116P - Spleen as an organ at risk (OAR) in adjuvant chemoradiotherapy of gastric cancer: Retrospective dosimetric single institutional experience

Background

Adjuvant Chemoradiation (CTRT) in Gastric cancer is still commonly practiced in developing countries. During the contouring for Radiotherapy (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. Here through our study we have evaluated the dose of radiation to the spleen in Adjuvant CTRT of Gastric cancer resulting in hyposplenism.

Methods

Between January 2017 to December 2021, 33 patients with histologically proven Adenocarcinoma of Stomach (ACS), non-metastatic who underwent adjuvant CTRT post surgery were considered for the study. Retrospectively patient, tumor and treatment characteristics were retrieved from the medical record archives. Spleen was contoured retrospectively on all CT images that had acquired during the treatment. Dmean (mean dose to spleen) was then estimated. The hematological toxicity was graded according Common Terminology Criteria for Adverse events (CTCAE) version 5. Correlation was done between the Dmean and the development of hematological toxicities using SPSS software version 21.0.

Results

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 2 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.

Conclusions

Through this study we estimated that the Dmean of Spleen should be less than 35Gy to prevent the onset of leukopenia. Spleen should be considered as an important OAR when it comes to Radiation of the Gastric Cancer. However, a larger prospective study with more number of patients and a longer follow up would be required to conclusively confirm the same.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The author.

Funding

Has not received any funding.

Disclosure

The author has declared no conflicts of interest.