C reactive protein/Albumin ratio as predictor of prognosis in castration resistant metastatic prostate cancer

Objective: To assess the association of C reactive protein/Albumin ratio (CAR) with progression free survival (PFS) and overall survival (OS) in castration resistant metastatic prostate cancer (mCRPC) patients. Materials and methods: A transversal study was conducted, including all patients diagnosed with mCRPC within a Central Hospital Urological Oncology consultation between December 2019 and December 2021 (n = 178) and that were submitted to systemic therapy. CRP and albumin results were collected at the beginning of the systemic treatment for mCRPC in 103 patients and, in 75 patients already under treatment at the start of the study, on that occasion (December 2019). All patients were then followed. CAR was correlated with PFS and OS. OS and PFS were measured from the day the CRP and Alb were collected until the event of interest or the final date of follow-up. The sample was divided in two groups according to an optimal cutoff point found in a ROC curve. Results: The sample showed a median age of 75.76 ± 9.17 years old. Using a cut-off point of 0.22, patients with a CAR ≤ 0.22 (63.2%) showed, compared to CAR > 0.22, longer PFS (15.92 vs. 9.46 months, r = -0.13, p < 0.05) and OS (p = < 0.05, 25,72 vs. 15.79 months, r = -0,24, p < 0.05). Better OS in patients with CAR ≤ 0.22 vs > 0.22 was detected on both the group evaluated at the beginning of systemic treatment (26.96 vs 17.63 months, p < 0.05) and the group of patients already under treatment (23.90 vs 11.54 months, p < 0.05). Dividing the sample according to the first line treatment chosen, we found OS of 26.25 vs 5.9 months (p < 0.05), 27.71 vs 22.57 months (p < 0.05) and 27.36 vs 23.75 months (p = 0.12), for docetaxel, abiraterone and enzalutamide, respectively. Conclusions: According to this study, higher values of CAR are associated with lower PFS and OS in mCRPC patients. We found a cut-off value of 0.22 providing the best discrimination for prognosis. CAR is a good prognosis biomarker, irrespective of the moment of evaluation and chosen treatment option.