Introduction: Lymphocytes are the main effector cells that promote responsiveness to cancer immunotherapy. We were the first to show that earlier time-of-day immunotherapy for metastatic melanoma is associated with longer progression-free and overall survival1, potentially due to better synchronization of adaptive immune stimulation and oscillating T lymphocytes in the lymphovascular space2–4. In this study, we examined time-of-day variation of circulating lymphocytes in patients with melanoma to guide treatment times for a planned randomized controlled trial (RCT) of earlier vs. later infusion of immunotherapy.
Methods: In the UK Biobank5, we identified participants at enrollment who had (A) an active diagnosis of melanoma, (B) overlapping comorbidities with group A but no diagnosis of melanoma, or (C) no documented diagnoses, using linked ICD9/10 codes. For each group, time-of-day of blood collection at enrollment and corresponding absolute lymphocyte count (ALC) were fitted to cosinor models to detect differences in amplitude, acrophase, and midline-estimating statistic of rhythm (MESOR) for daily ALC variation.
Results: There were 329,710 subjects (Table6) who met study eligibility. Compared to healthy subjects in group C, those in groups A and B were more likely to be female, older, obese, former smokers, and members of lower income households (P<0.0001). Sleep duration and temporal distributions of blood collection did not differ among groups (P>0.05). While estimated amplitudes and times of peak ALC (2:30–2:40) were similar across groups (P>0.05), subjects with melanoma had higher MESOR of ALC than healthy subjects (2020 vs. 1960/μL, P=0.019).
Conclusions: Using spot measurements from a large population-based cohort study, we replicated the rhythmicity of circulating lymphocytes in healthy individuals demonstrated by previous serial blood measurements7. Moreover, phase and amplitude of lymphocyte oscillation appear unaffected by melanoma diagnosis. For patients with melanoma, these findings support the design of RCTs that test immunotherapy administration during the early morning vs. late afternoon.