Table 2: Single variable analysis association between pre-SRT serum calcium and BCR of prostate cancer after SRT.

Serum calciumCumulative incidence of BCR (95% CI)P value
3 years after SRT5 years after SRTRR (95% CI)

Continuous variable (per 0.5 mg/dL increase)N/AN/A0.96 (0.74, 1.25)0.76
Categorical variable
 Low: 9.0 mg/dL41% (26%–54%)55% (38%–67%)1.00 (reference)N/A
 Moderate: >9.0 and ≤9.35 mg/dL40% (26%–52%)52% (37%–64%)0.94 (0.59, 1.50)0.79
 High: >9.35 mg/dL44% (29%–56%)49% (33%–62%)1.08 (0.66, 1.75)0.76

Relative risks, 95% confidence intervals, and P values result from single variable the Cox proportional hazards regression models. BCR: biochemical recurrence. RR: relative risk. CI: confidence interval. SRT: salvage radiation therapy. N/A: not applicable.