Table 3.
Multivariable analysis association between pre-SRT serum calcium and BCR of prostate cancer after SRT.
| Model adjustment | Association of pre-SRT serum calcium and BCR of prostate cancer after SRT | |||||
|---|---|---|---|---|---|---|
|
Pre-SRT serum calcium as a continuous variable (0.5 mg/dL increase) |
Moderate versus low pre-SRT serum calcium |
High versus low pre-SRT serum calcium |
||||
| RR (95% CI) | P value | RR (95% CI) | P value | RR (95% CI) | P value | |
| No adjustment for other variables | 0.96 (0.74, 1.25) | 0.76 | 0.94 (0.59, 1.50) | 0.79 | 1.08 (0.66, 1.75) | 0.76 |
| Adjusting individually for risk factors for BCR | ||||||
| Pathologic tumor stage | 0.99 (0.75, 1.30) | 0.91 | 0.89 (0.55, 1.42) | 0.61 | 1.12 (0.69, 1.82) | 0.65 |
| Gleason score | 0.94 (0.74, 1.25) | 0.68 | 0.96 (0.59, 1.56) | 0.86 | 1.15 (0.69, 1.92) | 0.59 |
| Pre-SRT PSA | 0.95 (0.73, 1.24) | 0.70 | 0.93 (0.58, 1.49) | 0.76 | 1.10 (0.68, 1.78) | 0.71 |
| SRT dose | 0.98 (0.74, 1.28) | 0.86 | 0.91 (0.57, 1.45) | 0.68 | 1.10 (0.68, 1.79) | 0.70 |
| Adjusting for all four risk factors for BCR | 0.95 (0.71, 1.28) | 0.75 | 0.91 (0.55, 1.48) | 0.69 | 1.21 (0.72, 2.04) | 0.47 |
| Adjusting for all four risk factors for BCR and: | ||||||
| Preoperative PSA | 0.93 (0.67, 1.28) | 0.65 | 0.88 (0.53, 1.47) | 0.63 | 1.11 (0.64, 1.94) | 0.72 |
| Age at SRT initiation | 0.98 (0.72, 1.32) | 0.87 | 0.93 (0.57, 1.52) | 0.76 | 1.26 (0.74, 2.13) | 0.39 |
| Time from RP to SRT initiation | 0.96 (0.71, 1.29) | 0.76 | 0.90 (0.55, 1.48) | 0.69 | 1.24 (0.73, 2.09) | 0.43 |
| Time from serum calcium measurement to SRT initiation |
0.95 (0.70, 1.28) | 0.74 | 0.89 (0.54, 1.45) | 0.64 | 1.21 (0.72, 2.03) | 0.48 |
| Surgical margin | 0.93 (0.69, 1.26) | 0.63 | 0.88 (0.54, 1.44) | 0.61 | 1.16 (0.69, 1.96) | 0.57 |
| Pre-SRT hormone therapy | 0.94 (0.70, 1.26) | 0.66 | 0.86 (0.53, 1.40) | 0.55 | 1.20 (0.72, 2.02) | 0.48 |
| Year of start of SRT | 0.95 (0.70, 1.28) | 0.73 | 0.90 (0.55, 1.47) | 0.67 | 1.19 (0.70, 2.01) | 0.51 |
Relative risks, 95% confidence intervals, and P values result from the Cox proportional hazards regression models. Low pre-SRT serum calcium was considered to be ≤9.0 mg/dL. Moderate pre-SRT serum calcium was considered to be >9.0 mg/dL and ≤9.35 mg/dL. High pre-SRT serum calcium was considered to be >9.35 mg/dL. BCR: biochemical recurrence. RR: relative risk. CI: confidence interval. SRT: salvage radiation therapy. RP: radical prostatectomy.