Background
NCCN, the Centers for Medicare & Medicaid Services (CMS), and the US Preventive Services Task Force (USPSTF) recommend annual CT lung screening (CTLS) for current and former heavy smokers meeting the National Lung Screening Trial (NLST) entry criteria.1–4 All 3 organizations have expanded their screening recommendations to include older patients, younger patients, and/or patients with additional risk factors for lung cancer. Inclusion of these additional populations has generated controversy given the lack of formal evaluation in the NLST.5 The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Lung Cancer Screening, v1.2012, recommended annual CTLS for 2 groups of high-risk individuals1:
Group 1: Current smokers or former smokers who have quit within 15 years aged 55 to 74 years with a ≥30 pack-year smoking history (NLST population; NCCN category 1 recommendation).
Group 2: Current and former smokers aged ≥50 years with a ≥20 pack-year smoking history and at least one of the following additional lung cancer risk factors, not including secondhand smoke exposure (NCCN category 2B recommendation in v1.20121; currently a category 2A recommendation in v3.20186):
Personal history of smoking-related cancer
History of lung cancer in a first-degree relative
Occupational exposure to known lung carcinogens
Residential radon exposure (documented sustained and substantial)
Chronic lung disease, including emphysema and pulmonary fibrosis
Individuals in both NCCN group 1 and 2 should be potential candidates for definitive therapy and free of signs and symptoms of lung cancer.
In January 2012, in response to the NLST publication and the release of the NCCN Guidelines for Lung Cancer, our institution began offering clinical CTLS as a community benefit to all individuals meeting either NCCN group 1 or group 2 high-risk criteria. A comprehensive explanation of the design and implementation of our CTLS program, including recruitment, enrollment, and follow-up of participating individuals at high risk, was previously published.7 The present study compares demographic characteristics and screening metrics, including rates of positive findings, significant incidental findings, and malignancy, between our group 1 and 2 populations.
Methods
This retrospective single-center study was approved by the Lahey Hospital & Medical Center (LHMC) Institutional Review Board. We report results of consecutive individuals from LHMC who underwent clinical CTLS from January 1, 2012, through December 31, 2016. To qualify for screening, all individuals had to be at high risk for lung cancer according to the NCCN Guidelines, v1.2012; be asymptomatic; have a physician order for CTLS; be free of lung cancer for at least 5 years; and have no known metastatic disease. Continuing medical education events and decision support tools detailing the screening process and the NCCN group 1 and 2 high-risk criteria were made available to help ordering physicians conduct the CTLS shared decision-making visit.7 All CTLS examinations were performed on ≥64-row multidetector CT scanners at 100 kV and 30 to 100 mA depending on availability of iterative reconstruction software. Image interpretation was performed by radiologists credentialed in CTLS reporting using Lung-RADS, version 1.0 (LR).7,8 Examinations were classified as “negative” (LR 0, 1, and 2), “positive” (LR 3, LR 4A/B/X), or “suspicious” (LR 4A/B/X) based on LR criteria. Computer-aided detection software was not used. Group 1 and 2 screening results were analyzed based on round of screening, with T0 representing the baseline (prevalence) examination and T1, T2, and ≥T3, reflecting first, second, and ≥third annual incidence screening examinations. The next round of screening was defined as the examination following a negative result or the examination following the first negative examination after a positive result. Interval examinations performed to follow-up after a positive result were not included in this analysis.
