Predictive Performance of Cell-Free Nucleic Acid-Based Multi-Cancer Early Detection Tests: A Systematic Review

BACKGROUND

Cancer-screening tests that can detect multiple cancer types, or multi-cancer early detection (MCED) tests, have emerged recently as a potential new tool in decreasing cancer morbidity and mortality. Most MCED assays are based on detecting cell-free tumor DNA (CF-DNA) in the blood. MCEDs offer the potential for screening for cancer organ sites with high mortality, both with and without recommended screening. However, their clinical utility has not been established. Before clinical utility can be established, the clinical validity of MCEDs, i.e., their ability to predict cancer status, must be demonstrated. In this study we performed a systematic review of the predictive ability for cancer of cell-free-nucleic acid-based MCED tests.

CONTENT

We searched PubMed for relevant publications from January 2017 to February 2023, using MeSH terms related to multi-cancer detection, circulating DNA, and related concepts. Of 1811 publications assessed, 61 were reviewed in depth and 20 are included in this review. For almost all studies, the cancer cases were assessed at time of diagnosis. Most studies reported specificity (generally 95% or higher) and overall sensitivity (73% median). The median number of cancer types assessed per assay was 5. Many studies also reported sensitivity by stage and/or cancer type. Sensitivity generally increased with stage.

SUMMARY

To date, relatively few published studies have assessed the clinical validity of MCED tests. Most used cancer cases assessed at diagnosis, with generally high specificity and variable sensitivity depending on cancer type and stage. The next steps should be testing in the intended-use population, i.e., asymptomatic persons.

Pulmonary Nodules, Lung Cancer Screening, and Lung Cancer in the Medicare Population

BACKGROUND

Early detection of lung cancer through management of pulmonary nodules (PNs) may reduce lung cancer mortality. We assessed the relationship between PNs and lung cancer.

RESEARCH QUESTION

How common are PNs in the Medicare population? What is the rate of lung cancer after detection of PNs? What is the relative proportion of early-stage lung cancer diagnosed after reporting of PNs vs through low-dose CT (LDCT) scan screening?

STUDY DESIGN AND METHODS

Using the Surveillance Epidemiology and End Results Program-Medicare database, we defined two cohorts: those in the 5% sample with ≥ 12 months of Medicare Parts A and B coverage from 2014 through 2019 (5% sample cohort) and those with a diagnosis of lung cancer from 2015 through 2017 with coverage for the prior 18-month period (lung cancer cohort). We defined PNs as chest CT scans with accompanying codes of 793.11 (International Classification of Diseases [ICD], Ninth Revision) or R91.1 (ICD, Tenth Revision) denoting a solitary PN. Patients in the lung cancer cohort were classified by whether they had undergone LDCT scan screening and whether they had a diagnosis of PN or neither (reference) within 18 months before diagnosis. We compared cancer stage and survival across groups.

RESULTS

Of 627,547 patients in the 5% sample cohort, 5.0% demonstrated PNs over median of 5.0 years of follow-up. Cumulative 1- and 2-year lung cancer rates after initial PN diagnosis were 3.2% and 4.7%, respectively. Of 44,194 patients in the lung cancer cohort, 15.7%, 2.9%, and 81.4% were in the PN, LDCT scan, and reference groups, respectively. Of patients in the PN, LDCT scan, and reference groups, 58.1%, 50.3%, and 24.4% respectively, had disease of a localized stage. Among all patients with localized disease, 30.0% and 4.9% were in the PN and LDCT scan and groups, respectively. Three-year lung cancer-specific survival rates were 75.0%, 75.6%, and 49.4% for the PN, LDCT scan, and reference groups.

INTERPRETATION

Patients with lung cancer who received a diagnosis after identification of PNs tended to have localized disease. Of all patients with localized disease, almost one-third had PNs that were diagnosed previously, compared with 5% of patients who had undergone LDCT scan screening. PNs represent a relatively common presentation of potentially curable lung cancer.

Study design considerations for trials to evaluate multicancer early detection assays for clinical utility

Blood-based assays using various technologies and biomarkers are in commercial development for the purpose of detecting multiple cancer types concurrently at an early stage of disease. These multicancer early detection (MCED) assays have the potential to improve the detection of cancers, particularly those for which no current screening modality exists. However, the unknown clinical benefits and harms of using MCED assays for cancer screening necessitate the development and implementation of a randomized controlled trial (RCT) to ascertain their clinical effectiveness. This was the consensus of experts at a National Cancer Institute-hosted workshop to discuss initial design concepts for such a trial. Using these assays to screen simultaneously for multiple cancers poses novel uncertainties for patient care compared with conventional screening tests for single cancers, such as establishing the diagnostic workup to confirm the presence of cancer at any organ site; clarifying appropriate follow-up for a positive assay for which there is no definitive diagnosis; identifying potential harms such as overdiagnosis of indolent disease; determining clinically effective and efficient strategies for disseminating MCED screening in real-world practice; and understanding the ethical implications, such as potentially alleviating or exacerbating existing health disparities. These assays present new and complex challenges for designing an RCT. Issues that emerged from the meeting centered around the need for a flexibly designed, clinical utility RCT to rigorously capture the evidence required to fully understand the net benefit of this promising technology. Specific topic areas were endpoints, screening protocols, recruitment, diagnostic pathway, pilot phase, data elements, specimen collection, and ethical considerations.

Estimating stage-specific sensitivity for cancer screening tests

OBJECTIVES

When evaluating potential new cancer screening modalities, estimating sensitivity, especially for early-stage cases, is critical. There are methods to approximate stage-specific sensitivity in asymptomatic populations, both in the prospective (active screening) and retrospective (stored specimens) scenarios. We explored their validity via a simulation study.

METHODS

We fit natural history models to lung and ovarian cancer screening data that permitted estimation of stage-specific (early/late) true sensitivity, defined as the probability subjects screened in the given stage had positive tests. We then ran simulations, using the fitted models, of the prospective and retrospective scenarios. Prospective sensitivity by stage was estimated as screen-detected divided by screen-plus interval-detected cancers, where stage is defined as stage at detection. Retrospective sensitivity by stage was estimated based on cancers detected within specified windows before clinical diagnosis with stage defined as stage at clinical diagnosis.

RESULTS

Stage-specific true sensitivities estimated by the lung cancer natural history model were 47% (early) and 63% (late). Simulation results for the prospective setting gave estimated sensitivities of 81% (early) versus 62% (late). In the retrospective scenario, early/late sensitivity estimates were 35%/57% (1-year window) and 27%/49% (2-year window). In the prospective scenario, most subjects with negative early-stage screens presented as other than early-stage interval cases. Results were similar for ovarian cancer, with estimated prospective sensitivity much greater than true sensitivity for early stage, 84% versus 25%.

CONCLUSIONS

Existing methods for approximating stage-specific sensitivity in both prospective and retrospective scenarios are unsatisfactory; improvements are needed before they can be considered to be reliable.

15-Year Benefits of Sigmoidoscopy Screening on Colorectal Cancer Incidence and Mortality : A Pooled Analysis of Randomized Trials

BACKGROUND

The effectiveness of screening for colorectal cancer (CRC) by sex and age in randomized trials is uncertain.

OBJECTIVE

To evaluate the 15-year effect of sigmoidoscopy screening on CRC incidence and mortality.

DESIGN

Pooled analysis of 4 large-scale randomized trials of sigmoidoscopy screening.

SETTING

Norway, the United States, the United Kingdom, and Italy.

PARTICIPANTS

Women and men aged 55 to 64 years at enrollment.

INTERVENTION

Sigmoidoscopy screening.

MEASUREMENTS

Primary end points were cumulative incidence rate ratio (IRR) and mortality rate ratio (MRR) and rate differences after 15 years of follow-up comparing screening versus usual care in intention-to-treat analyses. Stratified analyses were done by sex, cancer site, and age at screening.

