Multiple Primary Lung Cancers: Treatment Outcomes After Stereotactic Body Radiotherapy (SBRT)

Patients with lung cancer sometimes present with multiple primary lung cancers (MPLCs), either simultaneously (synchronous) or after treatment of an initial lesion (metachronous). Although open surgery remains a treatment mainstay for patients with stage I-II non-small-cell lung cancer (NSCLC), stereotactic body radiation therapy (SBRT) is an acceptable alternative for patients who are medically unfit for or who refuse surgery. In this study, we retrospectively examine the outcome among patients with early-stage MPLCs treated at our institution with SBRT.

Patients at our institution receiving SBRT for MPLC between June 2011 and March 2020 were reviewed retrospectively. Prior to undergoing definitive SBRT, the imaging, and pathology for every patient were reviewed in a multi-disciplinary thoracic/pulmonary tumor board. Dose and fractionation varied with the most common prescriptions being 50 Gy/5 fractions, 56 Gy/4 fractions, and 55 Gy/5 fractions.

A total of 38 patients with a total of 80 MPLCs were treated, among which 68 were T1 lesions and 12 were T2 lesions. Median follow-up was 25.9 months, with local control (LC) rates calculated per lesion to be 98.6%, 93.3%, and 88.2% at one, two, and three years. Median overall survival (OS) was 43.5 months; 83.6%, 67.8%, and 52.3% at one, two, and three years, respectively. Sixty-two of the 80 (77.5%) treated lesions were not associated with any subsequent acute or late toxicity. The 18 (22.5%) lesions associated with toxicity included nine acute and nine late events. All toxicity was either grade 1 (13 of 18) or grade 2 (five of 18).

SBRT for early-stage MPLC achieves high control rates with limited toxicity. MPLC patients deemed unfit for open surgical management should be considered for definitive SBRT.