Spleen as an Organ at Risk (OAR) in Adjuvant Chemoradiotherapy of Gastric Cancer-Retrospective Dosimetric Single Institutional Experience

Abstract

<h3>Purpose/Objective(s)</h3> Adjuvant Chemoradiation (CTRT) in Gastric cancer is still commonly practiced in developing countries. Contouring for RT in a Gastric cancer there are various structures, which are considered as Organs at risk (OAR). However, there are no published literature evidence for the dose constraints for Spleen. Spleen plays a huge role in adaptive immune responses and clears pathogens from circulation. Radiation to spleen is known to cause hyposplenism. There are no literature evidences to determine what the safe dose of radiation to spleen are. Here in our study, we are trying to evaluate the dose of radiation to the spleen in Adjuvant CTRT of Gastric cancer. <h3>Materials/Methods</h3> Between January 2017 to December 2021, 33 patients with histologically proven Adenocarcinoma of Stomach (ACS), non-metastatic who underwent adjuvant CTRT were considered for this study. Retrospectively patient, tumor and treatment characteristics were retrieved. Spleen was contoured retrospectively on all CT images acquired. Dmean (mean dose to spleen) was documented retrospectively. The hematological toxicity was graded according to Common Terminology Criteria for Adverse events (CTCAE) version 5. <h3>Results</h3> The mean age was calculated to be 60 years. 79% (27 patients) of our patients were males and 21% (7 patients) females. All patients completed the planned RT dose of 45Gy in 25 fractions. The mean spleen volume was calculated to be 186.65cc (Range 90cc -303cc). The mean RT dose to spleen was calculated to be 35.35 Gy (Range 20 Gy to 42Gy). Leukopenia grade 3 was seen in 82%, grade 3 in 67%, grade 4 in 15%. Thrombocytopenia Grade 2 in 73%, grade 3 in 41%. ROC curve was generated and found that a Dmean spleen dose of above 35Gy resulted in Grade 3 and above Leukopenia. <h3>Conclusion</h3> Spleen should be considered as an important OAR when it comes to Radiation of the Gastric Cancer. We conclude in our study that a Dmean of Spleen should be less than 35Gy to prevent the onset of leukopenia. However, a larger prospective study with a greater number of patients and a longer follow up would be required to confirm the same.