RESULTS

Analyses comprised 274 952 persons (50.7% women), 137 493 in the screening and 137 459 in the usual care group. Screening attendance was 58% to 84%. After 15 years, the rate difference for CRC incidence was 0.51 cases (95% CI, 0.40 to 0.63 cases) per 100 persons and the IRR was 0.79 (CI, 0.75 to 0.83). The rate difference for CRC mortality was 0.13 deaths (CI, 0.07 to 0.19 deaths) per 100 persons, and the MRR was 0.80 (CI, 0.72 to 0.88). Women had less benefit from screening than men for CRC incidence (IRR for women, 0.84 [CI, 0.77 to 0.91]; IRR for men, 0.75 [CI, 0.70 to 0.81]; P = 0.032 for difference) and mortality (MRR for women, 0.91 [CI, 0.77 to 1.17]; MRR for men, 0.73 [CI, 0.64 to 0.83]; P = 0.025 for difference). There was no statistically significant difference in screening effect between persons aged 55 to 59 years and those aged 60 to 64 years.

LIMITATION

Data from the U.K. trial were less granular because of privacy regulations.

CONCLUSION

This pooled analysis of all large randomized trials of sigmoidoscopy screening demonstrates a significant and sustained effect of sigmoidoscopy on CRC incidence and mortality for 15 years.

PRIMARY FUNDING SOURCE

Health Fund of South-East Norway.

PLCOjs, a FAIR GWAS web SDK for the NCI Prostate, Lung, Colorectal and Ovarian Cancer Genetic Atlas project

MOTIVATION

The Division of Cancer Epidemiology and Genetics (DCEG) and the Division of Cancer Prevention (DCP) at the National Cancer Institute (NCI) have recently generated genome-wide association study (GWAS) data for multiple traits in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Genomic Atlas project. The GWAS included 110 000 participants. The dissemination of the genetic association data through a data portal called GWAS Explorer, in a manner that addresses the modern expectations of FAIR reusability by data scientists and engineers, is the main motivation for the development of the open-source JavaScript software development kit (SDK) reported here.

RESULTS

The PLCO GWAS Explorer resource relies on a public stateless HTTP application programming interface (API) deployed as the sole backend service for both the landing page's web application and third-party analytical workflows. The core PLCOjs SDK is mapped to each of the API methods, and also to each of the reference graphic visualizations in the GWAS Explorer. A few additional visualization methods extend it. As is the norm with web SDKs, no download or installation is needed and modularization supports targeted code injection for web applications, reactive notebooks (Observable) and node-based web services.

AVAILABILITY AND IMPLEMENTATION

code at https://github.com/episphere/plco; project page at https://episphere.github.io/plco.

Adherence with protocol medication use and mortality from unrelated causes in a prevention trial

Several studies have shown that non-adherence to medication use is associated with lower use of preventive services and increased mortality. We aimed to study the relationship between initial adherence to medication use and mortality in the Prostate Cancer Prevention Trial (PCPT). The PCPT randomized men age 55 and over to a finasteride or placebo arm. Duration of treatment was seven years, followed by end-of-study prostate biopsy. Extended follow-up for mortality was performed by linkage to the National Death Index. Non-adherence was defined as taking under 80% of required pills during the first or second 6-month trial period. Proportional hazards models were used to assess the relationship between adherence and all-cause mortality (excluding prostate cancer deaths). Three models were developed as follows: Model I (controlling for demographics and trial arm), Model II (Model I factors plus specific medical conditions), Model III (Model II factors plus lifestyle factors). Of 18,667 men included in the analysis, 3082 (16.5%) were non-adherent. The most common reasons for non-adherence were side effects (33.9%) and forgetting to take pills (22%). Through 5 and 10 years of follow-up, 178 (5.9%) and 483 (15.7%) non-adherent men died versus 581 (3.7%) and 1887 (12.1%) adherent men. Hazard ratios (HRs) at 5 years were 1.62 (95% CI: 1.37-1.91), 1.55 (95% CI: 1.30-1.83) and 1.49 (95% CI: 1.25-1.76) for Models I-III. HRs at ten years were lower but still statistically significant. Non-adherence to taking protocol medications was associated with increased mortality from unrelated conditions.

Lung Nodule Malignancy Prediction in Sequential CT Scans: Summary of ISBI 2018 Challenge

Lung cancer is by far the leading cause of cancer death in the US. Recent studies have demonstrated the effectiveness of screening using low dose CT (LDCT) in reducing lung cancer related mortality. While lung nodules are detected with a high rate of sensitivity, this exam has a low specificity rate and it is still difficult to separate benign and malignant lesions. The ISBI 2018 Lung Nodule Malignancy Prediction Challenge, developed by a team from the Quantitative Imaging Network of the National Cancer Institute, was focused on the prediction of lung nodule malignancy from two sequential LDCT screening exams using automated (non-manual) algorithms. We curated a cohort of 100 subjects who participated in the National Lung Screening Trial and had established pathological diagnoses. Data from 30 subjects were randomly selected for training and the remaining was used for testing. Participants were evaluated based on the area under the receiver operating characteristic curve (AUC) of nodule-wise malignancy scores generated by their algorithms on the test set. The challenge had 17 participants, with 11 teams submitting reports with method description, mandated by the challenge rules. Participants used quantitative methods, resulting in a reporting test AUC ranging from 0.698 to 0.913. The top five contestants used deep learning approaches, reporting an AUC between 0.87 - 0.91. The team's predictor did not achieve significant differences from each other nor from a volume change estimate (p =.05 with Bonferroni-Holm's correction).

Abstract 2570: Evaluation of aspirin use with cancer incidence and survival among older adults in the prostate, lung, colorectal, and ovarian cancer screening trial

Many studies have evaluated the long-term benefits of aspirin use, however the association between aspirin use and cancer incidence and survival in older individuals remains uncertain. Additional epidemiologic evidence of this association is necessary to better understand any possible protective effects of aspirin in older adults. We performed a post-hoc retrospective analysis of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, investigating the association of aspirin use with the risk of cancer incidence and survival from bladder, breast, esophageal, gastric, pancreatic, and uterine cancers among individuals age 65 and older. PLCO participants were included in the current study if (1) they were age 65 or over at baseline or survived to at least age 65 after enrollment and (2) had a valid baseline questionnaire with completed aspirin use information. Incident cancers were defined as first cancers diagnosed during cohort follow-up. Follow-up time began at the time of randomization or when the participant turned 65, whichever occurred first, and continued until the date of the cancer diagnosis, participant death, or the end of the study follow-up. Among participants diagnosed with the above incident cancers, the association of aspirin use prior to diagnosis with subsequent cancer-specific survival was evaluated. Follow-up for this analysis began at the time of diagnosis and ended at death or end of study follow-up. A total of 154,897 individuals were enrolled in the PLCO Trial. Of these, 139,896 individuals (mean [SD] age at baseline, 66.4 [2.4] years; 71,884 [51.4%] women; 123,824 white non-Hispanic [88.5%]) were included in the current analysis. During the study period, 32,580 incident cancers (including 1,751 bladder, 4,552 breast, 332 esophageal, 397 gastric, 878 pancreatic, 716 uterine cancers) were reported. Neither any aspirin nor aspirin use ≥3 times/week was associated with incidence of any of the investigated cancer types. However, multivariable regression analyses demonstrated that aspirin use ≥3 times/week was associated with increased bladder (HR, 0.67; 95% CI, 0.51-0.88) and breast (HR, 0.75; 95% CI, 0.59-0.96), but not esophageal, gastric, pancreatic, or uterine, cancer-specific survival. A similar association with bladder (HR, 0.75; 95% CI, 0.58, 0.98) and breast (HR, 0.79; 95% CI, 0.63, 0.99) cancer survival was observed with any aspirin use. In conclusion, any aspirin use and aspirin use ≥3 times/week was associated with improved bladder and breast cancer survival. The results of the current study provide suggestive observational evidence of the potential of aspirin use to improve bladder and breast cancer survival, however additional, follow-up studies are warranted.

Citation Format: Holli A. Loomans-Kropp, Paul Pinsky, Asad Umar. Evaluation of aspirin use with cancer incidence and survival among older adults in the prostate, lung, colorectal, and ovarian cancer screening trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2570.

