Dosimetric comparison of free-breathing and deep inspiration breath-hold radiotherapy for lung cancer.

PURPOSE: The goal of this work was to evaluate the potential benefit of deep inspiration breath-hold (DIBH) compared to free breathing (FB) radiotherapy in a homogeneous population of patients with lung cancer. METHODS AND MATERIALS: A total of 25 patients with non-small cell lung cancer treated by DIBH underwent an additional FB CT scan. The DIBH and FB treatment plans were compared. Target volume was compared using coverage, homogeneity, and conformal indices. Organs at risk were compared using V(5), V(13), V(20), V(25), V(37), mean dose (D(mean)) for lungs, V(40) and D(mean) for the heart, V(50), D(mean) and maximum dose (D(max)) for the esophagus, and using biological indices, i.e., the equivalent uniform dose (EUD) and the normal tissue complication probability (NTCP). RESULTS: Median age was 62 years. Prescribed total dose was 66 Gy. Conformity index was improved with DIBH (0.67 vs. 0.58, p = 0.046) but coverage and homogeneity indices were not significantly different. Lung dosimetric parameters were improved using DIBH: D(mean) (13 vs. 15 Gy, p = 10(-4)), V(5) (43 vs. 51%, p = 6.10(-5)), V(13) (31 vs. 38%, p = 2.10(-3)), V(20) (25 vs. 31%, p = 0.01), V(25) (22% vs. 27%, p = 0.01) and V(37) (12 vs. 16%, p = 0.03), EUD (8.2 vs. 9.9 Gy, p = 3.10(-4)), and NTCP (1.9 vs. 4.8%, p = 10(-3)). For the heart, D(mean) (14 vs. 17 Gy, p = 0.003), V(40) (12 vs. 17%, p = 0.004), and EUD (19 vs. 22 Gy, p = 6.10(-4)) were reduced with DIBH, whereas V(30) and NTCP were similar. DIBH improved the D(mean) (28 vs. 30 Gy, p = 0.007) and V(50) (25 vs. 30%, p = 0.003) for the esophagus, while EUD, NTCP, and D(max) were not altered. CONCLUSION: DIBH improves the target conformity index and heart and lung dosimetry in lung cancer patients treated with radiotherapy. The clinical implications of these findings should be confirmed.