(Tuesday, 7/14/2020) 1:00 PM - 3:00 PM [Eastern Time (GMT-4)]
Room: Track 2
Purpose: The peripheral lymphocyte-monocyte ratio (LMR) is a prognostic immune biomarker for predicting tumor response of chemoradiotherapy (CRT) of multiple cancers. The role of LMR is still unknown for pelvic regional cancer since the irradiation of large areas of pelvic bone marrows may cause leukopenia and other hematological toxicity. This study aims to evaluate whether the peripheral LMR is associated with tumor response when bone marrows is inevitably irradiated in anal cancer patients.
Methods: Twenty anal cancer patients treated with CRT with pre- and post- PET images between 2011-2017 were identified. Blood cell counts including weekly lymphocyte and monocyte were recorded. The LMR was calculated as the ratio of absolute counts of lymphocytes and monocytes. The primary tumor response was evaluated by comparing mean standard uptake value (SUV) before and after CRT. Pelvic bones were contoured on PET-CT scans, and active bone marrow (ABM) was defined as the subvolume of the total BM having SUV higher than the mean uptake of unirradiated extrapelvic BM. Pearson's coefficients and p-values were calculated among LMR, ABM, and mean SUVtumor. A general linear regression model of pre-CRT LMR is used to predict tumor response.
Results: The mean LMRs were 3.01 and 1.36 for pre- and post-CRT(t-test,p=0.041). The mean ABMs were 55.8% and 34.9% for pre- and post-CRT(p<0.0001), meanwhile the SUVtumor is 3.86 and 2.15(p=0.005). Our results show that LMR is only significantly correlated with ABM at pre-treatment(p=0.0135) not at post-treatment(p=0.303). LMR is significantly associated with primary tumor SUV both before and after treatment(p=0.0381, 0.0336, respectively). A general linear regression shows that the pre-CRT LMR predicted treatment response with p=0.036.
Conclusion: The LMR is a significant biomarker correlated with tumor response in anal cancer chemoradiotherapy. Pre-treatment LMR and PET images can be used to predict CRT response toward dose reduction and bone marrow sparing radiotherapy.
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