Evaluation of Aspirin Use With Cancer Incidence and Survival Among Older Adults in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

IMPORTANCE

Many studies have evaluated the long-term benefits of aspirin use; however, the association of aspirin use with cancer incidence and survival in older individuals remains uncertain. Additional population-based evidence of this association is necessary to better understand any possible protective effects of aspirin in older adults.

OBJECTIVE

To investigate the association of aspirin use with risk of developing new cancers and site-specific cancer-associated survival in bladder, breast, esophageal, gastric, pancreatic, and uterine cancers.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Participants were aged 65 years or older at baseline (1993-2001) or reached age 65 during follow-up. Data analysis was conducted from January to June 2020.

MAIN OUTCOMES AND MEASURES

Incidence of and survival from the investigated cancer types. Univariable and multivariable hazard ratios (HRs) and 95% CIs were calculated using Cox proportional hazards regression modeling, adjusting for covariates. Multivariable models for incidence included time-varying covariates.

RESULTS

A total of 139 896 individuals (mean [SD] age at baseline, 66.4 [2.4] years; 71 884 [51.4%] women; 123 824 [88.5%] non-Hispanic White individuals) were included in the analysis. During the study period, 32 580 incident cancers (1751 [5.4%] bladder, 4552 [14.0%] breast, 332 [1.0%] esophageal, 397 [1.2%] gastric, 878 [2.7%] pancreatic, and 716 [2.2%] uterine cancers) were reported. Aspirin use was not associated with incidence of any of the investigated cancer types among individuals aged 65 years or older. Multivariable regression analysis demonstrated that aspirin use at least 3 times/week was associated with increased survival among patients with bladder (HR, 0.67; 95% CI, 0.51-0.88) and breast (HR, 0.75; 95% CI, 0.59-0.96) cancers but not among those with esophageal, gastric, pancreatic, or uterine cancer. A similar association of any aspirin use with bladder (HR, 0.75; 95% CI, 0.58-0.98) and breast (HR, 0.79; 95% CI, 0.63-0.99) cancer survival was observed.

CONCLUSIONS AND RELEVANCE

In the current study, any aspirin use and aspirin use at least 3 times/week was associated with improved bladder and breast cancer survival. Associations between aspirin use and incidence of any of the investigated cancers or between aspirin use and esophageal, gastric, pancreatic, or uterine cancer survival were not observed.

MRI-Targeted, Systematic, and Combined Biopsy for Prostate Cancer Diagnosis

BACKGROUND

The use of 12-core systematic prostate biopsy is associated with diagnostic inaccuracy that contributes to both overdiagnosis and underdiagnosis of prostate cancer. Biopsies performed with magnetic resonance imaging (MRI) targeting may reduce the misclassification of prostate cancer in men with MRI-visible lesions.

METHODS

Men with MRI-visible prostate lesions underwent both MRI-targeted and systematic biopsy. The primary outcome was cancer detection according to grade group (i.e., a clustering of Gleason grades). Grade group 1 refers to clinically insignificant disease; grade group 2 or higher, cancer with favorable intermediate risk or worse; and grade group 3 or higher, cancer with unfavorable intermediate risk or worse. Among the men who underwent subsequent radical prostatectomy, upgrading and downgrading of grade group from biopsy to whole-mount histopathological analysis of surgical specimens were recorded. Secondary outcomes were the detection of cancers of grade group 2 or higher and grade group 3 or higher, cancer detection stratified by previous biopsy status, and grade reclassification between biopsy and radical prostatectomy.

RESULTS

A total of 2103 men underwent both biopsy methods; cancer was diagnosed in 1312 (62.4%) by a combination of the two methods (combined biopsy), and 404 (19.2%) underwent radical prostatectomy. Cancer detection rates on MRI-targeted biopsy were significantly lower than on systematic biopsy for grade group 1 cancers and significantly higher for grade groups 3 through 5 (P<0.01 for all comparisons). Combined biopsy led to cancer diagnoses in 208 more men (9.9%) than with either method alone and to upgrading to a higher grade group in 458 men (21.8%). However, if only MRI-target biopsies had been performed, 8.8% of clinically significant cancers (grade group ≥3) would have been misclassified. Among the 404 men who underwent subsequent radical prostatectomy, combined biopsy was associated with the fewest upgrades to grade group 3 or higher on histopathological analysis of surgical specimens (3.5%), as compared with MRI-targeted biopsy (8.7%) and systematic biopsy (16.8%).

CONCLUSIONS

Among patients with MRI-visible lesions, combined biopsy led to more detection of all prostate cancers. However, MRI-targeted biopsy alone underestimated the histologic grade of some tumors. After radical prostatectomy, upgrades to grade group 3 or higher on histopathological analysis were substantially lower after combined biopsy. (Funded by the National Institutes of Health and others; Trio Study ClinicalTrials.gov number, NCT00102544.).

Thyroid Incidentalomas in Association With Low-Dose Computed Tomography in the National Lung Screening Trial

Advances in cancer screening methods have opened avenues for incidental findings and cancer overdiagnosis. We performed a secondary analysis of the National Lung Screening Trial (enrollment from 2002-2004), a randomized controlled trial comparing low-dose computed tomography (LDCT; n = 26,722) with chest radiography (CXR; n = 26,732) for lung cancer detection, to examine incidental findings related to thyroid cancer (ThCa). Three screening rounds were included, and median follow-up was 6.6 years for LDCT and 6.5 years for CXR. Radiologists reported lung and non-lung-related abnormalities. In the LDCT arm, 5.7%, 4.7%, and 4.5% of participants had abnormalities above the diaphragm (AADs) detected at baseline, year 1, and year 2, respectively, compared with 2.3%, 1.5%, and 1.3% in the CXR arm. In the LDCT arm, 205 AADs (7.0%) were thyroid-related. Overall, 60 ThCas were reported, 35 in the LDCT arm and 25 in the CXR arm (P = 0.2). In the LDCT arm, participants with a prior AAD had a 7.8-fold increased risk (95% confidence interval: 4.0, 15.1) of ThCa compared with those who did not have an AAD. Early and persistent excess of ThCas diagnosed earlier in the LDCT arm suggests overdiagnosis. The use of sensitive screening modalities for early detection of lung cancer might result in the discovery of thyroid incidentalomas.

Association of Aspirin Use With Mortality Risk Among Older Adult Participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

IMPORTANCE

Aspirin use has been associated with reduced risk of cancer mortality, particularly of the colorectum. However, aspirin efficacy may be influenced by biological characteristics, such as obesity and age. With the increasing prevalence of obesity and conflicting data regarding the effect of aspirin in older adults, understanding the potential association of aspirin use with cancer mortality according to body mass index (BMI) and age is imperative.

OBJECTIVES

To investigate the association of aspirin use with risk of all-cause, any cancer, gastrointestinal (GI) cancer, and colorectal cancer (CRC) mortality among older adults and to perform an exploratory analysis of the association of aspirin use with mortality stratified by BMI.

DESIGN, SETTING, PARTICIPANTS

This cohort study evaluated aspirin use among participants aged 65 years and older in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial at baseline (November 8, 1993, to July 2, 2001) and follow-up (2006-2008). Analysis began in late 2018 and was completed in September 2019.

MAIN OUTCOMES AND MEASURES

All-cause, any cancer, GI cancer, or CRC mortality. Multivariable hazard ratios (HRs) and 95% CIs were calculated using time-varying Cox proportional hazards regression modeling, adjusting for additional factors.

