Single-Fraction Stereotactic Body Radiotherapy for Early-Stage Lung Adenocarcinoma Within Atelectasis

Stereotactic body radiotherapy (SBRT) is an established non-invasive treatment for early-stage non-small cell lung cancer (NSCLC) in patients who are medically inoperable or who decline surgery. However, delivering SBRT to tumors within atelectasis presents unique challenges due to anatomical distortion, impaired tumor visualization, and uncertainties in target motion and localization. A 61-year-old woman with severe chronic obstructive pulmonary disease on long-term home oxygen therapy was diagnosed with biopsy-confirmed right upper lobe lung adenocarcinoma located within an area of atelectasis. She was medically inoperable due to critically reduced pulmonary reserve. Staging positron emission tomography-computed tomography (PET-CT) revealed a focal hypermetabolic right upper lobe lesion with no evidence of nodal or distant metastases. The patient received single-fraction SBRT (SF-SBRT) to 34 Gy using a 1 cm isotropic planning target volume margin to account for increased planning and treatment-related uncertainties. Target delineation was guided by PET-CT to distinguish metabolically active tumor from surrounding atelectasis, and image guidance was performed using cone-beam CT matching to surrogate anatomic landmarks due to limited direct tumor visualization. At 6.1 months after SBRT, the patient demonstrated significant metabolic response on PET-CT but developed rapidly progressive brain metastases and died 6.6 months after SBRT. This case demonstrates the feasibility of SF-SBRT for early-stage NSCLC within atelectasis. While short-term metabolic response was achieved, long-term local control remains unclear and further research into the management of lung tumors within atelectasis is warranted.