients with dMMR tumors. CONCLUSIONS: In this heavily pretreated mCRC population, a combination of veliparib and temozolomide was well tolerated with temozolomide doses up to 200 mg/m2 /d, and it was clinically active. PARP inhibitor-based therapy merits further exploration in patients with mCRC. Cancer 2018;124:2337-46. © 2018 American Cancer Society.

Immuno-Oncology Biomarkers for Gastric and Gastroesophageal Junction Adenocarcinoma: Why PD-L1 Testing May Not Be Enough.

PURPOSE: The treatment of patients with advanced gastric and gastroesophageal junction (G/GEJ) adenocarcinomas has been transformed by the U.S. Food and Drug Administration approval of pembrolizumab. Tumor and adjacent tissue must stain positively for the programmed cell death ligand 1 (PD-L1) protein by companion diagnostic testing. However, some patients with PD-L1-negative tumors also benefit from pembrolizumab. High microsatellite instability (MSI) and tumor mutational load (TML) are positive predictive biomarkers for immune checkpoint inhibition (ICI) in other tumors. We sought to identify more patients who could benefit from ICI using alternative PD-L1 thresholds, MSI, and TML. METHODS: Tumor specimens underwent next-generation sequencing (NGS) and PD-L1 testing using immunohistochemistry. NGS was used to determine TML and MSI. RESULTS: We profiled 581 G/GEJ adenocarcinoma specimens. PD-L1 staining was scored for intensity (0, none; 1+, weak; 2+, moderate; 3+, strong). Using 2+ staining at a 5% threshold, 9.3% of tumors were PD-L1 positive, and using 1+ staining at 1%, 16.2% were PD-L1 positive. 6.9% of tumors had high MSI. High TML (≥17 mutations per megabase) was seen in 6.9%, and medium TML (≥7) was seen in 56.5% of tumors. Thirty (5.2%) PD-L1-negative tumors at the 1+, 1% threshold had high TML or high MSI. Primary tumors had higher rates of high TML (8.8% vs. 3.9%; p = .0377) and high MSI (8.5% vs. 3.9%; p = .0471) than metastases. CONCLUSION: PD-L1 testing alone fails to detect patients who may benefit from ICI. Lower PD-L1 thresholds and TML testing should be considered in future clinical trials. IMPLICATIONS FOR PRACTICE: Pembrolizumab is approved by the U.S. Food and Drug Administration for patients with refractory gastric and gastroesophageal cancers if the tumor and adjacent tissue stain positively for the programmed cell death ligand 1 (PD-L1) protein by companion diagnostic testing. Tumor mutational load, microsatellite instability (MSI), and alternative PD-L1 testing thresholds may serve as predictive biomarkers for response to immune checkpoint inhibition, and standard PD-L1 testing will not identify all patients who may benefit from this therapy.