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A2476 - Subsolid Nodules in Lung Cancer Screening
Author Block: R. L. Myers1, S. Atkar-Khattra2, J. Mayo3, J. English4, S. Lam1; 1Integrative Oncology, BC Cancer Agency, Vancouver, BC, Canada, 2Integrative Oncology, BC Cancer Research Center, Vancouver, BC, Canada, 3Radiology, Vancouver General Hospital, Vancouver, BC, Canada, 4Pathology, Vancouver General Hosp, Vancouver, BC, Canada.
Rationale Lung cancer screening has the potential to save lives. The National Lung Screening Trail demonstrated a 20% reduction in mortality from lung cancer with low dose CT screening but has been criticized with the over diagnosis of indolent cancers (radiographically classified as non-solid nodules). We describe the follow up of 1004 screen detected subsolid nodules over a 17 year period to determine the malignant potential of these nodules. Methods The participants were part of the Lung Health Study, a lung cancer screening study conducted in Vancouver, Canada that began in 2000. Eligible participants were current or former smokers between the ages of 45 to 74 years of age who smoked for at least 30 years or more. Participants enrolled had a low dose computed tomography (LDCT) of the chest for at least 2 years. Results 1383 participants underwent LDCT scan for early detection of lung cancer. All participants in the study had a minimum of 2 screens, and up to 10 yearly screens. The average follow-up was 7.6 years, ranging from 2 to 17 years. 1004 subsolid nodules were identified on a baseline scan or as a new nodule on a follow up scan and followed over time. They were subclassified into 910 ground glass nodules (GGO) and 94 semi-solid nodules (SSN). Of the 910 GGO, 264 became solid and 1/264 was diagnosed as malignant. 602/910 remained GGO and 11 were found to be malignant. 7/910 became semisolid and 2 were found to be malignant. 3 were PFN, 3 were scars, and 1 a vessel, 262 resolved.
Of the 94 semisolids, 44 stayed semisolid (7 cancer) 1 became a GGO, 2 were scars, 47 became solid (1 cancer) and 33 resolved. 22 nodules (2.4%) were resected and confirmed malignant (14 GGO and 8 SSN in the CT prior to surgery). Nodule follow up ranged from 1 month to 7 years prior to resection. 86% of the malignant nodules resected were greater than 11mm at baseline. All 22 cancers were adenocarcinoma, 20 were stage IA, 1 was IB and 1 was IIIA . Conclusion Although the majority of subsolid nodules picked up on CT screen remain stable or resolve, 2.4% were confirmed malignant. Longer term follow up, beyond the recommended 5 years should be considered as the natural history of these nodules is not entirely known.