Variables assessed included cancer detection rate (CDR), positive predictive value (PPV), suspicious predictive value (SPV), rate of infectious/inflammatory findings, rate of significant incidental findings, and false-negative rate. PPV and SPV were defined as the probability of a cancer diagnosis after either a positive or suspicious screening result, respectively, without an intervening negative examination in both cases. We defined a significant incidental finding as any unexpected new and/or unknown findings requiring clinical or imaging evaluation before the next CTLS examination. Given the high prevalence of coronary artery calcifications and emphysema in the CTLS population, these findings were not classified as significant incidentals (Table 1). Cancer diagnosis within 12 months of a negative examination resulted in classification of those results as a false-negative. All patients were followed for a minimum of 6 months, with follow-up ending on June 30, 2017, or until the date of the next annual screening round after December 31, 2016, whichever occurred first. P values for numerical/continuous variables were calculated using ANOVA. P values for categorical variables were determined using the chi-square test except in cases with <5 events, for which Fisher exact test was used. For all statistical analyses, the significance level for differences was set at P≤.05. All statistical analysis was performed using SPSS Statistics, version 21 (SPSS Inc.).
Results
Between January 1, 2012, and December 31, 2016, 3,449 qualified individuals from our institution were referred for CTLS; 814 (23.6%) did not meet group 1 criteria but did fulfill group 2 criteria (Figures 1 and 2). The most common reasons for not meeting group 1 criteria were aged <55 years (30.8%) and ≥15 quit-years (31.7%) (Figure 1). For individuals meeting group 2 criteria, the most common qualifying additional risk factors were chronic lung disease (32.4%) and a first-degree relative with lung cancer (31.7%)
Prevalence/Extent of CAC and Emphysema
A total of 2,927 patients (84.9%) underwent a baseline CTLS examination, with 698 of these (23.8%) in group 2. On average, patients in group 2 were slightly younger (60.6 vs 63.1 years; P<.001), smoked less (38.8 vs 50.8 pack-years; P<.001), quit for longer periods (18.1 vs 6.3 years; P<.001), were less likely to be current smokers (38.6% vs 55.8%; P<.001), and were less likely to have radiographically evident emphysema and/or coronary artery calcifications (83.6% vs 90.1%; P=.001) than group 1 (Tables 1 and 2). A total of 1,772, 1,094, and 689 patients underwent T1, T2, and ≥T3 annual incidence scans, respectively, with approximately 24% in group 2 at each incidence round (Table 3). Overall, 6,482 screening examinations were performed across all rounds of screening, with 1,555 (24.0%) in group 2. The average duration of follow-up was 30.4 months (group 1, 30.2 months; group 2, 31.3 months; P=.4) (Table 4).
Common reasons group 2 were ineligible for group 1.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Common reasons group 2 were ineligible for group 1.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Common reasons group 2 were ineligible for group 1.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Overall positive rates were 12.7%, 6.7%, 5.9%, and 6.0% at T0, T1, T2, and ≥T3 screening rounds, respectively, with no significant difference between group 1 and 2 (Table 3). There was also no significant difference in rates of suspicious examinations, false negatives, or infectious/inflammatory findings at each round of screening (Tables 3 and 5). An excess of significant incidental findings in group 1 was found in the T1 round of screening (3.0% vs 1.2%; P=.03), with no significant difference in other screening rounds (Table 5).
A total of 113 lung cancers were diagnosed during the study interval, with 28 (24.8%) in group 2 (Tables 4 and 6). Overall CDRs were 2.3%, 1.6%, 1.0%, and 1.2% in the T0, T1, T2, and ≥T3 rounds, respectively, yielding PPVs between 15% and 22% and SPVs between 29% and 44%. Although there were significantly increased CDRs in group 2 in the T2 round (2.7% vs 0.5% for group 1; P=.005), there was no difference between groups for these metrics in the other screening rounds or overall (1.8% vs 1.7%; P=.84). Group 2 patients tended to have early-stage disease (92.6% vs
Qualifying risk factors for group 2.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Qualifying risk factors for group 2.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Qualifying risk factors for group 2.
