Positron emission tomography demonstrates radiation-induced changes to nonirradiated lungs in lung cancer patients treated with radiation and chemotherapy.

Study Objectives: To determine whether acute changes in shielded lungs can be detected by positron emission tomography (PET) after radiation therapy.

Design: Retrospective cohort study.

Setting: University-affiliated medical center.

Patients: Sixteen patients undergoing radiation therapy for lung cancer who had PET scans after receiving treatment.

Interventions: None.

Measurements And Results: Thirteen of 16 patients (81.2%) showed increased (18)fluoro-2-deoxyglucose uptake in shielded nonirradiated lung in the following four distinct patterns: (1) contralateral peripheral pleural uptake in 5 of 16 patients (31.2%); (2) ipsilateral peripheral pleural uptake in 5 of 16 patients (31.2%); (3) bilateral peripheral pleural uptake in 1 of 16 patients (6.2%); and (4) bilateral diffuse background uptake in 1 of 16 patients (6.2%). This last patient developed clinically evident radiation pneumonitis.

Conclusions: Increased lung metabolic activity can be demonstrated in the nonirradiated lung in patients who have undergone radiation therapy for lung cancer and can be detected by PET scanning. PET scanning of lungs in irradiated patients may provide an early demonstrable barometer of pulmonary toxicity. If verified, this imaging tool could prove to be useful in monitoring patients receiving radiation therapy for thoracic malignancies and may have predictive value for subsequent fibrosis. PET scanning may also be an important tool in future studies to further elucidate the pathogenetic mechanism of radiation-induced lung injury.