ESTRO 2024 - Abstract Book

S1567

Clinical - Lower GI

ESTRO 2024

Society of Medical Oncology (ESMO) [1]. The aim of this study is to evaluate the impact of adherence to 2017 ESMO guidelines on survival outcomes in rectal cancer Real World patient Data.

Material/Methods:

A retrospective approach was used to analyse patients treated between December 2000 and 2021. Patients were stratified based on their initial clinical staging into early, intermediate, locally advanced, and advanced risk groups according to the 2017 ESMO guidelines. Each risk category corresponds to specific treatment recommendations. Using process mining techniques, patients were categorised as adherent or non-adherent according to ESMO classifications. Deviations from the ESMO guidelines were classified as overtreatment or undertreatment. Overtreated patients received radiotherapy (RT) doses beyond ESMO guidelines (RT≥55Gy) or a chemotherapy (CT) intensification with oxaliplatin, a drug not included in the ESMO guidelines. Undertreated patients received RT doses below the ESMO guidelines dose (RT<45Gy).

Clinical impact of adherence and non-adherence to ESMO guidelines was assessed using survival outcomes such as overall survival (OS), disease-free survival (DFS), local control (LC), metastasis-free survival (MFS).

Results:

Overall, 2219 rectal cancer patients were identified from 2000 to 2021: 140 (6.3%), 279 (12,6%), 1084 (48.8%) and 716 (32.3%) were early, intermediate, locally advanced and advanced, respectively.

The overall adherence to ESMO guidelines was 14.1%, 25 (17.85%), 39 (14%) 195 (18%) and 55 (7.7%) early, intermediate, locally advanced and advanced patients were adherent, respectively.

Table 1 shows the outcomes results for the different risk classes (Table 1), comparing adherent to not adherent to ESMO Guidelines patients.

No significant differences were observed in survival outcome for the early risk group.

In the intermediate risk group, the 5years-OS (5yOS) significantly improved with overtreatment: 85.9% and 86.8% for increased RT dose and oxaliplatin-CT, respectively (p<0.01).

For locally advanced patients, adherent patients had a 5yOS of 74.9%, while non-adherent patients achieved notably higher 5yOS at 87.1% and 86.9% with RT overdosage and oxaliplatin-CT, respectively (p<0.001). In the advanced risk group, 5yOS improved with RT dose overtreatment(p<0.001). In the intermediate non-adherent risk group, 5years-DFS (5yDFS) improved with increased RT doses (72.1% p<0.003) and oxaliplatin-CT (76.4% p<0.01). Locally advanced 5yDFS was 72.9% with escalated RT doses (p<0.005) and 78% with oxaliplatin-CT (p<0.001). In the advanced risk group, overtreatment with RT dose significantly improved 5yDFS (p<0.001). In terms of 5-year-MFS (5yMFS), non–adherent intermediate and locally advanced groups benefited from oxaliplatin-CT, with rates of 86% and 85.9%, respectively (p<0.019 and p<0.028). No significant 5yMFS difference was observed in the advanced risk group. Regarding the 5years-LC (5yLC), the non-adherent intermediate group showed better results with RT doses, at 93.8% (p<0.048). Locally advanced patients benefited from oxaliplatin-CT at 95.6% (p<0.001). In the advanced risk group, the 5yLC was exclusively related to variations in the RT dose (p<0.007).