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Molecular testing to select the appropriate targeted and standard of care therapies is essential for managing patients with colorectal cancer (CRC). The Japanese Society of Medical Oncology previously published clinical guidelines for molecular testing in CRC. In the third edition published in 2018, RAS and BRAF V600E mutations should be tested prior to first‐line chemotherapy to assess the benefit of anti–epidermal growth factor receptor (EGFR) antibody therapy in patients with unresectable CRC. Microsatellite instability (MSI) testing was recommended in patients with curatively resected stage II CRC because deficient mismatch repair is associated with low risk of recurrence. MSI testing was also recommended in patients with CRC suspected to be Lynch syndrome. The main aim of this fourth edition is to reflect recent advances in comprehensive genomic profiling (CGP) tests and liquid biopsy. Here, CGP tests performed on tumor tissues are strongly recommended to assess the benefit of molecular targeted drugs in patients with CRC. Circulating tumor DNA (ctDNA)‐based CGP tests are also proposed. ctDNA testing is recommended to determine the optimal treatment based on the risk of recurrence for curatively resected CRC and evaluate the suitability and monitor the therapeutic effects of anti–EGFR antibodies in patients with unresectable CRC. While both MSI testing and immunohistochemistry are strongly recommended to determine the indication of immune checkpoint inhibitors in patients with unresectable CRC, next‐generation sequencing‐based tests are weakly recommended because these tests have not been validated in clinical trials. Update to the molecular testing guideline for colorectal cancer defined by Japanese Society of Medical Oncology. The appropriate timing of each test and degree of recommendation are summarized.

Purpose A phase III trial comparing S-1 and docetaxel with S-1 alone as postoperative chemotherapy for pathologically Stage III gastric cancer was conducted and clarified the superiority of the doublet in terms of 3-year relapse-free survival as the primary endpoint (67.7% versus 57.4%, hazard ratio [HR] 0.715, 95% confidence interval [CI] 0.587–0.871; p  = 0.0008). This final report analyzed 5-year survival outcomes along with the incidence and pattern of late recurrences. Patients and methods Patients with histologically confirmed Stage III gastric cancer who underwent gastrectomy with D2 lymphadenectomy were randomly assigned to receive adjuvant chemotherapy with either S-1 plus docetaxel or S-1 alone. The same 912 patients who were evaluated for 3-year survival outcomes in the previous report were analyzed. Results Five-year overall survival rate of the S-1 plus docetaxel group (67.91%) was significantly superior to that in the S-1 group (60.27%; HR 0.752, 95% CI 0.613–0.922; p  = 0.0059). The incidence of late recurrence at > 3 years after randomization was similar in both groups (7.3% versus 7.2%). Peritoneal dissemination was the most common pattern of late recurrence. Addition of docetaxel significantly suppressed relapse through the lymphatic (6.8% [95% CI 4.52–9.17] versus 15% [95% CI 11.76–18.30]; p  < 0.0001) and hematogenous (10.2% [95% CI 7.37–12.94] versus 15.7% [95% CI 12.36–19.01]; p  < 0.0137) pathways throughout the 5 years of follow-up. Conclusion The survival benefit of postoperative chemotherapy with S-1 and docetaxel in terms of 5-year overall survival rate was confirmed for patients with pathologically Stage III gastric cancer, although late recurrences were not prevented.

The clinical significance of FOLFOXIRI (5-FU, leucovorin, oxaliplatin, and irinotecan) plus anti-EGFR monoclonal antibody using cetuximab for metastatic colorectal cancer (mCRC) remains controversial. We report results from a randomized phase 2 DEEPER trial (UMIN000018217, jRCTs061180022) to test the superiority of modified (m)-FOLFOXIRI plus weekly cetuximab over bevacizumab in patients with RAS wild-type (wt) mCRC. Primary endpoint was depth of response (DpR). Secondary endpoints included objective response rate (ORR), early tumor shrinkage (ETS) at week 8, progression-free survival (PFS), overall survival (OS), time to tumor growth (TTG), time to treatment failure (TTF), association between tumor shrinkage and prognosis, association between TTG and prognosis, R0 resection rate, and safety. In 359 enrolled patients with RAS wt mCRC, median DpR was significantly better in cetuximab (57.3% vs 46.0%, p  = 0.0029); however, ORR, ETS, R0 resection rate, TTG, TTF, PFS and OS were similar between 2 treatments. There was a weak association between DpR and survival time in both treatments. The correlation between TTG and OS was slightly stronger in cetuximab. The post-hoc exploratory analysis showed that cetuximab produced greater PFS (15.3 vs 11.7 months; HR 0.68) and OS (53.6 vs 40.2 months; HR 0.54) in patients with left-sided and RAS / BRAF wt tumors. m-FOLFOXIRI plus cetuximab has clinical benefit for tumor shrinkage in RAS wt mCRC. The survival benefit for RAS / BRAF wt and left-sided mCRC needs further investigation. Anti-EGFR therapy plus doublet chemotherapy is standard of care for patients with RAS wild-type metastatic colorectal cancer (mCRC) but the role of triplet chemotherapy is unclear. Here, the authors report a randomised phase 2 trial testing the superiority of adding cetuximab (anti-EGFR) over bevacizumab (anti-VEGF) to modified FOLFOXIRI (5-FU, leucovorin, oxaliplatin and irinotecan) in patients with RAS wild-type mCRC.

