Absolute Lymphocyte Count Predicts Abscopal Responses and Outcomes in Patients Receiving Combined Immunotherapy and Radiotherapy: A prospective-retrospective analysis of 3 phase I/II Trials.

Absolute Lymphocyte Count Predicts Abscopal Responses and Outcomes in Patients Receiving Combined Immunotherapy and Radiotherapy: A prospective-retrospective analysis of 3 phase I/II Trials.:

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Absolute Lymphocyte Count Predicts Abscopal Responses and Outcomes in Patients Receiving Combined Immunotherapy and Radiotherapy: A prospective-retrospective analysis of 3 phase I/II Trials.

Int J Radiat Oncol Biol Phys. 2020 Feb 06;:

Authors: Chen D, Verma V, Patel RR, Barsoumian HB, Cortez MA, Welsh JW

Abstract

BACKGROUND: Research to elucidate predictive factors of the abscopal effect is an essential first step toward potentially modifying these factors to increase the incidence of systemic anti-tumor effects. This study, utilizing data from three institutional phase I/II trials, examined the predictive capacity of recorded parameters in patients undergoing combined radiotherapy (RT) and immunotherapy and explored outcomes based on those predictive factors.

METHODS: All patients underwent combined immunotherapy and RT and had at least one nonirradiated noncontiguous lesion to evaluate out-of-field (abscopal) responses, defined as the best RECIST response.

RESULTS: Altogether, 153 patients met the study criteria, and the median follow-up was 21.1 months. The most common cancer types were NSCLC (n=62), SCLC (n=25), head/neck cancers (n=16), and renal cell carcinoma (n=13). Immunotherapies included ipilimumab (n=98) or pembrolizumab (n=55). Multivariable linear regression indicated that post-RT ALC, when analyzed as a continuous variable, correlated with abscopal responses (p<0.001). For post-RT absolute lymphocyte count (ALC), the abscopal response rate was 34.2% in the cohort with ALC higher than the median value, compared to 3.9% in patients with ALC lower than the median (P<0.0001). Corresponding figures for pre-RT ALC were 30.3% vs. 7.8%, respectively (P=0.0004). Cox multivariate analysis confirmed that lower post-RT ALC also associated with poorer PFS (p=0.009) and OS (p=0.026).

CONCLUSION: Lymphopenia, measured as the continuous variable of post-RT ALC, may impact the occurrence of abscopal responses and thus influence prognosis in patients treated with RT and immunotherapy. Although this hypothesis-generating finding requires corroboration by additional data, it suggests the importance of ALC monitoring and the potential of therapeutic manipulation of this parameter to induce abscopal effects.

PMID: 32036004 [PubMed - as supplied by publisher]