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We hypothesize that the incidence of screen-detected lung cancer (LC), in participants with previously negative scans, will be highest in the cohort with the highest baseline risk score.Individuals with negative baseline screening results from the Princess Margaret International Early Lung Cancer Action Program before 2009 underwent low-dose computed tomography rescreening from 2015 to 2018. Individuals were contacted in order of descending risk, as determined by the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial's PLCOOf the 1261 participants we attempted to re-contact, 359 participants returned for a rescreening scan (mean of 7.6 years between scans). Participants were divided into low (2%), moderate (≥2% to3.5%), and high baseline risk (≥3.5%) cohorts. On average, those in the high-risk cohort compared to the moderate- and low-risk cohorts were older (66 years versus 62 and 59 years) and had a greater smoking history (54 pack-years versus 47 and 29 pack-years). The incidence of cancer in the high-risk cohort was significantly higher than in the moderate-risk cohort (11% versus 1.7%, p = 0.002).There was a significantly higher incidence of LC in the high-risk cohort than in the moderate-risk cohort. The cut-point between the high- and moderate-risk was determined to be greater than or equal to 3.5% of the 6-year baseline risk.

Purpose To assess the incidence of lung cancer in a cohort of patients with negative findings at previous lung cancer screening. Materials and Methods In this prospective cohort study, the authors first identified 4782 individuals who had negative screening results as part of the International Early Lung Cancer Action Program (1993-2005). Subjects were assigned a lung cancer risk score by using a validated risk model. Starting with those at highest risk, subjects were interviewed by phone and invited to undergo low-dose CT between March 2013 and October 2016. Subjects with a diagnosis of lung cancer and those who had died of lung cancer were determined. Descriptive statistics were used to summarize data. The independent samples t test and Fisher exact test were used to compare age, sex, and risk scores. Results A total of 327 study participants were contacted, and 200 subjects participated in this study. The average age was 74 years (range, 57-88 years), and the median time since previous CT was 7 years. The incidence rate of developing lung cancer during the next 6 years was estimated at 5.6%. The period prevalence of lung cancer was 20.8% (new and preexisting lung cancer, 68 of total cohort of 327). The detection rate of low-dose CT was 7% (14 of 200 subjects). Of the 14 screening-detected cancers, 12 were stage I or II. Conclusion High-risk individuals have a high incidence of lung cancer after previous negative lung cancer screening. Early-stage lung cancer can be successfully detected in older high-risk individuals. © RSNA, 2018 Online supplemental material is available for this article.

282 Background: Coordinating lung cancer screening requires risk assessment for patient selection. Optimal selection can reduce costs and improve efficiency of low dose computed tomography (LDCT) screening of lung cancer. This study evaluated clinic-based spirometry as a tool to improve patient selection for lung cancer screening. Methods: Eligibility criteria for three large LDCT screening studies were retrospectively applied to the highest risk patients enrolled in the Princess Margaret Lung Cancer Screening Program who had received clinic-based research spirometry. The three studies were: Danish Lung Cancer Screening Trial (DLST), National Lung Screening Trial (NLST), and the Ontario Lung Cancer Screening Program (OLCS). Lung cancer incidence was compared between those who would were included by the screening study eligibility criteria (Group I), those who were excluded by the eligibility criteria but demonstrated obstruction on spirometry (defined as a Forced Expiratory Volume in 1 Second % Predicted (FEV1%) < 90%) (Group II), and those who did not meet eligibility criteria and had no obstruction (FEV1% ≥90) (Group III). Results: The 321 highest risk participants of the screening program had a mean age of 65 years and were 39% male. The median number of pack years in this group was 39. After undergoing spirometry, this cohort was screened using LDCT for a median of 3.3 years (range 1–8.1 years). Under DLST criteria, Groups I and II had virtually identical lung cancer incidences detected by screening at 13.1% and 13.6% of the individuals screened, respectively; Group III had a substantially lower incidence at 6.3%. Results were similar by NLST criteria where the incidence of screen-detected lung cancer were 13.7% for Groups I, 11.1% for Group II, and 8.6% for Group III. Under OLCS criteria, these values were 13.4% (Group I), 13.5% (Group II), and 8.2% (Group III). Conclusions: Individuals who were excluded from LDCT screening because they lacked other clinical eligibility criteria, but had a FEV1 < 90%, had similar lung cancer incidence as patients who had met screening study eligibility criteria. Coordinating care for screening of at-risk individuals could be improved by incorporating spirometric tools.

The graphical analysis of the income and substitution effects is an important part of consumer theory that is commonly taught at the level of intermediate microeconomics. Few textbooks, however, devote much discussion of these effects for perfect substitutes. The purpose of this paper is to fill that gap by producing a more complete graphical analysis of the subject matter and thereby enhance student learning.

Objective The Department of Medical Imaging at the University Health Network in Toronto is performing a lung cancer screening study, utilizing low-dose computed tomography (LDCT) as the modality. Baseline and annual repeat results are reported on the first 3352 participants, enrolled between June 2003 and May 2007. Methods Enrollment was limited to those aged 50 years or older, with a smoking history of at least 10 pack-years, no previous cancer and general good health. A helical low-dose CT (LDCT) of the chest was performed using 120 kVp, 40–60 mA, images were reconstructed with 1–1.25 mm overlapping slices. The primary objectives were the detection of parenchymal nodules and diagnosis of early stage lung cancer. Baseline LDCTs were termed positive if at least one indeterminate non-calcified nodule 5 mm or larger in size, or non-solid nodule 8 mm or larger in size was identified. Follow up periods for individuals with a positive baseline LDCT were determined by nodule characteristics. Results The median age at baseline was 60 years (range 50–83), with a median of 30 pack-years of cigarette smoking (range 10–189). Baseline CT evaluations were positive in 600 (18%) participants. To date, 2686 (80%) of the participants have returned for at least one annual repeat screening LDCT. Biopsies have been recommended for 82 participants since the study began, and 64 have been diagnosed with screen-detected cancer (62 lung, two plasmacytoma of the rib). A total of 65 lung cancers have been diagnosed (62 screen-detected, 3 interim), 57 are NSCLC (82% with known stage are stage I or II) and the rate of surgical resection was 80%. Sensitivity and specificity of the protocol in successfully diagnosing early stage lung cancers were 87.7% and 99.3%, respectively. Conclusions Data indicate that LDCT can identify small lung cancers in an at-risk population. The diagnostic algorithm results in few false-positive invasive procedures. Most cancers are detected at an early stage, where the cancer is resectable with a greater potential for cure. Long-term follow up of lung cancer cases will be carried out to determine survival.