Red cell differential width (RDW) as a predictor of survival outcomes with palliative and adjuvant chemotherapy for metastatic penile cancer.

Purpose: Red cell distribution width (RDW) measures red cells' size variability. Metastatic penile cancer displays poor chemotherapy response. As no validated prognostic predictor exists, we investigated whether RDW correlates independently with survival outcomes in metastatic penile cancer treated by chemotherapy.
Methods: Electronic chemotherapy files of patients with metastatic penile cancer (M1 or N3) from a large academic supra-regional centre were retrospectively analysed between 2005 and 2018. Patients were stratified into RDW > 13.9% and < 13.9%, as per published data on RDW in renal cell carcinoma. Survival time was calculated from the date of chemotherapy initiation until the date of death.
Results: 58 patients were analysed. The RDW-high group (n = 31) had a poorer survival than the RDW-low group (n = 27). Median overall survival (mOS) in all patients was 19.0 months (95% CI 13.1-24.9). mOS for RDW-high was 15.0 months (95% CI 10.1-19.9) and 37.0 months (95% CI 32.3-43.1) for RDW-low. Kaplan-Meier curves showed a clear disparity in survival (log rank p = 0.025). Cox proportional hazard ratio for death, corrected for T-stage, grade, age and deprivation score was 0.43 (p = 0.04). Sub-analysis of the M1 patients showed mOS in RDW-high of 17 m (95% CI 11.6-22.4) vs. NR; HR for death of 0.42. N3 patients' mOS in RDW-high cohort was 30 months (95% CI 4.5-55.9) vs. 13 months (95% CI 1.8-24.2) in RDW-low; HR for death was 0.30.
Conclusion: RDW correlates independently with survival outcomes in metastatic penile cancer and may act as a potential predictor of survival outcomes for patients with metastatic penile cancer receiving chemotherapy.