Elsevier

Lung Cancer

Volume 56, Issue 2, May 2007, Pages 193-199
Lung Cancer

Comparison of pathologic findings of baseline and annual repeat cancers diagnosed on CT screening

https://doi.org/10.1016/j.lungcan.2006.12.001Get rights and content

Summary

Screening for lung cancer produces two groups of lung cancers. Baseline cases include all prevalent cases with the expectation that slower-growing cancers and those that have achieved higher stage will be found in greater frequency. Repeat examination is expected to detect those cancers which have crossed the threshold for detection during the screening interval – 1 year in this study – and these are typically more rapidly growing cancers. The two groups encompass the full spectrum of lung cancers. Comparison of the baseline and annual repeat cases revealed differences in types of lung cancer. There were 202 baseline-detected cancers spanning the spectrum of pulmonary neoplasms with some slowly growing, some rapidly progressive and some at high stage; the 48 annual repeat cancers also included a spectrum of lung cancers but with more of the rapidly growing types, and more closely approximated the clinical spectrum of lung cancers. The NE carcinomas showed this trend best; small-cell carcinomas were under-represented and typical carcinoids were only found in the baseline group. Repeat cancers were found to grow rapidly, were typically smaller, less often multiple and the adenocarcinomas were less often pure BAC and less frequently contained a BAC component when invasive. The baseline adenocarcinomas included most of the BAC's, which is a diagnosis that requires special attention to its WHO definition. AAH was found to be frequently associated with adenocarcinoma, particularly BAC. Both baseline and annual repeat cases had a high percentage of invasive carcinomas with comparably high rates of resectability, high rates of node negativity and consequently a high proportion of cases in low stage.

Introduction

Screening for lung cancer is pursuit of its early diagnosis, before symptoms or overt signs appear. It is a repetitive process beginning with baseline screening of the entire cohort followed by periodic repeat screenings of the remaining cohort after baseline and clinically evident cases have been removed. The two groups contain the spectrum of lung cancer with the repeat screen tending to resemble that of lung cancer in general and the baseline screen containing a broad spectrum enriched by cancers, which are more slowly growing. Comparison of the histology of the two groups provides information on the anticipated composition of cases discovered by baseline and repeat screening with this protocol.

Reports of previous lung cancer screening studies, primarily the Early Lung Cancer Detection Project [1], [2], [3] have indicated that baseline (prevalent) cases include a higher frequency of slower-growing cancers as well as those that have achieved higher stage; repeat examination detects those cancers which crossed the threshold for detection during the screening interval, and detects a greater proportion of more rapidly growing cancers. Those previously reported studies were done in the 1970's, relied on sputum cytology and chest X-rays and, not surprisingly, detected a higher proportion of squamous cell carcinomas, many of which were endobronchial. Over the past 30 years, there has been a relative shift in cell type with adenocarcinoma replacing squamous cell carcinoma as the dominant cell type [4], [5], [6], [7], [8].

We have previously reported on the pathologic features of resected lung cancers diagnosed as a result of baseline CT screening in ELCAP [9] which were described in detail according to the ELCAP pathology protocol [10], [11]. CT scans of the chest were employed as the primary screening tool in the ELCAP studies and were especially effective in detecting small and early cases of lung cancer [12], [13].

Section snippets

Methods

Included in this report are all diagnosed cases of lung cancer identified in ELCAP [14] and NY-ELCAP [15] resulting from 10,056 baseline and 14,678 annual repeat screenings. All 10,056 participants gave an informed consent to the screening and to subsequent follow-up as detailed. Criteria for enrollment were the same for the original 1000 ELCAP [12] and all the NY-ELCAP [15] participants: age 60 and older, a history of at least 10 pack-years of cigarette smoking, no prior history of cancer

Results

A total of 250 people were diagnosed as having lung cancer as a result of screening, 202 resulting from baseline screening and 48 from annual repeat screening. Median age at the time of diagnosis was 69 years (range 49–85) and median pack-years of smoking 50 years (2–127). The frequency of N0M0 cases was slightly higher, although not significantly, in baseline than in repeat screening (169/202 = 84% versus 38/48 = 79%, P = 0.46). Of the 250 cases of cancer, 158 (63%) presented as a solid nodule; it

Discussion

This is the largest series available to date of CT screen-diagnosed lung cancers performed according to a common protocol, in which baseline and annual repeat cases are reported. The resection rate – a major determinant of curability – was similar in the two groups: 86% (174/202) for the baseline cases and 77% (37/48) for the annual repeat cases. Lobectomy was the treatment of choice, with 79% of baseline and 78% of repeat resections involving removal of a lobe. Bilobectomy and pneumonectomy

Conclusions

CT examination of the chest, at the intervals used and with the algorithms employed, appeared to be an effective tool for screening for lung cancer in the United States. Rates of resection and node negative cases were high and comparable in baseline and repeat groups, indicative of early stage. The baseline group contained a paucity of small-cell carcinomas, interpreted as a result of their rapid growth and clinical presentation, whereas typical carcinoids were only found in the baseline group

Conflict of interest statement

None declared.

Acknowledgement

Supported in part by an American Cancer Society grant.

References (21)

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1

See Appendix A.

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