RESULTS

A total of 146 152 individuals (mean [SD] age at baseline, 66.3 [2.4] years; 74 742 [51.1%] women; 129 446 [88.6%] non-Hispanic white) were included in analysis. The median (interquartile range) follow-up time was 12.5 (8.7-16.4) years, encompassing 1 822 164 person-years. Compared with no use, aspirin use 1 to 3 times per month was associated with reduced risk of all-cause mortality (HR, 0.84; 95% CI, 0.80-0.88; P < .001) and cancer mortality (HR, 0.87; 95% CI, 0.81-0.94; P < .001). Aspirin use 3 or more times per week was associated with decreased risk of mortality of all causes (HR, 0.81; 95% CI, 0.80-0.83; P < .001), any cancer (HR, 0.85; 95% CI, 0.81-0.88; P < .001), GI cancer (HR, 0.75; 95% CI, 0.66-0.84; P < .001), and CRC (HR, 0.71; 95% CI, 0.61-0.84; P < .001). When stratified by BMI (calculated as weight in kilograms divided by height in meters squared), aspirin use 3 or more times per week among individuals with BMI 20 to 24.9 was associated with reduced risk of all-cause mortality (HR, 0.82; 95% CI, 0.78-0.85; P < .001) and any cancer mortality (HR, 0.86; 95% CI, 0.79-0.82; P < .001). Among individuals with BMI 25 to 29.9, aspirin use 3 or more times per week was associated with reduced risk of all-cause mortality (HR, 0.82; 95% CI, 0.79-0.85; P < .001), any cancer mortality (HR, 0.86; 95% CI, 0.81-0.91; P < .001), GI cancer mortality (HR, 0.72; 95% CI, 0.60-0.86; P < .001), and CRC mortality (HR, 0.66; 95% CI, 0.51-0.85; P = .001).

CONCLUSIONS AND RELEVANCE

In this cohort study, aspirin use 3 or more times per week was associated with a reduction in all-cause, cancer, GI cancer and CRC mortality in older adults.

Long-term cancer risk associated with lung nodules observed on low-dose screening CT scans

OBJECTIVE

Non-calcified nodules (NCNs) associated with false positive low-dose CT (LDCT) lung cancer screens have been attributed to various causes. Some, however, may represent lung cancer precursors. An association of NCNs with long-term lung cancer risk would provide indirect evidence of some NCNs being cancer precursors.

METHODS

LDCT arm participants in the National Lung Screening Trial (NLST) received LDCT screens at baseline and years 1-2. The relationship between NCNs found on LDCT screens and subsequent lung cancer diagnosis over different time periods was examined at the person and lobe level. For the latter, a lobe had a cancer outcome only if the cancer was located in the lobe. Separate analyses were performed on baseline and post-baseline LDCT findings; for the latter, those with baseline NCNs were excluded and only new (non-pre-existing) NCNs examined. Raw and adjusted rate-ratios (RRs) were computed for presence of NCNs and subsequent lung cancer risk; adjusted RRs controlled for demographic and smoking factors.

RESULTS

26,309 participants received the baseline LDCT screen. Over median 11.3 years follow-up, 1675 lung cancers were diagnosed. Adjusted RRs for time periods 0-4, 4-8 and 8-12 years following the baseline screen were 5.1 (95 % CI:4.4-5.9), 1.5 (95 % CI:1.3-1.9) and 1.5 (95 % CI:1.2-1.8) at the person-level and 14.7 (95 % CI:12.6-17.2), 2.6 (95 % CI: 2.0-3.4) and 2.2 (95 % CI:1.6-2.9) at the lobe-level. 18,585 participants were included in the post-baseline analysis. Adjusted RRs for periods 0-4, 4-8 and 8-11 years were 5.6 (95 % CI: 4.5-7.0), 1.9 (95 % CI: 1.3-2.7) and 1.6 (95 % CI: 0.9-2.9) at the person-level and 19.6 (95 % CI:14.9-25.3), 2.5 (95 % CI:1.3-4.7) and 3.3 (95 % CI:1.4-7.6) at the lobe-level. Raw RRs were similar.

CONCLUSION

NCNs are associated with excess long-term lung cancer risk, suggesting that some may be lung cancer precursors.

Abstract B034: Time to treatment and overall survival among men with localized prostate cancer

Background: Prostate cancer is the second most common cancer diagnosed among men in the United States. Delays from the time of confirmed diagnosis to primary treatment are more common for prostate compared to other malignancies. The objective of this study was to investigate factors associated with time to treatment and the effect of time to treatment on overall survival among men with early-stage prostate cancer.

Methods: From the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, men diagnosed with localized prostate cancer who received treatment within a year of diagnosis were selected for analysis (N=6,349). Selected men had date of diagnosis, treatment date, and mortality status as of 2012. We investigated sociodemographic and clinical factors associated with time to treatment using Cox regression. We also used Cox regression to examine the effect of time to treatment on overall survival. Covariates included Gleason score, PSA level, age at diagnosis, employment status, education level, race, marital status, and comorbidity burden.

Results: The median time to treatment was 73 (IQR: 44-120) days. Demographic factors associated with longer time to treatment included being Black (adjusted hazard ratio (aHR)= 0.85, 95%CI: 0.76-0.95), having some college education (aHR= 0.91, 95%CI: 0.85-0.97), and having a baccalaureate degree or a post-baccalaureate degree (aHR= 0.89, 95% CI: 0.84-0.95). Clinical factors associated with longer time to treatment were being diagnosed at an older age (aHR= 0.86, 95%CI:0.80-0.93 for age of 70-74 years and aHR= 0.80, 95%CI: 0.74-0.87 for 75 year and older) and having an elevated PSA level (HR=0.89, 95%CI: 0.81-0.94 for third PSA quartile (6.11-9.0) and HR=0.87, 95%CI: 0.81-0.94 for fourth PSA quartile (9.0 and above). Gleason score and comorbidity burden were not associated with time to treatment. Being married (aHR=1.11, 95%CI: 1.03-1.19) and being retired (aHR=1.09, 95%CI:1.034-1.16) were associated with shorter time to treatment. After adjusting for sociodemographic and clinical characteristics, time to treatment did not have a significant effect on overall survival.

Conclusions: College education, being Black, older age at diagnosis, and higher PSA levels were associated with longer time to treatment. Being married and being retired were associated with shorter time to treatment. Longer time to treatment was not associated with overall mortality among PLCO men with localized prostate cancer.

Citation Format: Dudith Pierre-Victor, Paul Pinsky, Iman K. Martin, Worta McCaskill-Stevens. Time to treatment and overall survival among men with localized prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B034.

Characteristics and Outcomes of Small Cell Lung Cancer Detected by CT Screening

BACKGROUND

Previous studies with a limited number of patients have reported divergent findings on whether screening can detect small cell lung cancer (SCLC) at an earlier stage and whether there might be a survival benefit.

METHODS

This study examined the characteristics of SCLC detected by using low-dose CT (LDCT) screening in the National Lung Screening Trial, a randomized study of individuals at high risk for developing lung cancer comparing LDCT imaging vs chest radiography. SCLC was denoted as screen detected if diagnosed ≤ 1 year of a positive screen or after a longer period but with no time gap between diagnostic procedures of > 1 year; interval detected if diagnosed ≤ 1 year of a negative screen; and nonscreen detected if the subject did not receive any screens or otherwise as postscreening.

RESULTS

A total of 143 cases of SCLC were diagnosed, including 49 (34.2%) screen detected, 15 (10.5%) interval detected, and 79 (55.2%) nonscreened/postscreening. Of the screening phase-diagnosed cases (ie, screen or interval detected), a higher proportion of SCLC cases compared with NSCLC cases were interval detected (23% vs 5%; P < .0001). A higher proportion of all SCLC cases compared with NSCLC cases were advanced stage (III/IV: 86% vs 36%; P < .0001). The unfavorable SCLC stage distribution extended across screen-detected (80% stage III/IV), interval-detected (86%), and nonscreened/postscreening (90%) cancers. Among screen-detected SCLC, only 63.3% had ≥ 1 noncalcified nodule in the cancer lobe compared with 85.4% of NSCLC cases (P < .0001). Even with very small LDCT screen-detected nodules, a high proportion of SCLC cases were late stage. There was no significant difference in survival between screen- and interval-detected or postscreening SCLC.

CONCLUSIONS

"Early detection" with the use of LDCT imaging had no impact on SCLC outcomes. A successful screening modality should ideally detect SCLC earlier than when it can be detected on LDCT scans.

