Objective  To evaluate the prognostic value of serum phosphorus level in castration- refractory prostate cancer (CRPC).

  Methods  The clinical data of 56 patients with CRPC who were admitted to the Second Hospital of Tianjin Medical University between January 2009 and January 2012 were retrospectively analyzed. The patients were assigned into three groups according to their phosphorus levels as follows: low (blood phosphorus level < 0.8 mmol/L), normal (0.8 ±1.5 mmol/L), and high (>1.5 mmol/L) phosphorus groups.This study was aimed at comparing the clinicopathological features of the three groups and analyzing the influence of blood phosphorus level on patient prognosis.

  Results  Among the 56 patients with CRPC, 13 (23.2%) were in the low phosphorus group; 39 (69.6%) in the normal phosphorus group; and 4 (7.2%) in the high phosphorus group. The median survival time of the three groups were 18, 27, and 24 months, respectively. Significant differences were found among the groups (P < 0.05). A single-factor analysis revealed that the survival time was affected by clinical stage (χ²=3.940, P=0.047), distant metastasis (χ²=5.369, P=0.020), and hypophosphatemia (χ²=6.695, P=0.010). A multivariate analysis of the Cox model revealed that hypophosphatemia, hypercalcemia, and distant metastasis were risk factors related to patient prognosis, with hazard ratios (95% confidence interval) of 5.448 (1.532-19.379), 5.868 (1.897-18.147), and 3.708 (1.300-10.578), respectively.

  Conclusions  The prognosis of the patients with CRPC who had low blood phosphorus levels was poor. Hypophosphatemia, hypercalcemia, and distant metastasis are prognostic risk factors in patients with CRPC. Blood phosphorus level can predict the prognosis of patients with CRPC to a certain extent.