e16055 Background: The addition of anti-PD-1 antibodies to first-line CT is the new standard of care for pts with advanced EC. However, available data on the efficacy of such therapy in different clinical subgroups is still lacking. Therefore, we performed a meta-analysis to determine the efficacy of combination anti-PD1 and systemic CT in terms of overall survival (OS) in pts with advanced EC. Methods: We searched PubMed, proceedings of ASCO, and ESMO conferences up to February 2022. We included prospective randomized phase III trials comparing the combination of anti-PD1 and CT with CT alone as the first-line treatment option for pts with advanced EC. The primary outcome was OS. Meta-analysis was conducted by Review Manager (Ver. 5.3) software. Results: Five trials with a total of 3163 pts were included, of which 1576 received anti-PD1+CT and 1587 received CT alone. There was a significant improvement in PFS (HR, 0.62; 95% CI, 0.56-0.67; p < 0.00001; I2 = 45%, p for heterogeneity 0.12), OS (HR, 0.69; 95% CI, 0.63-0.76; p < 0.00001; I2 = 0%) and ORR (OR, 2.07; 95% CI, 1.76-2.43; p < 0.00001; I2 = 21%) in pts received anti-PD1+CT. OS was improved in pts regardless of age, race, CT regimen, presence of liver metastases, ECOG PS, or histology. Subgroup analysis suggested that the addition of anti-PD1 have a better effect in pts with PDL expression on tumor cells > 1, ≥ 10, and < 10 and in pts with CPS ≥ 10, but not in pts with PDL < 1. We found a tendency towards survival advantage in pts with CPS < 10. No survival benefit was observed in women (tab). Conclusions: Improved OS was found to be associated with addition of anti-PD1 antibodies to systemic CT in different patient subgroups with advanced EC, except for female and in pts with low PDL expression. Despite of meta-analysis results we need prospective randomized trial for pts with CPS < 10.[Table: see text]

e15608 Background: in 2021 ASCO has updated guidelines on adjuvant therapy for stage II colon cancer with the statement: “Patients with T4 tumors are at higher risk of recurrence and should be offered adjuvant chemotherapy, whereas patients with other high-risk factors, including sampling of fewer than 12 lymph nodes in the surgical specimen, perineural or lymphatic invasion, poorly or undifferentiated tumor grade, intestinal obstruction, tumor perforation, or grade BD3 tumor budding, may be offered ACT”. We performed a single-center retrospective study to assess the prognostic role of postoperative tumor stage T4 and T3 with ≥2 negative prognostic factors in patients with resected stage II colon cancer. Methods: We retrospectively analyzed 1457 pts with stage I-III colon cancer treated in Russian Cancer Research Center n.a. N.N. Blokhin from 2001 to 2015. We included pts with resected stage II colon cancer with following negative prognostic factors: T4; sampling of fewer than 12 lymph nodes in the surgical specimen; perineural or lymphatic invasion; poorly or undifferentiated tumor grade; intestinal obstruction; and tumor perforation. Three cohorts were studied: pts with pT4N0M0 with no other high-risk factors (group A), pts with pT4N0M0 with additional high-risk factors (group B), and pts with pT3N0M0 with ≥2 high-risk factors (group C). The primary study endpoint was 3-year disease-free survival (DFS). The secondary endpoint was 5-year overall survival (OS). Statistical analysis was done with SPSS v.20. Results: 164 pts met the inclusion criteria with 17 (10%) pts in group A, 90 (55%) pts in group B, and 57 (35%) pts in group C. Adjuvant chemotherapy was performed in 8 (47%), 25 (28%), and 9 (16%) pts, respectively (p = 0.035). At a median follow-up of 62 months (range, 2-135 months), the 3-year DFS was 82%, 68%, and 78% for groups A, B, and C, respectively (HR, 1.55; 95% CI, 0.99-2.4; p = 0.053). No difference in 3-year DFS was found between group A and C (HR, 1.0; 95% CI, 0.34-3.2; p = 0.9). The 5-year OS was 75%, 65%, and 78% for groups A, B, and C, respectively (HR, 1.38; 95% CI, 0.84-2.3; p = 0.2). Conclusions: Patients with pT4 with additional high-risk features had worse overall survival compared to other subgroups with resected stage II colon cancer. There was no difference in survival rates between patients with pT4 with no additional negative prognostic factors and pT3 with ≥2 negative prognostic factors. Therefore, we propose that patients with pT4 as well as with pT3 with ≥2 negative prognostic factors are at a higher risk of recurrence and should be offered adjuvant chemotherapy.