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Location: Marriott Marquis
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PQA 07 - PQA 07 Gastrointestinal Cancer and Sarcoma/Cutaneous Tumors Poster Q&A

3037 - Clinical Considerations of Splenic Dose Constraints

Tuesday, October 1, 2024
12:45 PM – 2:00 PM ET
Location: Hall C

Screen: 17

    Presenter(s)

  • Yifu Ma

    The Second Affiliated Hospital of Soochow University
    Suzhou, Jiangsu

Y. Ma, Y. Kong, M. Xu, J. Zhang, P. Xing, J. Qian, and L. Zhang; Center for Cancer Diagnosis and Treatment, The Second Af?liated Hospital of Soochow University, Suzhou, China

Purpose/Objective(s): Lymphocytes, which are highly sensitive to radiation, play a crucial role in the bodys defense against tumors. Radiation-induced lymphopenia has been associated with poorer outcomes in different cancer types. Despite being the largest secondary lymphoid organ, the spleen has not been officially designated as an organ at risk in radiation treatment protocols. This study aimed to provide a reference for splenic dose constraints in the clinical practice of radiotherapy.

Materials/

Methods: To exclude the influence of tumor factors on the radiation dose to the spleen and given the spleens anatomical proximity to the target area for gastric cancer radiotherapy, we selected patients with R0 gastrectomy who underwent adjuvant radiotherapy. A retrospective group of 96 individuals with locally advanced gastric cancer who had undergone postoperative chemoradiotherapy (CRT) between May 2010 and May 2017 was analyzed. Complete blood counts were collected before, during, and after CRT. We conducted a multiple stepwise regression analysis to establish a model for predicting the minimum absolute lymphocyte count (Min ALC) and to investigate potential associations between spleen dosimetric variables and Min ALC.


Results: The median follow-up period was 60 months. The 5-year OS and DFS were 65.2% and 56.8%, respectively. The median values of pre-treatment ALC, Min ALC, and post-treatment ALC were 1.40 * 109/L, 0.23 * 109/L, and 0.28 * 109/L. The median values of ALC decreased by 80% after postoperative CRT. Regression analysis confirmed that the primary tumor location, number of fractions, and spleen V5 were significant predictors of Min ALC during radiation therapy (R2 = 0.298, F = 13.043; p < 0.001). Changes in ALC was identified as an independent predictor of both OS and DFS.


Conclusion: Spleen V5 is an independent predictor for Min ALC, and the maximum dose of the spleen is associated with an increased risk of severe lymphopenia. Meanwhile, changes in ALC can serve as a prognostic indicator for adjuvant radiotherapy in gastric cancer cases. Therefore, we recommend that spleen V5 should be restricted in radiotherapy treatment design.