Abstract 3250: Survival of patients with incident lung cancer following screening by computed tomography in the National Lung Screening Trial
Authors: Schabath Matthew B. , Massion Pierre P. , Thompson Zachary J. , Balagurunathan Yoganand , Goldof Dmitry , Eschrich Steven A. , Gillies Robert J. 
Published: May 2015

Abstract
Background: The National Lung Screening Trial (NLST), which compared low-dose helical computed tomography (CT) and standard chest radiography (CXR), found a 20% relative risk reduction in lung cancer mortality for annual screening over 3 years for CT versus CXR. We performed a post hoc analysis comparing patient characteristics and survival of incident lung cancer patients in the CT arm of the NLST.
Methods: We identified four distinct incident lung cancer case cohorts in the CT arm of the NLST. Two of the case cohorts (CC) developed lung cancer following one (CC1) or two (CC2) prior CT detections of non-cancer (or indeterminate) nodules. CC1 patients (N=104) had a non-cancer nodule at T0 (baseline) then developed lung cancer at T1 (1st follow-up); CC2 patients (N=92) had a non-cancer nodule at T0 and T1 then developed lung cancer at T2. The other two case cohorts developed lung cancer following one (CC3) or two (CC4) negative CT screens (i.e., no evidence of nodules). CC3 patients (N=62) had a negative screen at T0 then developed lung cancer at T1; CC4 patients (N=63) had negative screens at T0 and T1 then developed lung cancer at T2. Analyses were performed to assess overall survival (OS) and progression-free survival (PFS).
Results: CC1 and CC2 had significantly better OS and PFS compared to CC3 and CC4 and the 5-year survival rates were significantly higher for CC1 (65.9%) and CC2 (67.5%) versus CC3 (41.0%) and CC4 (55.2%). There were no significant differences in risk factors across the four case cohorts; however, there were fewer stage I patients in CC3 (53.3%) compared to CC1, CC2, and CC4 (68.3%, 66.3%, and 65.1%, respectively) and the percentage of patients who died from lung cancer was significantly higher for CC3 (50%) compared to CC1, CC2, and CC4 (27.9%, 26.1%, 36.5%, respectively). CC1 and CC2 compared to CC3 and CC4 had a significantly higher percentage of adenocarcinoma (42.3% and 34.8% vs. 24.2% and 26.9%) and lower percentages of small cell carcinoma (3.9% and 9.8% vs. 17.7% and 9.5%) and squamous cell carcinoma (17.3% and 16.3% vs. 25.8% and 38.1%). The differences in survival were consistent for adenocarcinoma and squamous cell tumors. When compared to CC1/CC2 combined (HR=1.0), multivariable Cox proportional models revealed that CC3 alone (HR=1.71; 95% CI 1.06-2.76) and CC3/CC4 combined (HR=1.63; 95% CI 1.08-2.45) were associated with a significantly increased risk of death after adjusting for age, gender, race, smoking, family history of lung cancer, COPD, stage, histology, and treatment.
Conclusions: Patients diagnosed with lung cancer who had at least one CT screen revealing a non-cancer nodule prior to cancer diagnosis had significantly better survival compared to patients who had at least one negative screen prior to cancer diagnosis. These analyses suggest that patients diagnosed with lung cancer that had a negative screen prior to their cancer diagnosis developed tumors with more aggressive biology.
Citation Format: Matthew B. Schabath, Pierre P. Massion, Zachary J. Thompson, Yoganand Balagurunathan, Dmitry Goldof, Steven A. Eschrich, Robert J. Gillies. Survival of patients with incident lung cancer following screening by computed tomography in the National Lung Screening Trial. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3250. doi:10.1158/1538-7445.AM2014-3250