ESTRO 2022 - Abstract Book

S1101

Abstract book

ESTRO 2022

Conclusion SMI loss ≥ 7% after SBRT is a significant prognostic factor for worse survival and is associated with liver toxicity compared with pre-SBRTsarcopenia.

PO-1306 Impacts and consequences of spleen irradiation after adjuvant chemoradiation for stomach cancer

S.F. Lee 1,2 , P.L. Yip 3 , A. Wong 3 , F. Ng 2 , V. Koh 4 , L.C. Wong 4 , F.A.S. Lee 2 , H. Mamon 5

1 University of Hong Kong, Department of Clinical Oncology, Hong Kong, Hong Kong (SAR) China; 2 Tuen Mun Hospital, Department of Clinical Oncology, Hong Kong, Hong Kong (SAR) China; 3 Tuen Mun Hospital, Department of Clinical Oncology, Hong Kong, Hong Kong (SAR) China; 4 National University Cancer Institute, Department of Radiation Oncology, Singapore, Singapore; 5 Dana-Farber/Brigham and Women's Cancer Center, Harvard Medical School, Department of Radiation Oncology, Boston, Massachusetts, USA Purpose or Objective To determine whether severity of lymphopenia is associated with the dose-volume histogram (DVH) parameters of the spleen irradiated unintentionally during adjuvant chemoradiation (CRT) in patients with gastric cancer. Materials and Methods Patients who received adjuvant chemoradiation for gastric cancer from January 2015 to December 2020 were analyzed. The splenic DVH parameters were reported as mean splenic dose (MSD) and percentage of splenic volume receiving at least x Gray (Gy). Peripheral blood counts were recorded at baseline and after CRT. The development of severe post-CRT lymphopenia (absolute lymphocyte count [ALC] <0.5 K/µL) was assessed by multivariable logistic regression with use of patient and dosimetric factors. Overall survival (OS), recurrence-free survival (RFS), and cumulative incidence of infectious events were estimated and analyzed with the use of stepwise Cox model or competing risk analysis as appropriate. Results We analyzed 84 patients, with median follow-up duration of 42 months. The median baseline ALC and post-CRT ALC were 1.9 K/µL (range, 0.7–2.8 K/µL) and 0.9 K/µL (range, 0.0–4.9 K/µL), respectively (P < 0.001). MSD > 40 Gy (odd ratio [OR], 3.81; 95% confidence interval [CI], 1.15–12.60; P = 0.028), high baseline neutrophil-to-lymphocyte ratio (OR per 1 unit increase, 2.13; 95% CI, 1.02–4.41; P = 0.043), and sex (OR for male to female, 0.34; 95% CI, 0.12–0.97; P = 0.043) were associated with the development of severe post-CRT lymphopenia, which was a risk factor for poorer OS (hazard ratio [HR], 2.27; 95% CI, 1.13–4.58; P = 0.022) and RFS (HR, 2.21; 95% CI, 1.13–4.32; P = 0.021). The cumulative incidence of infections was higher among patients with severe post-CRT lymphopenia (2.53, 95% CI, 1.03–6.23, P = 0.043).