Multifocal adenocarcinoma of the lung: Factors predictive for local therapy.

Abstract

e20041 Background: Multifocal Adenocarinoma (MAC) of the lung is a clinical entity of multiple synchronous or metachronous, often ground-glass opacities (GGO) on CT scan, typically indolent-behaving cancers. There is a paucity of clinical data to guide treatment decisions. MACs are often monitored via serial imaging with local therapy (radiation, surgery) employed at the discretion of the clinician. We sought to examine factors predictive of local therapy (Tx) at our institution, to develop standardized objective radiolographic parameters to guide treatment. Methods: We retrospectively reviewed pts seen in the MGH Thoracic Oncology Clinic from 2009-15. 39 pts with MAC were identified and serial CT scans were reviewed, assessing up to 5 nodules per pt. We excluded pts presumed to have MAC by imaging but without confirmatory pathology, those with calcified nodules and < 3 yrs of imaging. Demographics and clinical information were collected and univariant and multivariable logistic regression models were fit to assess correlation with Tx. Results: Among the 39 pts, 84% were female and 92% were smokers (18% active, 51% former > 10pkyr, 23% former < 10pkyr). 149 nodules were identified with median size 11mm (range 5-55mm); the majority of pts had ≥3 nodules (36/39). 66 (44%) nodules received Tx (10 RT, 56 surgery). Radiographic variables significantly associated with Tx were baseline nodule size (p = 0.02) and solid density (p < 0.001). Nodules > 2.5cm at baseline had Tx 77% of the time, while those ≤ 0.7cm had Tx 41%. Median length of monitoring before Tx was 2.1yrs for solid nodules, 3.5yrs for subsolid nodules, and > 11yrs for pure GGOs. Other observations included discordant genotypes between nodules within 1 pt and an overall pattern of nodule contraction just prior to growth acceleration. Conclusions: Lung MAC cases can be successfully managed with serial observation and intervention on growing solid or subsolid nodules. Those with GGO components can often be surveilled for yrs, or if pure GGO, for a decade or more. Larger size at baseline and solid density significantly correlate with the use of Tx. Examples of nodule contraction with concurrent enlargement of the solid component will be presented at ASCO, as this may be an important clinical warning sign.