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Radiotherapy remains the mainstay treatment for the majority of patients diagnosed with cancer. Lymphopenia, a drop in circulating lymphocyte counts part of white blood cells, usually occurs after treatment of cancer with radiotherapy either alone or with chemotherapy. Radiation induced lymphopenia can have an adverse effect on the treatment outcome of patients with various tumor types and negatively affect patients’ survival. Lymphopenia happens when circulating lymphocyte counts, lymphoid tissue, and bone marrow are being irradiated (1, 2). The severity of lymphopenia has been correlated with the integral dose to the body, the dose to the heart and lung, and the dose received by the bone marrow. A reduction in dose received by these structures can be achieved using proton therapy due to the favourable depth-dose characteristics of protons, substantially reducing the volumes of healthy tissues being irradiated specially to medium and low dose. This potentially would lead to sparing lymphocyte counts and mitigating lymphopenia. This presentation will give an overview on the current evidence on the expected gain in sparing lymphocyte counts using protons compared with photons.



1.    Abravan A, Faivre-Finn C, Kennedy J, McWilliam A, van Herk M. Radiotherapy-Related Lymphopenia Affects Overall Survival in Patients With Lung Cancer. Journal of Thoracic Oncology. 2020;15(10):1624-35.

2.    Abravan A, Vasquez Osorio E, Green A, McPartlin A, van Herk M. Anatomical Association of Dose Distribution With Radiotherapy-Related Lymphopenia in Oropharynx Cancer. International Journal of Radiation Oncology*Biology*Physics. 2021;111(3, Supplement):e419.