Outcomes from ovarian cancer screening in the PLCO trial: Histologic heterogeneity impacts detection, overdiagnosis and survival

AIM

A mortality benefit from screening for ovarian cancer has never been demonstrated. The aim of this study was to evaluate the screening outcomes for different histologic subtypes of ovarian cancers.

METHODS

Women in the screening arm of the Prostate, Lung, Colorectal and Ovarian Screening Trial underwent CA-125 and transvaginal ultrasound annually for 3-5 years. We compared screening test characteristics (including overdiagnosis) and outcomes by tumour type (type II versus other) and study arm (screening versus usual care).

RESULTS

Of 78,215 women randomised, 496 women were diagnosed with ovarian cancer. Of the tumours that were characterised (n = 413; 83%), 74% (n = 305) were type II versus 26% other (n = 108). Among screened patients, 70% of tumours were type II compared to 78% in usual care (p = 0.09). Within the screening arm, 29% of type II tumours were screen detected compared to 54% of the others (p < 0.01). The sensitivity of screening was 65% for type II tumours versus 86% for other types (p = 0.02). 15% of type II screen-detected tumours were stage I/II, compared to 81% of other tumours (p < 0.01). The overdiagnosis rate was lower for type II compared to other tumours (28.2% versus 72.2%; p < 0.01). Ovarian cancer-specific survival was worse for type II tumours compared to others (p < 0.01). Survival was similar for type II (p = 0.74) or other types (p = 0.32) regardless of study arm.

CONCLUSIONS

Test characteristics of screening for ovarian cancer differed for type II tumours compared to other ovarian tumours. Type II tumours were less likely to be screen diagnosed, early stage at diagnosis or overdiagnosed.

The relationship of cancer characteristics and patient outcome with time to lung cancer diagnosis after an abnormal screening CT

PURPOSE

The National Lung Screening Trial (NLST) demonstrated a reduction in lung cancer and all-cause mortality with low-dose CT (LDCT) screening. The aim of our study was to examine the time to diagnosis (TTD) of lung cancer in the LDCT arm of the NLST and assess its relationship with cancer characteristics and survival.

METHODS

The subjects (N = 462) with a positive baseline screen and subsequent lung cancer diagnosis within 3 years were evaluated by data and image review to confirm the baseline abnormality. The cases were analysed for the relationship between TTD and imaging features, cancer type, stage and survival for 7 years from baseline screen.

RESULTS

Cancer was judged to be present at baseline in 397/462 cases. The factors that showed significant association (p value trend less than 0.05) with longer TTD included smaller nodule size, pure ground glass nodules (GGNs), smooth/lobulated margins, stages I/II, adenocarcinoma, and decreasing lung cancer mortality. The logistic regression model for lung cancer death showed significant inverse relationships with size less than 20 mm (OR = 0.32), pure GGNs (OR = 0.24), adenocarcinoma (OR = 0.57) and direct relationship with age (OR = 1.4).

CONCLUSION

TTD after a positive LDCT screen in the NLST showed a strong association with imaging features, stage and mortality.

KEY POINTS

• NLST observed variable time to lung cancer diagnosis from positive baseline screen. • Time to diagnosis was associated with imaging features, cancer type and stage. • In univariate but not multivariate analysis, longer TTD correlated with decreased mortality.

A re-analysis of the prostate, lung, colorectal, and ovarian (PLCO) cancer screening trial accounting for ovarian cancer (OVCA) heterogeneity

5564

Background: A mortality benefit from screening for OVCA has not been demonstrated, but screening efficacy could differ for histologic subtypes. We re-analyzed PLCO evaluating whether OVCA detection and outcomes were affected by the heterogeneous biologic behavior of this disease. Methods: Type 2 tumors (moderately/poorly differentiated serous and adenocarcinoma) were compared to all other tumor (OT) types (low grade serous and endometrioid, clear cell, other, low malignancy potential) (LMP). We examined differences in the distribution of tumor types and stage by study arm and method of diagnosis [screen detected (SD) and interval detected (ID) (i.e. assigned to screening but diagnosed between screening tests)]. Stage distribution and survival were analyzed. Results: Among the entire PLCO population, 531 women were diagnosed with OVCA during the study; 282 (53%) in the screening arm and 249 (47%) in the usual care arm. Of the tumors able to be characterized (n=408; 77%), 74% (n=300) were Type 2 and 26% OT (n=108). In the screening arm, 70% of tumors diagnosed were Type 2 compared to 78% in usual care (p=0.07). Overall, survival was significantly better for OT tumors compared to Type 2 tumors (p<0.01) but there was no difference in survival by study arm for either tumor type separately (Type 2: p=0.50; OT: p=0.23). Within the screening arm, 30% of Type 2 tumors were SD compared to 54% of OT tumors (p=0.02) (see Table). Only 15% of Type 2 SD tumors were Stage I/II, compared to 82% of SD OT tumors (p<0.01). Stage at diagnosis was similar among Type 2 patients whether they were SD or ID (p=0.56) and there was no difference in survival (p=0.56). Conclusions: A significant difference in tumor types by study arm was not observed. However, within the screening arm, Type 2 tumors were less likely to be SD or Stage I/II compared to OT tumors. Survival for Type 2 tumors was similar regardless of method of diagnosis. [Table: see text]

PLCO: Evolution of an Epidemiologic Resource and Opportunities for Future Studies

The Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), a large-scale, multi-institutional, randomized controlled trial, was launched in 1992 to evaluate the effectiveness of screening modalities for prostate, lung, colorectal, and ovarian cancer. However, PLCO was additionally designed to serve as an epidemiologic resource and the National Cancer Institute has invested substantial resources over the years to accomplish this goal. In this report, we provide a summary of changes to PLCO's follow-up after conclusion of the screening phase of the trial and highlight recent data and biospecimen collections, including ancillary studies, geocoding, administration of a new medication use questionnaire, consent for linkage to Medicare, and additional tissue collection that enhance the richness of the PLCO resource and provide further opportunities for scientific investigation into the prevention, early detection, etiology and treatment of cancer.

Abstract 1795: The feasibility study of a randomized cancer screening trial in China

Lung cancer has been the leading cause of cancer death in China since the 1990s and the disease burden likely will increase. The US National Lung Screening Trial (NLST) showed a 16-20% mortality reduction in a high-risk population that had undergone Low-Dose Computed Tomography (LDCT). China would like to confirm the main result from the US NLST in the Chinese population. The aim of this study is to obtain necessary information on performance of the organizations involved in designing, conducting, monitoring and managing the study. Another goal is to test colorectal cancer screening strategies in China. This is a first randomized trial on lung and colorectal cancer screening in China. The feasibility study will aid in the development of a practical design for the Randomized Cancer Screening Trial in China.

This study has been carried out in three cites (Changsha city, Hunan province; Lanzhou city, Gansu province; and Haining city, Zhejiang province) since August, 2014. Individuals at elevated risk of lung cancer were randomized into three arms: annual low-dose helical CT exams for three years (T0, T1, T2) and baseline colonoscopy (T0); two low-dose helical CT exams (T0, T2) plus annual faecal immunochemical test (OC-faecal immunochemical tests at T0, T1, T2); and annual InSure-faecal immunochemical tests combined with Septin 9 test (T0, T1, T2). All participants will be followed for at least three years from randomization to yield data relevant to answering the study objectives.

As of March 31, 2015, a total of 2696 eligible participants were enrolled at 3 cancer hospitals and randomly assigned to three study arms (894 in arm 1, 902 in arm 2, and 900 in arm 3). The gender distribution is 53% male and 47% female. Baseline characteristics of the study population by age, gender and total pack-year exposure were balanced. The rate of adherence to LDCT screening at the first round (T0) was 89.0%. 1598 participants received LDCT in the first round. The rate of abnormality was 77.4% with LDCT and 6.5% and 6.1% with suspicious for lung cancer for arm 1 and arm 2 respectively at T0. 2150 participants received colorectal cancer screening. The positivity was 34.1% with colonoscopy screening, 8.0% with OC-FIT test, 4.5% with InsureFIT test, and 5.8% with Septin9 test.

