Extrapulmonary soft-tissue fibrosis resulting from hypofractionated stereotactic body radiotherapy for pulmonary...

To clarify the incidence, symptoms, and timing of extrapulmonary fibrosis developing after hypofractionated stereotactic body radiotherapy.

We analyzed 379 consecutive patients who underwent stereotactic body radiotherapy for lung tumors at four institutions between February 2001 and March 2007. The median follow-up time was 29 months (range, 1-72). We investigated the subjective and objective characteristics of the extrapulmonary masses, redelineated the origin tissue of each on the treatment planning computed tomography scan, and generated dose-volume histograms.

In 9 patients (2.4%), extrapulmonary masses were found 3-36 months (median, 14) after irradiation. Coexisting swelling occurred in 3 patients, chest pain in 2, thumb numbness in 1, and arm edema in 1 patient. Extrapulmonary masses occurred in 5 (5.4%) of 92 and 4 (1.4%) of 287 patients irradiated with a 62.5-Gy and 48.0-Gy isocenter dose, respectively. The mean and maximal dose to the origin tissue was 25.8-53.9 Gy (median, 43.7) and 47.5-62.5 Gy (median, 50.2), respectively. In 5 of 9 patients, the standardized uptake values on 18F-fluorodeoxyglucose-positron emission tomography was 1.8-2.8 (median, 2.2). Percutaneous needle biopsy was performed in 3 patients, and all the specimens showed benign fibrotic changes without malignant cells.

All patients should be carefully followed after stereotactic body radiotherapy. The findings of any new lesion should prompt an assessment for radiation-induced extrapulmonary fibrosis before an immediate diagnosis of recurrence is made. Careful beam-shape modification and dose prescription near the thoracic outlet are required to prevent forearm neuropathy and lymphedema.