“Neo RAS WT” refers to the loss of RAS mutations (MTs) following first-line treatment in metastatic colorectal cancer (mCRC). We evaluate the incidence and clinicopathological characteristics of Neo RAS WT mCRC using next-generation sequencing of plasma circulating tumor DNA. Patients with mCRC enrolled in the GOZILA study initially diagnosed with tissue RAS MT mCRC and received subsequent systemic therapy are eligible. Neo RAS WT is defined as the absence of detectable RAS MT in plasma and assessed in all eligible patients (Group A) and in a subgroup with at least one somatic alteration detected in plasma (Group B). Overall, 478 patients are included. Neo RAS WT prevalence is 19.0% (91/478) in Group A and 9.8% (42/429) in Group B. Absence of liver or lymph node metastasis and tissue RAS MTs other than KRAS exon 2 MTs are significantly associated with Neo RAS WT emergence. Overall, 1/6 and 2/6 patients with Neo RAS WT treated with anti-EGFR monoclonal antibodies (mAbs) show partial response and stable disease for ≥6 months, respectively. Neo RAS WT mCRC is observed at a meaningful prevalence, and anti-EGFR mAb-based therapy may be effective. RAS mutations have been shown to be lost after first line treatment for metastatic colorectal cancer. Here, the authors leverage the GOZILA study to identify these patients and identify their association with other risk factor.

Background Previous clinical trials have demonstrated the potential efficacy of rechallenge with anti- epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs) for patients with RAS / BRAF V600E wild-type metastatic colorectal cancer (mCRC). Moreover, post hoc biomarker analyses of clinical trials has suggested that RAS status in circulating tumor DNA (ctDNA) has a high probability to select patients who could benefit from anti-EGFR mAb rechallenge. Methods This trial is composed of 2 phases: a monitoring phase (REMARRY) and a trial phase (PURSUIT). A monitoring phase, the REMARRY study, aims to evaluate the dynamics of plasma RAS status during the subsequent treatments after refractory to anti-EGFR therapy in patients with mCRC with RAS / BRAF V600E wild-type tumors who have progressed after a response to previous anti-EGFR therapy, using a highly sensitive digital polymerase chain reaction OncoBEAM RAS CRC kit in a central laboratory (Sysmex, Japan). A trial phase, the PURSUIT trial, is a multicenter, single-arm phase II trial to assess the efficacy and safety of rechallenge therapy with panitumumab plus irinotecan in patients without RAS mutations in ctDNA (plasma RAS negative) in the REMARRY study. Key eligibility criteria of the PURSUIT trial include RAS / BRAF V600E wild-type mCRC in tumor tissue refractory or intolerant to fluoropyrimidine, oxaliplatin, and irinotecan; progression after complete or partial response to previous anti-EGFR therapy; plasma RAS negative (defined as plasma mutant allele frequencies [MAF] of all RAS  ≤ 0.1%) within 28 days prior to enrollment; 4 months or more between the last administration of previous anti-EGFR mAb and the start of protocol treatment; and Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) ≤ 1. The primary endpoint is the confirmed objective response rate (ORR). The target sample size of the PURSUIT trial is 50 patients. Biomarker analyses will be performed in parallel using the OncoBEAM RAS CRC kit and a next-generation sequencing-based ctDNA analysis (Guardant360). Discussion Our trial aims to confirm the clinical benefit of anti-EGFR mAb rechallenge therapy in patients with plasma RAS negative. Moreover, through biomarker analyses, our trial will shed light on which patients would benefit from rechallenge in addition to being plasma RAS negative. Trial registration The REMARRY study: UMIN, UMIN000036424 . Registered date: April 5, 2019. The PURSUIT trial: jRCT, jRCTs031190096 . Registered date: October 1, 2019.

Opinion statement Gastric cancer is a heterogenous cancer, which may be classified into several distinct subtypes based on pathology and epidemiology, each with different initiating pathological processes and each possibly having different tumor biology. A classification of gastric cancer should be important to select patients who can benefit from the targeted therapies or to precisely predict prognosis. The Cancer Genome Atlas (TCGA) study collaborated with previous reports regarding subtyping gastric cancer but also proposed a refined classification based on molecular characteristics. The addition of the new molecular classification strategy to a current classical subtyping may be a promising option, particularly stratification by Epstein–Barr virus (EBV) and microsatellite instability (MSI) statuses. According to TCGA study, EBV gastric cancer patients may benefit the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) antibodies or phosphoinositide 3-kinase (PI3K) inhibitors which are now being developed. The discoveries of predictive biomarkers should improve patient care and individualized medicine in the management since the targeted therapies may have the potential to change the landscape of gastric cancer treatment, moreover leading to both better understanding of the heterogeneity and better outcomes. Patient enrichment by predictive biomarkers for new treatment strategies will be critical to improve clinical outcomes. Additionally, liquid biopsies will be able to enable us to monitor in real-time molecular escape mechanism, resulting in better treatment strategies.