Image-Guided Hypofractionated Radiation Therapy with Stereotactic Boost for Inoperable Stage III Non-Small Cell Lung Cancer

Purpose/objective(s): To evaluate the dosimetric feasibility of a hypofractionated radiotherapy schedule for Stage III non-small cell lung cancers (NSCLC). Materials/Methods: The study sample included 14 cases. The mean tumor burden (primary and nodal areas) was 111 cm3, range 10-424 cm3. Intended plans consist of an initial dose of 40 Gy in 10 fractions, followed by a 7 Gy x 5 boost. The clinical target volumes (CTV) consisted of PET avid areas only; the initial dose was delivered to the CTV+5 mm margin, and the boost to the CTV (no margin). At an alpha/beta ratio of 10, the tumor dose equivalent at 2 Gy per fraction of the proposed regimen is 94 Gy. Results: Overall, only one of the 14 plans was considered unacceptable (lung and heart constraints were significantly exceeded). The spinal cord maximum constraint was met in all cases. The average spinal cord maximal dose from the actual plans was 31 Gy, range 21-38 Gy (2-Gy equivalent=32 Gy, range 18-43). The esophageal mean constraint was met in all cases; average dose 13 Gy (range 6-22). The mean heart dose was 7 Gy (range 1-33). The mean % volume of total lung-PTV receiving 15 Gy was 27% (range 17-50%). The total lung-PTV mean dose was 11 Gy (range 6-17). The tracheobronchial tree constraint (V50 Gy) was set at 15 cm3 and was met in 11 of the 14 cases; three cases marginally exceeded the limit. The brachial plexus was relevant for three patients, with an average V45 Gy of 0.6 cm3 (range 0-8.) Conclusions: This study demonstrates the dosimetric feasibility of an aggressive hypofractionated regimen for Stage III lung cancer patients. Categories: Radiation Oncology