Outcomes of Long-term Interval Rescreening With Low-Dose Computed Tomography for Lung Cancer in Different Risk Cohorts.

INTRODUCTION: 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. METHODS: 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 PLCOM2012 6-year LC risk-prediction model, and then categorized into three risk cohorts according to their baseline risks. The incidence of LC in each risk cohort was determined and compared. Chi-square testing was used for categorical variables and one-way analysis of variance on ranks was used for continuous variables. RESULTS: Of 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% to <3.5%), 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). CONCLUSIONS: 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.

Importance of Long-term Low-Dose CT Follow-up after Negative Findings at Previous Lung Cancer Screening.

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.

Lung cancer screening using low-dose computed tomography in at-risk individuals: the Toronto experience.

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 120kVp, 40-60mA, images were reconstructed with 1-1.25mm 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 5mm or larger in size, or non-solid nodule 8mm 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.

Lung cancer screening with low-dose computed tomography: Canadian experience.

INTRODUCTION: In 2003, the Department of Medical Imaging at the University Health Network in Toronto, Ontario, became the first Canadian site of the Intemational Early Lung Cancer Action Program (I-ELCAP). We report the results from the first 1000 baseline studies. METHODS: Between June 2003 and December 2005, we enrolled 1000 high-risk smokers (that is, smokers with a history of at least 10 pack years, or the equivalent of one pack daily for 10 years), aged 55 years or older. A low-dose helical computed tomography (CT) (40 to 60 mA, 120 kV) was performed with 1.0 mm to 1.25 mm collimation. Nodules found at baseline were followed according to the I-ELCAP protocol: (1) no noncalcified nodules (NCNs) or NCNs < or =4 mm or nonsolid nodules < 8 mm, annual repeat; (2) NCNs > or =5 mm or nonsolid nodules > or =8 mm, 3-month follow-up; or (3) nonsolid nodules > or =15 mm, antibiotics and 1-month follow-up. RESULTS: The first 1000 study participants were aged 63 years, standard deviation (SD) 6 years, with a smoking history of 38 pack years, SD 22 pack years; 662 (66%) were former smokers, and 338 (34%) were current smokers; 453 (45%) were men, and 547 (55%) were women. Of the participants, 256 (26%) had a positive baseline low-dose computed tomography (LDCT) scan; 227 (23%) were followed after 3 months and 16 (1.6%) after 1 month; 7 (0.7%) received a contrast-enhanced CT and 6 (0.6%) an immediate CT-guided biopsy. Twenty-six invasive procedures were performed: 22 CT-guided biopsies, 1 ultrasound-guided lymph node metastasis biopsy, 1 bronchoscopic biopsy, and 2 surgeries. The malignancy rate of the invasive procedures was 85%. Overall, the malignancy prevalence is 2.2%. Of the malignancies, 20 are lung carcinomas: 19 non-small-cell lung carcinomas (NSCLCs) (14 adenocarcinoma or bronchioalveolar carcinoma [BAC], 4 squamous carcinoma, and 1 large-cell carcinoma) and 1 small-cell carcinoma; 15 (78%) of the NSCLCs are Stage I. Fourteen patients underwent surgery (1 pneumonectomy, 9 lobectomies, and 4 segmentectomies). CONCLUSION: Our results confirm that LDCT identifies small, early-stage, resectable lung cancer in a high-risk population.