Tumour control probability after Ruthenium-106 brachytherapy for choroidal melanomas

Figures & data

Figure 1. 3D image-guided planning using Plaque Simulator. (A) Recreated tumour position and relative distances to the macula and the optic disc on pre-treatment fundus photography. (B) Retrospectively recreated plaque position based on radiation scar on post-treatment fundus photography. (C) 3D dose distributions were recreated based on the exact treatment time extracted for each patient. The 200 Gy, 100 Gy, and 20 Gy isodose lines are shown. (D) 3D illustration of the recreated treatment plan showing plaque position, the tumour, macula, and optic disc. An anterior view was chosen for illustration purposes.

Table 1. Patient-, tumour-, and treatment characteristics.

	Value (median (range, IQR))
Patient characteristics
Age (years)	62 (23–94, 53–69)
Male/female (n)	118/108
Left/right eye (n)	117/109
Tumour characteristics
Largest base dimension (mm)	11.4 (4.4–23.0, 9.0–13.4)
Height (mm)^a	3.9 (1.3–12.0, 2.8–5.8)
T category 1/2/3/4 (n)	78/100/39/9
AJCC stage I/II/III (n)	73/137/16
Macula-tumour distance (mm)	2.5 (0.0–15.7, 0.3–5.0)
Optic disc-tumour distance (mm)	2.4 (0.0–14.7, 0.4–4.9)
Treatment characteristics
Treatment time (hours)	120 (26.2–912.2, 74–191)
Plaque type CCA/CCB/CCC/COB	53/101/12/60
Combined TTT and Ru-106 brachytherapy (n)	29
TTT during follow-up (n)	19
D99% (Gy)	105 (5.7–783.3, 65–138)
D98% (Gy)	112 (6.8–837.8, 70–145)
BED99% (Gy)	551 (7.9–6514.8, 213–977)
Recurrence characteristics (n = 50)
Recurrence site (apex/base/new location)	31/17/2
Plaque type CCA/CCB/CCC/COB	3/21/3/23
T category 1/2/3/4 (n)	12/23/11/4
AJCC stage I/II/III (n)	12/34/4
Optic disc-tumour distance (mm)	1.6 (0.0–13.8, 0.0–3.3)
D99% (Gy)	69 (5.7–168.9, 44–97)

IQR: interquartile range; T: tumour; AJCC: American Joint Committee on Cancer; TTT: transpupillary thermotherapy; Ru-106: Ruthenium-106; D_99%: dose to 99% of the tumour volume (minimum physical tumour dose); D_98%: dose to 98% of the tumour volume (near-minimum physical tumour dose); BED_99%: biologically effective dose to 99% of the tumour volume (minimum BED tumour dose).

^a Tumours with height > 5 mm: n = 73.

Figure 2. (A) A Kaplan-Meier curve for local control for the entire patient population. Dotted lines: 95% confidence intervals; crosses: censored patients. (B) Tumour control probability (TCP) at 3 years with 95% confidence interval using D_99%. The TCP curve adjusted for tumour height of 3.9 mm (median height of cohort), no combined TTT and Ru-106 treatment (most common in the cohort), and male sex (most frequent in the cohort). (C) TCP curve at 3 years using BED_99%. The TCP curve used no combined TTT and Ru-106 treatment (most common in the cohort) and male sex (most frequent in the cohort). Both TCP curves (B and C) were based on Cox proportional hazard regression, and the data points represent Kaplan-Meier estimates at 3 years after stratifying into four dose groups (for illustration purpose only).

Table 2. Cox proportional hazards.

	HR (95% CI)	p-Value
Variables in full model
Age	1.03 (1.00–1.05)	.04
Sex (male relative to female)	2.02 (1.11–3.70)	.02
Eye (left relative to right)	1.00 (0.58–1.73)	.9
Tumour height	1.21 (1.07–1.38)	.002
Optic disc-tumour distance	0.96 (0.86–1.08)	.51
D99%	0.89 (0.83–0.95)	.0007
Combined TTT and Ru-106 brachytherapy	1.80 (0.91–3.56)	.09
Variables in reduced model
D99%	0.87 (0.82–0.93)	<10^–4
Tumour height	1.22 (1.09–1.37)	.0007
Combined TTT and Ru-106 brachytherapy	2.14 (1.11–4.13)	.02
Sex (male relative to female)	1.85 (1.02–3.33)	.04

HR: hazard ratio; CI: confidence interval; D_99%: minimum physical tumour dose; TTT: transpupillary thermotherapy; Ru-106: Ruthenium-106. Tumour heights and optic disc-tumour distances are continuous variables measured in mm. HRs for a 10 Gy increase in D_99%.

Figure 3. Tumour control probability (TCP) curves taking dose and tumour height into account (tumour heights based on mean values of each tumour staging group). (A) TCP for D_99% at 3 years. (B) TCP for D_99% at 7 years. TCP curves were based on Cox proportional hazard regression, using no combined TTT and Ru-106 treatment (most common in the cohort) and male sex (the most frequent sex in the cohort).