Predictive parameters in hypofractionated whole-breast 3D conformal radiotherapy according to the Ontario Canadian trial

Figures & data

Table 1 Characteristics of patients and clinical parameters

Patients	215
Mean age (years)	68 (60–75)
Stage pT1 pN0/pT2 pN0	55/160
Chemotherapy/hormonal	80/135
Antracycline-containing scheme	44
Cyclophosfamide-methotrexate-5-fluorouracil	36
Good surgery score	170
Fair surgery score	45
Mean breast volume	1,250 cc (560–1,500)
Breast separation diameter <25 cm	135
Breast separation diameter >25 cm	80

Table 2 Results of late toxicity and cosmesis at mean 6-year follow-up

Toxicity G1/G2	47 patients (22%)
Toxicity G3 (skin and subcutaneous)	11 patients (5%)
Cosmesis (excellent/good)	172 patients (80%)
Cosmesis (fair/poor)	43 patients (20%)

Abbreviation: G, grade.

Figure 1 The NTCP model for late tissue predicts the double-trouble (according to higher fraction size) and triple-trouble (according to high total dose) effects for hotspots >10% of PD (blue dotted line) and for hotspots >20% of PD (pink dotted line). *The formula refers to Lyman’s model¹⁸ but the original data from this study has been applied.

Abbreviations: NTCP, normal tissue complication probability; PD, prescribed dose; PTV, planning target volume; BED, biologically effective dose.

Table 3 Univariate analysis (χ²) for relation of late toxicity and cosmesis

Parameters	Tox G1/G2	Tox G3	Cosmesis (Exc/good)	Cosmesis (F/P)
PTV <1,300 cc	P=0.2	P=0.3	P=0.03	P=0.3
PTV >1,300 cc	P=0.16	P=0.003	P=0.2	P=0.005
V110 <10%	P=0.6	P=0.5	P=0.004	P=0.5
V110 >10%	P=0.5	P<0.005	P=0.1	P=0.005

Abbreviations: Exc, excellent cosmesis; F, fair cosmesis; G, grade; P, poor cosmesis; PTV, planning target volume; Tox, late toxicity; V110, volume of the PTV breast taking 110% of the prescribed dose.

Table 4 Univariate analysis (paired t-test)

Parameters	Correlation	P-value
V110 and toxicity	0.403	<0.001
PTV and toxicity	0.955	<0.001
CT and toxicity	−0.085	0.021
BD and toxicity	0.110	0.11
Surgery and toxicity	0.455	<0.001
Cosmesis and PTV	0.485	<0.001
Cosmesis and V110	0.938	<0.001
Cosmesis and CT	0.022	0.750
Cosmesis and BD	0.285	<0.001
Cosmesis and surgery	0.938	<0.001

Notes: Toxicity G1/G2 =0 and G3 =1; cosmesis good =0 and fair =1; PTV <1,300 cc =0 and PTV >1,300 cc =1; V110 <10% =0 and V110 >10% =1; BD <25 cm =0 and BD >25 cm =1; surgery good =0 and poor =1; CT =1 and no CT =0.

Abbreviations: cosmesis, excellent/good/fair/poor; CT, chemotherapy; BD, breast diameter as the breast width exceeding 25 cm at the posterior border of the medial and lateral tangential beams; G, grade; PTV, planning target volume; surgery, good or poor by Taylor; V110, volume of the PTV breast taking 110% of the prescribed dose.

Figure 2 Forest plot for multivariate analysis.

Notes: Correlation between variables and toxicity: diamonds over the green line represent as strong correlation; diamond before the yellow line represents as weak correlation; and diamond on the red line represents no correlation.
Abbreviations: PTV, planning target volume; G, grade; V110, volume of the PTV breast taking 110% of the prescribed dose; CT, chemotherapy.

Table 5 Pearson’s covariance for multivariate analysis

	Toxicity	PTV	V110	BD	Cosmesis	Surgery	CT
PTV
R	0.955**	1	0.430**	0.127	0.485**	0.485**	−0.073
P	<0.001	–	0.00	0.067	<0.01	0.000	0.289
V110
R	0.403**	0.430**	1	0.285**	0.938**	0.969**	0.022
P	<0.001	0.000	–	0.000	<0.01	0.000	0.750
BD
R	0.110	0.127	0.285**	1	0.285**	0.256**	−0.019
P	0.111	0.067	0.000	–	<0.01	0.000	0.788
Surgery
R	0.455**	0.485**	0.969**	0.256**	0.938**	1	0.048
P	<0.001	0.000	0.000	0.000	<0.01	–	0.490
CT
R	−0.085	−0.073	0.022	−0.019	0.022	0.048	1
P	0.221	0.289	0.750	0.788	0.750	0.490	–

Notes: Toxicity G1/G2 =0 and G3 =1; cosmesis good =0 and fair =1; PTV <1,300 cc =0 and PTV >1,300 cc =1; V110 <10% =0 and V110 >10% =1; BD <25 cm =0 BD >25 cm =1; surgery good =0 and poor =1; CT =1 and no CT =0).

** A very high value of Pearson’s correlation number confirmed in the double tail test.

Abbreviations: BD, breast diameter as the breast width exceeding 25 cm at the posterior border of the medial and lateral tangential beams; cosmesis, excellent/good/fair/poor; CT, chemotherapy; G, grade; PTV, planning target volume; surgery, good or poor by Taylor; V110, volume of the PTV breast taking 110% of the prescribed dose; P, statistical significance; R, correlation number.

LymanJTComplication probability as assessed from dose-volume histogramsRadiat Res Suppl19858S13S193867079

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