ESTRO 2023 - Abstract Book

S66

Saturday 13 May

ESTRO 2023

Results In this study 689 of 788 patients (87%) in the CRITICS study were included. A four-cluster model with four distinct clusters (i.e. mild toxicity (blue), neutropenia toxicity (green), poly toxicity (red), and gastrointestinal toxicity (orange)) had the best model fit (Figure 1). The percentage of patients completing the preoperative treatment was highest in the neutropenia toxicity cluster (95%) and lowest in the poly toxicity cluster (76%; p=0.003). Membership of the different clusters was significantly associated with OS: patients in the neutropenia toxicity cluster had the longest median OS, with 58 months (95% confidence interval (CI) 22-93) while patients within the gastrointestinal toxicity cluster had the shortest median OS of 22 months (95% CI 6-38; p=0.005). This was also observed for EFS, where the neutropenia toxicity cluster had the longest median EFS of 44 months (95% CI 1-87) compared to 13 months (95% CI 8-18) in the gastrointestinal toxicity cluster (p=0.018).

Conclusion In patients with locally advanced gastric cancer and treated in the CRITICS trial, we identified four distinct toxicity clusters during preoperative chemotherapy. Membership of the different clusters was highly prognostic for both EFS and OS, with very large differences between clusters and patients in the neutropenia toxicity cluster having the best EFS and OS. Therefore, this novel approach in which we identified distinct toxicity clusters already during the first chemotherapy course, could potentially play a role in clinical and shared decision-making during this intense treatment.

Proffered Papers: Head & neck

OC-0105 Incidence and survival after HPV+ and HPV- oropharynx cancer in Denmark 1986-2020 - A DAHANCA study P. Lassen 1,2 , J. Alsner 3 , C. Andrup Kristensen 4 , E. Andersen 5 , H. Primdahl 2 , J. Johansen 6 , M. Andersen 7 , M. Fahardi 8 , J. Grau Eriksen 3 , M. Halgren olsen 9 , J. Overgaard 3 1 Aarhus University Hospital, Experimental Clinical Oncology , Aarhus, Denmark; 2 Aarhus University Hospital, Oncology, Aarhus, Denmark; 3 Aarhus University Hospital, Experimental Clinical Oncology, Aarhus, Denmark; 4 Rigshospitalet, Copenhagen University Hospital, Oncology, Copenhagen, Denmark; 5 Herlev Hospital, Copenhagen University, Oncology, Herlev, Denmark; 6 Odense University Hospital, Oncology, Odense, Denmark; 7 Aalborg University Hospital, Oncology, Aalborg, Denmark; 8 Næstved Hospital, Oncology, Næstved, Denmark; 9 Danish Cancer Society, Danish Cancer Society, Copenhagen, Denmark Purpose or Objective To describe the incidence and overall survival (OS) after oropharyngeal carcinoma (OPC), including the relation to Human Papillomavirus (HPV), in a Danish population-based cohort of consecutive patients diagnosed between 1986-2020. Materials and Methods The study cohort was identified in the Danish Head and Neck Cancer database, which has 100% coverage of OPC in Denmark. Data on consecutive Danish patients living in Denmark at the time of OPC diagnosis was prospectively collected and verified in the Danish Cancer Registry. Primary treatment was radiotherapy (66-68 Gy) according to national guidelines with a gradual introduction of radiobiological modifications based on the findings from clinical trials, ie. hypoxic modification and moderately accelerated fractionation in the beginning of the period, and from 2008 concurrent chemoradiotherapy. Tumor HPV-status was determined on pre-treatment tumor tissue according to p16 immunohistochemistry (p16pos>70% tumor cells). Results A total of 8595 patients with stage I-IV OPC were identified, 6324 (74%) men and 2271 (24%) women, with a median age of 60 years. p16-positivity was found in 3530 (41%) of the tumors, whereas 2362 (28%) were p16- and 2703 (31%) had unknown p16-status. Seventy % of patients in the p16+ subgroup were ever smokers (25% current smokers) compared to 97% (71% current smokers) with p16- tumors. During the 35-year time period a threefold increase in the incidence of OPC was observed for both men and women. Simultaneously the frequency of HPV-related p16-positivity among tumors with known p16-status (N=5892) increased from 30% to 70% (Figure 1A). The yearly number of new cases of p16- tumors also increased over time although not to the same extent. The 5-year OS probability was 53% in the total cohort, and stratification by p16-status revealed a marked survival benefit in favor of p16-positivity: 76% vs 34% (39% in tumors with unknown p16-status) (Figure 1B). Figure 2 demonstrates the