Citation Format: Ping Hu, Min Dai, Jufang Shi, Jiansong Ren, Jiang Li, Xianzhen Liao, Lingbin Du, Yuqing Liu, Zhaoli Chen, Ning Wu, Qian Liu, Paul Pinsky, Philip Prorok, Richard Fagerstrom, Martina Taylor, Barnett Kramer, Jie He. The feasibility study of a randomized cancer screening trial in China. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1795.

Lung cancer incidence and mortality in National Lung Screening Trial participants who underwent low-dose CT prevalence screening: a retrospective cohort analysis of a randomised, multicentre, diagnostic screening trial

BACKGROUND

Annual low-dose CT screening for lung cancer has been recommended for high-risk individuals, but the necessity of yearly low-dose CT in all eligible individuals is uncertain. This study examined rates of lung cancer in National Lung Screening Trial (NLST) participants who had a negative prevalence (initial) low-dose CT screen to explore whether less frequent screening could be justified in some lower-risk subpopulations.

METHODS

We did a retrospective cohort analysis of data from the NLST, a randomised, multicentre screening trial comparing three annual low-dose CT assessments with three annual chest radiographs for the early detection of lung cancer in high-risk, eligible individuals (aged 55-74 years with at least a 30 pack-year history of cigarette smoking, and, if a former smoker, had quit within the past 15 years), recruited from US medical centres between Aug 5, 2002, and April 26, 2004. Participants were followed up for up to 5 years after their last annual screen. For the purposes of this analysis, our cohort consisted of all NLST participants who had received a low-dose CT prevalence (T0) screen. We determined the frequency, stage, histology, study year of diagnosis, and incidence of lung cancer, as well as overall and lung cancer-specific mortality, and whether lung cancers were detected as a result of screening or within 1 year of a negative screen. We also estimated the effect on mortality if the first annual (T1) screen in participants with a negative T0 screen had not been done. The NLST is registered with ClinicalTrials.gov, number NCT00047385.

FINDINGS

Our cohort consisted of 26 231 participants assigned to the low-dose CT screening group who had undergone their T0 screen. The 19 066 participants with a negative T0 screen had a lower incidence of lung cancer than did all 26 231 T0-screened participants (371·88 [95% CI 337·97-408·26] per 100 000 person-years vs 661·23 [622·07-702·21]) and had lower lung cancer-related mortality (185·82 [95% CI 162·17-211·93] per 100 000 person-years vs 277·20 [252·28-303·90]). The yield of lung cancer at the T1 screen among participants with a negative T0 screen was 0·34% (62 screen-detected cancers out of 18 121 screened participants), compared with a yield at the T0 screen among all T0-screened participants of 1·0% (267 of 26 231). We estimated that if the T1 screen had not been done in the T0 negative group, at most, an additional 28 participants in the T0 negative group would have died from lung cancer (a rise in mortality from 185·82 [95% CI 162·17-211·93] per 100 000 person-years to 212·14 [186·80-239·96]) over the course of the trial.

INTERPRETATION

Participants with a negative low-dose CT prevalence screen had a lower incidence of lung cancer and lung cancer-specific mortality than did all participants who underwent a prevalence screen. Because overly frequent screening has associated harms, increasing the interval between screens in participants with a negative low-dose CT prevalence screen might be warranted.

FUNDING

None.

Laboratory detective work identifies a mishandling problem in sample aliquoting

Data from a recent ovarian cancer biomarker study using serum aliquots from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial Biorepository showed that CA125II concentrations in these aliquots were significantly lower than those previously measured in the same subjects from the same blood draw. We designed an experiment to investigate whether samples used in the study (reference study) were compromised during the aliquoting process. We measured CA125II in the "sister" vials created during the same aliquoting process as the reference study aliquot, and in "cousin" vials newly aliquoted from another parent vial from the same blood draw, from 15 healthy controls in the study. Because the sister vials were created in a specific order, we also assessed whether there was a CA125II concentration gradient among the sisters. The Wilcoxon signed-rank test was used to test the statistical significance of the observed differences. Mean CA125II concentration (volume-averaged) was greater in the sisters than the cousins in all 15 subjects (p<0.001). The mean coefficient of variation was 0.25 (range: 0.12-0.43) in the sisters and 0.11 (range: 0.-1.1) in the cousins (p<0.008). The mean ratio of CA125II in the 5(th) aliquoted versus the 3(rd) aliquoted sister vial was 1.66 (1.25-2.5, p<0.001). These data suggest that the parent vials were not adequately mixed before they were aliquoted. CA125II in serum can partially precipitate to form a concentration gradient in long-term storage. Rigorous vortexing after thawing and before aliquoting is thus critical.

Projected outcomes using different nodule sizes to define a positive CT lung cancer screening examination

BACKGROUND

Computed tomography (CT) screening for lung cancer has been associated with a high frequency of false positive results because of the high prevalence of indeterminate but usually benign small pulmonary nodules. The acceptability of reducing false-positive rates and diagnostic evaluations by increasing the nodule size threshold for a positive screen depends on the projected balance between benefits and risks.

METHODS

We examined data from the National Lung Screening Trial (NLST) to estimate screening CT performance and outcomes for scans with nodules above the 4mm NLST threshold used to classify a CT screen as positive. Outcomes assessed included screening results, subsequent diagnostic tests performed, lung cancer histology and stage distribution, and lung cancer mortality. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the different nodule size thresholds. All statistical tests were two-sided.

RESULTS

In 64% of positive screens (11598/18141), the largest nodule was 7 mm or less in greatest transverse diameter. By increasing the threshold, the percentages of lung cancer diagnoses that would have been missed or delayed and false positives that would have been avoided progressively increased, for example from 1.0% and 15.8% at a 5 mm threshold to 10.5% and 65.8% at an 8 mm threshold, respectively. The projected reductions in postscreening follow-up CT scans and invasive procedures also increased as the threshold was raised. Differences across nodules sizes for lung cancer histology and stage distribution were small but statistically significant. There were no differences across nodule sizes in survival or mortality.

CONCLUSION

Raising the nodule size threshold for a positive screen would substantially reduce false-positive CT screenings and medical resource utilization with a variable impact on screening outcomes.

Comparative analysis of 5 lung cancer natural history and screening models that reproduce outcomes of the NLST and PLCO trials

BACKGROUND

The National Lung Screening Trial (NLST) demonstrated that low-dose computed tomography screening is an effective way of reducing lung cancer (LC) mortality. However, optimal screening strategies have not been determined to date and it is uncertain whether lighter smokers than those examined in the NLST may also benefit from screening. To address these questions, it is necessary to first develop LC natural history models that can reproduce NLST outcomes and simulate screening programs at the population level.

METHODS

Five independent LC screening models were developed using common inputs and calibration targets derived from the NLST and the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO). Imputation of missing information regarding smoking, histology, and stage of disease for a small percentage of individuals and diagnosed LCs in both trials was performed. Models were calibrated to LC incidence, mortality, or both outcomes simultaneously.

RESULTS

Initially, all models were calibrated to the NLST and validated against PLCO. Models were found to validate well against individuals in PLCO who would have been eligible for the NLST. However, all models required further calibration to PLCO to adequately capture LC outcomes in PLCO never-smokers and light smokers. Final versions of all models produced incidence and mortality outcomes in the presence and absence of screening that were consistent with both trials.

CONCLUSIONS

The authors developed 5 distinct LC screening simulation models based on the evidence in the NLST and PLCO. The results of their analyses demonstrated that the NLST and PLCO have produced consistent results. The resulting models can be important tools to generate additional evidence to determine the effectiveness of lung cancer screening strategies using low-dose computed tomography.

Overdiagnosis in low-dose computed tomography screening for lung cancer

IMPORTANCE

Screening for lung cancer has the potential to reduce mortality, but in addition to detecting aggressive tumors, screening will also detect indolent tumors that otherwise may not cause clinical symptoms. These overdiagnosis cases represent an important potential harm of screening because they incur additional cost, anxiety, and morbidity associated with cancer treatment.

OBJECTIVE

To estimate overdiagnosis in the National Lung Screening Trial (NLST).

