Objective : In this study, we report changes in neutrophil-to-lymphocyte ratio (NLR) after cryoablation of renal cell carcinoma (RCC) osseous metastases, with consideration of concomitant nivolumab and ablation margins as confounding variables. As a basic surrogate for systemic tumor immunity, increased NLR has been associated with decreased response to immune checkpoint inhibitor therapy. Should cryoablation affect NLR, then treatment may modulate nivolumab immunotherapy treatment.
Methods : Single institution retrospective analysis of adult patients (age>18 years) treated with cryoablation of RCC osseous metastases from December 2015 to September 2018. Patients were include if NLR could be calculated from existing blood labs drawn within 1 month before and up to 6 months after cryoablation. NLR obtained within 1 week of documented infection were excluded. Average baseline NLR from 1 month pre-cryoablation was compared to average NLR obtained 1 week, 1 month, and 6 months after cryoablation, with correlation to nivolumab administration within 2 weeks.
Results : Of 22 patients (18:4 M:F, mean age 60) included with post-cryoablation NLR within 6 months, post-cryoablation NLR was obtained within 1-week in 11 and within 1-month in 16. Average size of ablated lesion was 4.9 cm, with cryoablation performed to completion (>5 mm margins) in 11 patients (50%). Post-cryoablation, an NLR increase was seen at 1 week in 10/11 patients (91%), at 1 month in 10/16 patients (62.5%), and at 6 months in 11/22 (50%) with mean increase from 3.5 to 5.2, 4.3, 4.6 respectively. Neither administration of nivolumab within 2 weeks of cryoablation nor complete ablation margins were significant confounding variables.
Conclusions : Cryoablation of RCC osseous metastases may result in a transient mild increase in NLR, suggesting cryoablation in this patient population transiently decrease potency of immune checkpoint inhibitor therapy particulately within a week of cryoablation. Further evaluation with specific inflammatory markers is needed to confirm results and guide therapy timing.