Sugihara, Kenichi

e15557 Background: In metastatic colorectal cancer (mCRC), systemic chemotherapy can enable conversion surgery in a subset of patients with initially unresectable disease. Although R0 resection considered a key determinant of long-term survival, its clinical impact across heterogeneous trial populations and treatment strategies remains insufficiently defined. We aimed to clarify the survival benefit of R0 resection after first-line chemotherapy using large-scale individual patient data. Methods: Using the ARCAD database, which comprises 67 randomized clinical trials and approximately 47,000 patients, we conducted a pooled analysis of individual patient data from six first-line randomized clinical trials (COIN, COIN-B, 03-TTD-01, ATOM, SOFT and PARADIGM) for which data on R0 resection were available. Patients with initially unresectable mCRC and available surgical data were categorized into three groups: R0 resection, non-R0 resection, and no surgery. All R0 cases were included, comprising liver-only, lung-only, combined liver and lung metastases, and peritoneal dissemination or other metastatic sites. Overall survival (OS) and progression-free survival (PFS) were evaluated using multivariable Cox proportional hazards models adjusted for age, sex, and performance status. Pre-specified subgroup analyses examined the consistency of outcomes according to tumor response, metastatic site, primary tumor sidedness, RAS status, and targeted therapy class. Results: Among 4,445 eligible patients, 263 underwent R0 , 233 underwent non-R0 resection, and 3,949 received no surgical intervention. The R0 resection group comprised patients with liver-only metastases (n = 176), lung-only metastases (n = 23), and combined liver and lung metastases (n = 27). R0 resection was associated with significantly improved OS and PFS compared with both non-R0 resection and no surgery. These survival benefits were consistently observed across key clinical subgroups, including patients achieving complete or partial response to chemotherapy, those with liver or lung metastases, left- and right-sided primary tumors, and both RAS wild-type and mutant disease. Importantly, the benefit of R0 resection was maintained irrespective of anti-EGFR– or anti-VEGF–based first-line therapy. Conclusions: R0 resection following systemic chemotherapy is strongly associated with durable survival benefits in patients with initially unresectable mCRC across diverse clinical settings. These findings support the pivotal role of conversion strategies and highlight the importance of multidisciplinary evaluation to identify appropriate candidates for curative-intent resection.

BACKGROUND: Data registries lack a definitive classification system that distinguishes different locations of colon cancer from one another. OBJECTIVE: To establish an international consensus on the definition of primary colon cancer segment locations. DESIGN: Between December 2022 and June 2023, Delphi survey study was conducted to seek opinions from relevant international experts and eventually develop a consensus definition of each colon cancer segment. SETTING: Three-round online-based Delphi survey study. INTERVENTIONS: Online survey included 17 questions. In the first two rounds, participating experts were asked to rank each statement on a scale of 1–9 (9 is the most relevant). Consensus statements and definitions were revised according to results, obtaining a consensus score of 7–9. During the third round and online meeting, definitions and statements reached a moderate or high consensus(above 4 in more than 70% of participants) were included. MAIN OUTCOME AND MEASURE: Primary goal of our project was focused on precisely localizing the specific segment affected by primary colon cancer, rather than to identify surgical treatment or type of resection needed for particular segment. RESULTS: The first round included 331 experts, 301 (91%) completed the second round, and 295 (98%) completed the final round. Experts strongly supported the use of a “10 cm rule” to describe colon cancer sites at the flexures and anatomical landmarks for other segments. Regarding the definition of rectosigmoid cancer, experts from America and Europe reached a high consensus that the term rectosigmoid as a colon cancer location must be abolished in contrast to experts from Asia. Description of cancers overlapping segments achieved a consensus of 64%. LIMITATIONS: Subjective decisions are based on individual expert clinical experience. CONCLUSIONS: This Delphi survey, the first internationally conducted consensus study, achieved a remarkable level of consensus among a panel of global experts. Ambiguity still exists regarding overlapping lesions. See Video Abstract .