Chemoradiation-related lymphopenia and its association with survival in patients with anal cancer.

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3 Background: While treatment-related lymphopenia (TRL) is common and associated with poorer survival in multiple solid malignancies, little data exists for anal cancer. We evaluated TRL and its association with survival in anal cancer patients treated with chemoradiation (CRT). Methods: A retrospective analysis of 140 patients with non-metastatic anal squamous cell carcinoma (SCC) treated with definitive CRT was performed. Total lymphocyte counts (TLC) at baseline and monthly intervals up to 12 months after initiating CRT were analyzed. Multivariable Cox regression analysis was performed to evaluate the association between overall survival (OS) and TRL, dichotomized by G4 TRL ( < 0.2k/μl) two months after initiating CRT. Kaplan-Meier and log-rank tests were used to compare OS between patients with versus without G4 TRL. Results: Median time of follow-up was 55 months. Prior to CRT, 95% of patients had a normal TLC ( > 1k/μl). Two months after initiating CRT, there was a median of 71% reduction in TLC from baseline and 84% of patients had TRL: 11% G1, 31% G2, 34% G3, and 8% G4. On multivariable Cox model, G4 TRL at two months was associated with a 3.7-fold increased risk of death (p = 0.013). On log-rank test, the 5-year OS rate was shorter in the cohort with versus without G4 TRL at two months (32% vs. 86%, p < 0.001). Conclusions: TRL is common and may be another prognostic marker of OS in anal cancer patients treated with CRT. The association between TRL and OS supports the hypothesis that host immunity plays an important role in survival among patients with anal cancer. These results support ongoing efforts of randomized trials underway to evaluate the potential role of immunotherapy in localized anal cancer.