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Top Line: Does pretreatment lymphocyte count predict outcomes for oropharyngeal cancer treated with radiation?

The Study: Since the dawn of the immunotherapy era, there have been quite a few studies exploring the relationship between immune cell counts and radiation therapy for various malignancies. This retrospective study from the UK used large discovery (n=791) and validation (n=609) cohorts to explore the prognostic and predictive value of pretreatment absolute lymphocyte count (ALC) in patients receiving radiation or chemoradiation for oropharyngeal squamous cell carcinoma. Patients at one center were treated with 60-66 Gy in 30-33 fractions while patients at another center were treated with 70 Gy in 35 fractions. Two-thirds (67%) of patients in each cohort were p16 positive. Most patients (52% in discovery, 67% in validation) received concurrent cisplatin while 31% in the discovery cohort and 25% in the validation cohort received radiation alone. The remaining minority received either carboplatin or cetuximab. The median ALC was 1.7, and there was no significant difference in ALC according to different characteristics (such as p16 status or receipt of chemo). On multivariable analysis, performance status, smoking status, stage, concurrent chemo, ALC and absolute neutrophil count (ANC) were all associated with 5-year survival. In this model, higher ALC was associated with better outcomes, and that held true for both p16+ and p16- patients. Interestingly, ALC was also predictive of the benefit from concurrent cisplatin. Put another way, there was an interaction between pretreatment ALC and the benefit of concurrent cisplatin such that patients with lower ALCs derived greater benefit from the addition of cisplatin while those with higher ALCs derived less benefit. When dichotomized as ALC low (≤2.4) or high (>2.4), those with low had inferior survival and increased benefit from cisplatin. So, how does this help us in practice? We’re obviously not going to decide who needs chemo based on ALC, but ALC appears to provide important prognostic information. Additionally, a low ALC may cause you to think twice before omitting chemo in a borderline patient.

TBL: Pretreatment absolute lymphocyte count is prognostic of survival in patients receiving radiation for oropharyngeal cancer, and those with low ALC may derive greater survival benefit from concurrent cisplatin. | Price, J Clin Oncol 2022