ESTRO 2024 - Abstract Book

S2190

Clinical - Upper GI

ESTRO 2024

2021 and August 2023. Patient with mixed photon/proton treatment or insufficient lymphocyte data (no absolute lymphocyte count (ALC) in the last two weeks of treatment) were excluded from analysis. The primary endpoint was grade IV RIL (ALC<0.2, according to CTCAE v5.0) within two weeks after treatment. A multivariable logistic regression analysis with backward selection was performed to identify predictors for grade IV RIL.

Results:

A total of 233 oesophageal cancer patients were selected for this analysis. Patient characteristics, comparing nCRT to dCRT, are listed in Table 1. The overall incidence of grade IV RIL was 19% (43/233) and was more frequently observed after dCRT, compared to nCRT; 41% vs 11%. After nCRT, the incidence of grade IV RIL increased over the weeks of treatment; 6% (4th week), 10% (5th week) or 11% (after treatment). A comparable increase was seen after dCRT; 7% (4th week), 18% (5th week), 34% (6th week), and 41% (after treatment). Multivariable logistic regression analysis indicated baseline ALC (OR:0.21, 95CI: 0.09-0.49), PTV (per dL) (OR: 1.54, 95%CI: 1.27-1.87), radiotherapy (RT) technique (proton RT vs photon RT) (OR: 0.27, 95%CI: 0.11-0.67) and treatment regimen (23 fractions (nCRT) vs 28 fractions (dCRT)) (OR: 6.9, 95%CI: 2.81-16.79) to be independent predictors for grade IV RIL. RT technique could be replaced by mean heart dose (MHD) (OR: 1.11, 95%CI: 1.04-1.20), with minimal effect on the other predictors in the model, including treatment regimen.

Conclusion:

The treatment regimen was an independent predictor for lymphopenia grade IV, next to baseline ALC, PTV and MHD (or RT technique). Next to the total dose, this might be explained by the differences in the number of fractions. Hypofractionation, reducing the number of fractions without decreasing the total dose, might be a way to decrease the risk of severe lymphopenia, and consequently improved survival of esophageal cancer patients.