Pulmonary function tests – an easy selection method for respiratory-gated radiotherapy in patients with left-sided breast cancer

Figures & data

Table I. Patient characteristics for the two groups, group I (n = 16) and group II (n = 18). Mean ± SD and range (in brackets) are shown.

	Group I	Group II	p-Value
Laterality	Left	Left	N.A.
BCS^1	16	16	N.A.
Mastectomy	0	2	N.A.
Age (years)	56.7 ± 9.5 [29.0–70.0]	55.6 ± 8.4 [44.0–70.0]	0.50
TLV-CT FB^2 (dm^3)	2.5 ± 0.6 [1.5–3.3]	2.5 ± 0.5 [2.1–3.6]	0.83
CTV1^3 (cm^3)	615.8 ± 264.7 [315.5–1193.0]	619.2 ± 300.9 [226.1–1500.4]	0.97
Heart volume (cm^3)	608.0 ± 69.3 [460.7–725.1]	628.3 ± 106.8 [449.7–812.2]	0.51

¹Breast conservative surgery (BCS); ²The total lunge volume (TLV-CT) was automatically delineated in CT-series recorded during free breathing (FB); ³CTV1 includes left mammary gland only, and was delineated for patients with breast conservative surgery (group I: 16 of 16 patients, group II: 16 of 18 patients).

Figure 1. Relative heart volume receiving 25 Gy or more (V25Gy) and mean heart dose (D_mean) for PTV1 (A and C) and PTV2 (B and D) plotted against total lung volume (TLV-CT), measured in CT series acquired during FB for patients in group I (n = 16). Presented is the estimated regression line (solid line) with 95% confidence interval (dotted lines) and Pearson's correlation coefficient, r. The dotted line in A and B represent V25Gy = 5%, and the dotted line in C and D represent D_mean = 2 Gy.

Figure 2. ROC curves for patients from group I (n = 16) with PTV1 (A) and PTV2 (B) as target volume, in a setting where the total lung volume (TLV-CT) during free breathing (FB) was selected as predictor for getting a heart dose higher than recommended in the national guidelines (V25Gy > 5%) at the time when the study was conducted. The TLV-CT cut-off values with the highest summarized value of sensitivity and specificity were determined to be 2.2 and 2.7 dm³ for patients with PTV1 and PTV2, respectively.

Figure 3. Scatterplots of TLV-CT versus TLV-PFT_{1 + 2} (A) and TLV-PFT₃ (B), respectively. Presented is the estimated regression line (solid line) with 95% confidence interval (dotted lines). The estimated R² is 0.717(p < 0.01) and 0.753 (p < 0.01) for the plot in Figures A and B, respectively. Corresponding Bland-Altman plots are shown in the lower part of the figure.