The relationship between the bladder volume and optimal treatment planning in definitive radiotherapy for localized prostate cancer

Figures & data

Table I. Patient characteristics.

	no.
cT stage (TNM 6th ed.)
1–2a	101(42%)
2b	32 (13%)
2c	40 (16%)
3a	61 (25%)
3b	8 (33%)
4	1 (0.4%)
Gleason score
2–6	41 (17%)
7	102 (42%)
8–10	100 (41%)
Pretreatment PSA
0–10	104 (43%)
10–20	67 (28%)
> 20	72 (30%)
D'Amico's risk group
Intermediate	71 (29%)
High	172 (71%)
Neoadjuvant hormone therapy
No	81 (33%)
Yes	162 (67%)
Mean age (range)	70 (42–85)
Mean prostate volume (range)	21 ml (6–178)
Mean PTV (range)	112 ml (61–273)
Mean bladder volume (range)	235 ml (45–653)

cT stage, clinical tumor stage; PSA, prostate-specific antigen; PTV, planning target volume.

Table II. Dose constraints.

Target/Organ		Dose constraint
PTV	D95	100% (76 Gy)
	Maximum	< 110% (83.6 Gy)
	Mean	< 105% (79.8 Gy)
Rectum wall*	V40	< 65%
	V60	< 35%
	V70	< 25%
	V78	< 10%
Bladder wall	V40	< 60%
	V70	< 35%
Sigmoid colon	V65	< 0.5 ml
Small bowel	V60	< 0.5 ml

*Rectum wall within 5 mm above and below the PTV, Vx < y% (or ml) means that no more than y% (or ml) of the volume of the organ receive a dose > x Gy.

PTV, planning target volume.

Table III. Logistic regression analysis between bladder volume and the percentage of patients with an optimal plan.

Bladder volume	Number of patients	Patients with an OP	p	Odds ratio (95% CI)
<100 ml	21	15 (71%)	0.069	0.34 (0.11–1.09)
100–149 ml	34	24 (71%)	0.028	0.33 (0.12–0.89)
150–199 ml	43	37 (86%)	0.761	0.85 (0.29–2.50)
200–249 ml	35	30 (86%)	0.739	0.82 (0.26–2.61)
250–299 ml	27	24 (89%)	0.896	1.10 (0.28–4.31)
>300 ml	83	73 (88%)		1

OP, optimal plan.

Figure 1. The percentage of patients with an OP according to bladder volume. Patients were divided into subgroups according to their bladder volume by 50 ml. The percentage of patients with an OP was defined by dividing the number of patients with an OP by the number of patients in each subgroup. The size of each dot represents the number in each subgroup. n, number of patients; OP, optimal plan.

Table IV. Univariate logistic regression analysis of association with achieving an optimal plan.

	Patients with an OP (n, 203)	Patients without an OP (n, 40)	p
cT stage (TNM 6th ed.)			0.03
1–2a	77 (38%)	24 (60%)
2b	26 (13%)	6 (15%)
2c	35 (17%)	5 (13%)
3a	57 (28%)	4 (10%)
3b	7 (3%)	1 (3%)
4	1 (0.5%)	0 (0%)
Gleason score			NS
2–6	39 (19%)	2 (5%)
7	83 (41%)	19 (48%)
8–10	81 (40%)	19 (48%)
Pretreatment PSA			NS
0–10	85 (42%)	19 (48%)
10–20	58 (28%)	9 (23%)
> 20	60 (30%)	12 (30%)
D'Amico's risk group			NS
Intermediate	60 (30%)	11 (28%)
High	143 (70%)	29 (73%)
Neoadjuvant hormone therapy			0.10
No	63 (31%)	18 (45%)
Yes	140 (69%)	22 (55%)
Mean age (range)	70 (42–85)	73 (59–83)	0.01
Mean prostate volume (range)	21 ml (6–178)	22 ml (12–103)	NS
Mean PTV (range)	109 ml (61–225)	115 ml (77–273)	NS
Mean bladder volume (range)	266 ml (45–594)	214 ml (48–653)	0.04

cT stage, clinical tumor stage; OP, optimal plan; PSA, prostate-specific antigen; PTV, planning target volume.