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 16, 4; 10.6004/jnccn.2018.7021
Patient Demographicsa
Discussion
Although smoking and age are the leading risk factors for development of lung cancer, other modifiable and hereditary risk factors may place individuals at equivalent or higher risk than the NLST population (group 1).1,9–12 In an effort to maximize the lifesaving potential of CTLS, several organizations, including CMS, USPSTF, the American Association for Thoracic Surgery, and NCCN, have selectively expanded their screening recommendations to include high-risk individuals who do meet the NLST criteria despite the limited research and empirical evidence for screening efficacy in these groups.1–3,9 The NCCN Guidelines for Lung Cancer Screening have been periodically reviewed and revised since their inception in October 2011 to account for new evidence and changes in accepted approaches to treatment. The most recent version (v3.2018) expands the original qualifying group 2 additional risk factors to include any combination of factors (excluding secondhand smoke exposure), which increases the risk of lung cancer diagnosis within 6 years to ≥1.3% for all current and former smokers aged ≥50 years with a ≥20 pack-year smoking history.6
In our single-center 5-year experience screening NCCN group 1 and 2 high-risk individuals, we found that nearly all CTLS metrics for both NCCN groups across ≥4 rounds of screening were similar, including rate of positive examination results, significant incidental findings, cancer detection, and false negatives, despite significantly lower smoking-related risk factors in the group 2 population at program entry (lower age, fewer pack-years, longer smoking cessation duration, and higher quit rates). These findings suggest that the addition of at least one of the NCCN-specified risk factors may compensate for any incremental decreased risk resulting from the lower age and smoking exposure in group 2 at program entry.
Many other CTLS program metrics were also similar between groups 1 and 2, including the likelihood of undergoing baseline screening following a qualified referral (84.9%). In addition, there was a stable percentage of patients in group 2 (24%) participating in each subsequent round of screening. Even the rate of infectious and inflammatory findings in these groups across all screening rounds (≈7%) was the same. These similarities likely reflect the uniform process of our CTLS program staff, particularly regarding scheduling, pretest disclosure of the need to be asymptomatic, and posttest result notification and follow-up.13
As expected, the CDR in our program was highest at baseline screening (2.3% and 2.0% in groups 1 and 2, respectively; P=.61). Interestingly, the overall CDR remained >1% for all incidence rounds of screening, including the fourth and later rounds, which were not assessed by the NLST (T0, T1, and T2 rounds only).4 Although there was a significantly
CLTS Metrics by Screening Round: Examination Results
Malignancy Rates
Our group 2 patients were more likely to be diagnosed with early-stage (≤II) non–small cell lung cancer (92.6% vs 80.3%; P=.66) and adenocarcinoma histology (67.9% vs 49.4%; P=.37); however, these trends did not reach statistical significance possibly due to small sample size. Differences in stage and histology may relate to differences in smoking-related risk factors and would appear to in part explain the higher rate of no evidence of disease after treatment observed in group 2, although this trend also did not reach statistical significance (78.6% vs 57.6%; P=.36).
For every 3 patients in group 1 in our CTLS program, we enrolled 1 patient in group 2. Given the estimated size of group 1 at 7 million Americans, this suggests that there could be as many as 2 million Americans in group 2 at high-risk for lung cancer who do not meet either CMS or USPSTF eligibility criteria.1,2,4 If our results are reproducible across the variety of institutions performing CTLS nationwide, expanding CMS and USPSTF eligibility to include patients in group 2 has the potential to save thousands of additional lives every year.15
Conclusions
We provide empirical evidence of screening efficacy in the NCCN group 2 population at a single institution. Although there were significant differences in smoking history and age at program entry, nearly all screening metrics for both NCCN group 1 and 2 were similar across ≥4 rounds of screening. Multiinstitutional investigation of group 2 is warranted to confirm similar results are broadly achievable.
CTLS appears to be equally effective in NCCN group 1 and 2 high-risk populations. Expanding national CTLS eligibility to include the NCCN group 2 population offers the potential to save thousands of additional lives each year.
CTLS Metrics by Screening Round: Other Results
CTLS Metrics by Screening Round: CDR, PPV, and SPV
The authors have disclosed that they have no financial interests, arrangements, affiliations, or commercial interests with the manufacturers of any products discussed in this article or their competitors.
See JNCCN.org for supplemental online content.
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