DESIGN, SETTING, AND PARTICIPANTS

We used data from the NLST, a randomized trial comparing screening using low-dose computed tomography (LDCT) vs chest radiography (CXR) among 53 452 persons at high risk for lung cancer observed for 6.4 years, to estimate the excess number of lung cancers in the LDCT arm of the NLST compared with the CXR arm.

MAIN OUTCOMES AND MEASURES

We calculated 2 measures of overdiagnosis: the probability that a lung cancer detected by screening with LDCT is an overdiagnosis (PS), defined as the excess lung cancers detected by LDCT divided by all lung cancers detected by screening in the LDCT arm; and the number of cases that were considered overdiagnosis relative to the number of persons needed to screen to prevent 1 death from lung cancer.

RESULTS

During follow-up, 1089 lung cancers were reported in the LDCT arm and 969 in the CXR arm of the NLST. The probability is 18.5% (95% CI, 5.4%-30.6%) that any lung cancer detected by screening with LDCT was an overdiagnosis, 22.5% (95% CI, 9.7%-34.3%) that a non-small cell lung cancer detected by LDCT was an overdiagnosis, and 78.9% (95% CI, 62.2%-93.5%) that a bronchioalveolar lung cancer detected by LDCT was an overdiagnosis. The number of cases of overdiagnosis found among the 320 participants who would need to be screened in the NLST to prevent 1 death from lung cancer was 1.38.

CONCLUSIONS AND RELEVANCE

More than 18% of all lung cancers detected by LDCT in the NLST seem to be indolent, and overdiagnosis should be considered when describing the risks of LDCT screening for lung cancer.

Diagnostic evaluation following a positive lung screening chest radiograph in the Prostate, Lung, Colorectal, Ovarian (PLCO) Cancer Screening Trial

Lung cancer is the major cause of cancer mortality. One of the aims of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) was to determine if annual screening chest radiographs reduce lung cancer mortality. We enrolled 154,900 individuals, aged 55-74 years; 77,445 were randomized to the intervention arm and received an annual chest radiograph for 3 or 4 years. Participants with a positive screen underwent diagnostic evaluation under guidance of their primary physician. Methods of diagnosis or exclusion of cancer, interval from screen to diagnosis, and factors predicting diagnostic testing were evaluated. One or more positive screens occurred in 17% of participants. Positive screens resulted in biopsy in 3%, with 54% positive for cancer. Biopsy likelihood was associated with a mass, smoking, age, and family history of lung cancer. Diagnostic testing stopped after a chest radiograph or computed tomography/magnetic resonance imaging in over half. After a second or subsequent positive screen, evaluation stopped after comparison to prior radiographs in over half. Of 308 screen-detected cancers, the diagnosis was established by thoracotomy/thoracoscopy in 47.7%, needle biopsy in 27.6%, bronchoscopy in 20.1% and mediastinoscopy in 2.9%. Eighty-four percent of screen-detected lung cancers were diagnosed within 6 months. Diagnostic evaluations following a positive screen were conducted in a timely fashion. Lung cancer was diagnosed by tissue biopsy or cytology in all cases. Lung cancer was excluded during evaluation of positive screening examinations by clinical or radiographic evaluation in all but 1.4% who required a tissue biopsy.

Evaluation of reader variability in the interpretation of follow-up CT scans at lung cancer screening

PURPOSE

To measure reader agreement in determining whether lung nodules detected at baseline screening computed tomography (CT) had changed at subsequent screening examinations and to evaluate the variability in recommendations for further follow-up.

MATERIALS AND METHODS

All subjects were enrolled in the National Lung Screening Trial (NLST), and each participant consented to the use of their de-identified images for research purposes. The authors randomly selected 100 cases of nodules measuring at least 4.0 mm at 1-year screening CT that were considered by the original screening CT reader to be present on baseline CT scans; nodules considered by the original reader to have changed were oversampled. Selected images from each case showing the entire nodule at both examinations were preloaded on a picture archiving and communication system workstation. Nine radiologists served as readers, and they evaluated whether the nodule was present at baseline and recorded the bidimensional measurements and nodule characteristics at each examination, presence or absence of change, results of screening CT, and follow-up recommendations (high-level follow-up, low-level follow-up, no follow-up).

RESULTS

On the basis of reviews during case selection, five nodules seen at follow-up were judged not to have been present at baseline; for 19 of the remaining 95 cases, at least one reader judged the nodule not to have been present at baseline. For the 76 nodules that were unanimously considered to have been present at baseline, 21%-47% (mean ± standard deviation, 30% ± 9) were judged to have grown. The κ values were similar for growth (κ = 0.55) and a positive screening result (κ = 0.51) and were lower for a change in margins and attenuation (κ = 0.27-0.31). The κ value in the recommendation of high- versus low-level follow-up was high (κ = 0.66).

CONCLUSION

Reader agreement on nodule growth and screening result was moderate to substantial. Agreement on follow-up recommendations was lower.

Abstract 3049: Overexpression of miR-17 family miRNAs in prostate cancer biopsies: Evidence for a stem-cell-like miRNA profile in high grade/high stage tumors

Complex changes in microRNA (miRNA) expression patterns have been observed in many different types of cancer, including prostate cancer. Although the consequences of deregulation of miRNA expression in human cancer are still largely unknown, the use of miRNAs for cancer classification and prognosis has emerged as an important new area of biomarker research. We compared the tissue expression of miRNAs in prostate biopsies from patients with high grade/high stage tumors with biopsies from patients with no evidence of malignancy. Snap frozen prostate biopsy samples were prospectively collected using tissue printing techniques and total RNA was isolated for miRNA analysis using Agilent miRNA microarrays (Version 1, containing 470 human tissue miRNAs). The prostate cancer cases included in the microarray profiling study had at least 5 of 12 cores positive for cancer and significant areas of Gleason 7 or more. The no-cancer controls showed no prostate cancer, HGPIN or suspicious histology in any of the 12 biopsy cores. In our analysis of miRNA expression patterns, “significant change in expression” was defined as at least 2 fold change and F test (p&lt;0.05). Three different internal reference normalization methods were used in the data analysis; here we classify miRNAs as “overexpressed” or “underexpressed” only when all three methods agree. In high grade/high stage biopsy cancer, 64 of the 470 human tissue miRNAs on the microarray (13.6%) were found to be significantly overexpressed when compared with miRNA expression in biopsies from no-cancer controls. This set of overexpressed miRNAs includes 4 of the 5 miR-200 family miRNAs that have been implicated in the regulation of the epithelial-to-mesenchymal transition (EMT). The cancer-overexpressed miRs also include 6 of the 8 miR-17 family genes; this miRNA family has been implicated in the control of stem-cell differentiation during embryogenesis. Interestingly, the 6 miR-17 family miRs that are overexpressed in high grade/high stage prostate cancer include 2 from each of the 3 polycistronic clusters that encode this highly conserved miR family, an expression pattern similar to the coordinated expression observed in early embryonic development. This robust stem-cell-like miRNA profile offers an interesting new candidate biomarker that may be particularly sensitive to an aggressive prostate cancer phenotype.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3049.

Transparency and reproducibility in data analysis: the Prostate Cancer Prevention Trial

With the analysis of complex, messy data sets, the statistics community has recently focused attention on "reproducible research," namely research that can be readily replicated by others. One standard that has been proposed is the availability of data sets and computer code. However, in some situations, raw data cannot be disseminated for reasons of confidentiality or because the data are so messy as to make dissemination impractical. For one such situation, we propose 2 steps for reproducible research: (i) presentation of a table of data and (ii) presentation of a formula to estimate key quantities from the table of data. We illustrate this strategy in the analysis of data from the Prostate Cancer Prevention Trial, which investigated the effect of the drug finasteride versus placebo on the period prevalence of prostate cancer. With such an important result at stake, a transparent analysis was important.

Ongoing colorectal cancer risk despite surveillance colonoscopy: the Polyp Prevention Trial Continued Follow-up Study

BACKGROUND

Despite regular colonoscopy, interval colorectal cancer (CRC) may occur. Long-term studies examining CRC rates in patients with previous colonoscopy are lacking.

