Evaluation of Serum Calcium as a Predictor of Biochemical Recurrence following Salvage Radiation Therapy for Prostate Cancer
Table 1
Patient characteristics according to pre-SRT serum calcium level.
Variable
Pre-SRT serum calcium level
P value
Low: ≤9.0 mg/dL
Moderate: >9.0 and ≤9.35 mg/dL
High: >9.35 mg/dL
Pre-RP PSA level (ng/mL)
11.0 (3.4, 32.5)
11.1 (2.6, 56.7)
7.3 (2.0, 44.4)
0.29
Pre-SRT PSA level (ng/mL)
0.7 (0.2, 15.3)
0.6 (0.2, 36.1)
0.8 (0.1, 4.9)
0.12
SRT dose (Gy)
64.8 (60.0, 70.2)
64.8 (58.4, 70.2)
66.6 (54.0, 72.4)
0.16
Age at SRT initiation
67 (48, 80)
68 (55, 79)
68 (44, 85)
0.38
Time from RP to SRT initiation (months)
22 (<1, 117)
20 (2, 126)
24 (3, 181)
0.50
Time from serum calcium measurement to SRT initiation (days)
16 (1, 362)
21 (<1, 361)
21 (<1, 362)
0.73
Pathological tumor stage
0.68
T2
22 (45%)
24 (41%)
28 (49%)
T3a
18 (37%)
20 (34%)
16 (28%)
T3b
9 (18%)
15 (25%)
13 (23%)
Surgical margin
0.66
Positive
27 (57%)
34 (58%)
37 (65%)
Negative
20 (43%)
25 (42%)
20 (35%)
Gleason score
0.49
3–6
17 (38%)
18 (31%)
22 (39%)
7
19 (42%)
26 (45%)
25 (45%)
8–10
9 (20%)
14 (24%)
9 (16%)
Pre-SRT hormone therapy
0.81
Yes
7 (14%)
10 (17%)
11 (19%)
No
42 (86%)
49 (83%)
46 (81%)
Year of start of SRT
0.29
1987–1992
12 (24%)
16 (27%)
14 (25%)
1993–1997
18 (37%)
13 (22%)
12 (21%)
1998–2001
16 (33%)
14 (24%)
10 (18%)
2002–2008
3 (6%)
16 (27%)
21 (37%)
The sample median (minimum and maximum) is given for continuous variables. P values result from Fisher’s exact test or a Kruskal-Wallis rank sum test. Information was not available for the following variables: preoperative PSA (low: 7, moderate: 2, and high: 6), surgical margin (low: 2), and Gleason score (Low: 4, Moderate: 1, High: 1). RP: radical prostatectomy. PSA: prostate specific antigen. SRT: salvage radiation therapy.