OBJECTIVE

We examined the rate of interval CRC in the Polyp Prevention Trial Continued Follow-up Study (PPT-CFS), an observational study of PPT participants that began after the PPT ended.

DESIGN

Prospective.

SETTING

A national U.S. community-based polyp prevention trial.

MAIN OUTCOME MEASUREMENTS

Medical records of patients with CRC were collected, reviewed, and abstracted in a standardized fashion.

RESULTS

Among 2079 PPT participants, 1297 (62.4%) agreed to participate in the PPT-CFS. They were followed for a median of 6.2 years after 4.3 years of median follow-up in the main PPT. Nine cases of CRC were diagnosed over 7626 person-years of observation (PYO), for an incidence rate of 1.2/1000 PYO. The ratio of CRCs observed compared with that expected by Surveillance, Epidemiology, and End Results was 0.64 (95% CI, 0.28-1.06). Including all CRCs (N = 22) since the beginning of the PPT, the observed compared with expected rate by Surveillance, Epidemiology, and End Results was 0.74 (95% CI, 0.47-1.05). Of patients in whom CRC developed in the PPT-CFS, 78% had a history of an advanced adenoma compared with only 43% of patients who remained cancer free (P = .04).

LIMITATION

A relatively small number of interval cancers were detected.

CONCLUSIONS

Despite frequent colonoscopy during the PPT, in the years after the trial, there was a persistent ongoing risk of cancer. Subjects with a history of advanced adenoma are at increased risk of subsequent cancer and should be followed closely with continued surveillance.

Reliability and accuracy of the endoscopic appearance in the identification of aberrant crypt foci

BACKGROUND

Aberrant crypt foci (ACF) have emerged as a putative precursor to colorectal adenoma, with potential use as a biomarker of colorectal cancer. However, there are wide differences in ACF prevalence, dysplasia, and histologic confirmation rates across studies. These differences may, in part, be because of variability in identification of endoscopic criteria.

OBJECTIVE

To systematically evaluate the accuracy and reliability of various endoscopic criteria used to identify ACF when using magnification chromoendoscopy (MCE).

DESIGN

Images obtained via MCE were shown to participating endoscopists who diagnosed them as ACF or not and who assessed them for the endoscopic characteristics used to identify ACF in the literature.

MAIN OUTCOME MEASUREMENTS

The predictive ability of the endoscopic criteria (crypt number, staining, margin, crypt size, epithelial thickness, and lumen shape) for histologic confirmation of ACF, and their reliability across endoscopists. The accuracy of the examiners in identifying ACF that were histologically confirmed was also assessed.

RESULTS

The interrater agreement rate for all except one of the endoscopic criteria (crypt number) was low and did not improve with training. None of the criteria could significantly predict histologic confirmation of ACF. Despite training exercises, accuracy of endoscopists to correctly identify a histologically proven ACF remained low.

LIMITATIONS

Still images with x40 optical magnification were analyzed rather than real-time endoscopy. All ACF samples were hyperplastic; none were dysplastic.

CONCLUSIONS

No endoscopic criteria evaluated by our study predicted histologic confirmation of ACF. MCE had low accuracy and poor reliability.

The natural history of aberrant crypt foci

BACKGROUND

Aberrant crypt foci (ACF) are the putative precursors to colorectal adenomas and may be useful as biomarkers. Knowledge of their natural history is essential to understanding their potential utility.

OBJECTIVE

Our purpose was to examine ACF detection 1 year after initial observation.

DESIGN

We conducted a multicenter study of ACF by using a standardized protocol. ACF in the rectum were assessed and subjects returned 1 year later to evaluate the natural history of the lesions.

SETTING

Ancillary study to the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.

RESULTS

Of 78 subjects enrolled, 64 (82%) returned for a repeat examination 1 year later. The mean age was 71 years, 70% were male, and 54% had a history of adenomatous polyps. At the initial examination, 66% of subjects had at least 1 ACF detected in the rectum, with a mean of 2.1 +/- 2.3 per person. One year later, 60% of these subjects had at least 1 of the original ACF reidentified, but only 43% of all ACF were reidentified. A total of 56% of subjects had new ACF identified.

LIMITATIONS

These results are generated from the pilot phase. Improvements or change in technique over time could have influenced the results.

CONCLUSIONS

A total of 60% of subjects who had ACF continued to have at least one ACF 1 year later, but less than half the specific ACF could be reidentified, and more than 50% of subjects had new ACF. These results imply a considerable dynamic to ACF detection over a 1-year period of observation.

Estimating rates of true high-grade disease in the prostate cancer prevention trial

The Prostate Cancer Prevention Trial (PCPT) showed a decreased prostate cancer rate but an increased rate of high Gleason grade disease on biopsy for finasteride versus placebo. The results from radical prostatectomy (RP) on 25% of the men undergoing RP have recently been reported and suggest that grading artifacts in biopsy Gleason scoring may have occurred. We used a statistical model to extrapolate the RP Gleason results to all men in the PCPT using a missing-at-random assumption. We estimated the rates of true high-grade (Gleason 7-10) and true low-grade disease, where true Gleason grade is what is (or would have been) found on RP. We also estimated misclassification rates on biopsy of true high-grade and low-grade disease. We show that the rate of upgrading of biopsy low-grade disease to high-grade on RP is a function of misclassification rates as well as the ratio of true low-grade to high-grade disease. The estimated relative risks for true low-grade and true high-grade disease for finasteride compared with placebo were 0.61 (95% confidence interval, 0.51-0.71) and 0.84 (95% confidence interval, 0.68-1.05), respectively. The misclassification rate of true high-grade disease (to low-grade disease on biopsy) was significantly lower for finasteride (34.6%) than for placebo (52.6%). Although misclassification rates differed, upgrading rates were similar in each arm due to the different ratios of true low-grade to high-grade disease in each arm. Results from RP show that misclassification rates on biopsy were higher in the placebo arm and that the rate of true high-grade disease may have been lower in the finasteride arm.

GSTM1, GSTT1, and GSTP1 polymorphisms and risk of advanced colorectal adenoma

Cigarette smoking is a risk factor for colon adenoma. The glutathione S-transferase enzymes are involved in the detoxification of carcinogenic compounds including those found in tobacco smoke, and thus, may be important modifiers of individual risk of developing this disease. We examined the prevalence of GSTM1 and GSTT1 gene deletions, and two GSTP1 polymorphisms in 772 cases with advanced colorectal adenomas (>1 cm, villous elements or high-grade dysplasia) of the distal colon (descending or sigmoid colon or rectum) and 777 sigmoidoscopy negative controls enrolled in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Epidemiologic data on smoking was collected by self-administered questionnaire and DNA was extracted from whole blood or buffy coat. For GSTM1 and GSTT1, we used a newly developed TaqMan-based assay capable of discriminating heterozygous (+/-) individuals from those with two active alleles (+/+) and homozygous deletions (-/-). For GSTP1, the I105V and the A114V substitutions were identified using end point 5' nuclease assays (TaqMan). Adjusted odds ratios (OR) and 95% confidence intervals (95% CI) were determined using unconditional logistic regression, controlling for age, race, and gender. Advanced adenoma risk was increased in current/former smokers (OR, 1.4; 95% CI, 1.2-1.8). Risks were decreased in subjects with > or =1 inactive GSTM1 alleles (OR, 0.6; 95% CI, 0.4-0.9); and the association was independent of smoking status (P interaction = 0.59). Having > or =1 inactive GSTT1 allele was associated with increased risk among smokers (OR, 1.4; 95% CI, 1.1-1.9; P trend = 0.02) but not among never smokers (OR, 0.9; 95% CI, 0.6-1.3) and a significant interaction between smoking and genotype was observed (P interaction = 0.05). In summary, this is the first study to report associations between colorectal adenomas and GSTM1 wild-type and GSTT1 null allele among smokers. These findings only became apparent using a newly developed assay able to distinguish heterozygous from wild-type individuals. Our data provide evidence that phenotypic differences between these two groups exist.