NEW YORKTwo important developments are bringing about a reappraisal of major institutional policy recommendations against lung cancer screening: (1) The amassing of compelling evidence that resection of early lung cancer has a major impact on survival and (2) the emergence of new techniques allowing earlier disease detection.
The reappraisal was clear from presentations at the First International Conference on Screening for Lung Cancer, convened among experts in the field, and was manifested in the formation of a new group called ICScreen (International Collaboration to Screen for Lung Cancer).
Noting that lung cancer kills more individuals than breast, colon, cervix, and prostate cancer combined, the consensus statement issued postconference provided a rationale for a change of strategy.
Recent scientific advances create an extraordinary potential to develop a lung cancer screening program that would prevent untimely deaths of vast numbers of current and former smokers who remain at high risk despite smoking cessation, the statement said. An estimated 160,000 lung cancer deaths will occur this year in the United States.
The criteria for an acceptable screening test are that it be simple, inexpensive, noninvasive, potentially widely available, and accurate. The consensus statement from the conference suggests that, for lung cancer screening, these criteria are met by the combined use of spiral computed tomography (CT) and automated airway cell marker analysis.
While CT scanning detects peripheral tumors, airway cell marker analysis detects positive cells in the sputum and has good sensitivity for picking up squamous-cell and small-cell cancers.
Confidence in these modalities rests on international experience involving more than 20,000 spiral CT scans and 9,000 airway cell marker analyses. Research from Japan, where experience with spiral CT scan screening for lung cancer is most extensive, suggests that the technique can aid in early detection and save lives.
Tomotaka Sobue, MD, MPH, National Cancer Center Research Institute, Tokyo, Japan, compared data from lung cancer screening collected at two distinct time points in a cohort consisting primarily of smokers over the age of 50. Screening from 1975 to 1993 was by chest x-ray plus sputum cytology twice yearly, and screening from 1993 to 1998 was with low-dose spiral CT scan and sputum cytology twice yearly.
Nearly 26,000 exams were conducted in the first period among 2,529 subjects; 43 lung cancers were detected, Dr. Sobue said. In the second period, 10,000 exams among 1,678 subjects detected 36 lung cancer cases. The crude detection rates, Dr. Sobue noted, were 0.16% in the first period and 0.37% in the second.
While cautioning that the follow-up period is insufficient, Dr. Sobue reported that 5-year survival is higher among individuals whose cancers were detected through spiral CT scanning (82.6% vs 48.8% for the first period). CT alone detected 90% of the cancers found in the second period, and survival was nearly 90% in that group. These figures indicate that CT-detected lung cancer cases are highly curable, Dr. Sobue said.
Dr. Sobue acknowledged that biases leading to overdiagnosis are a possibility, but noted that analysis of current retrospective data cannot clearly separate out such biases. Importantly, he estimates that the length of the preclinical detectable phase of lung cancer for CT screening is more than 5 years.
Screening is of value, the conference attendees agreed, only when it is linked with appropriate diagnostic interventions and treatment. They concluded that further evaluations of lung cancer screening should be conducted within the framework of an overall research program leading to a standardization of diagnostic evaluations and treatments, to minimize unnecessary diagnostics, invasive procedures, and surgery.
Further research is needed to determine more precisely which populations should be screened and how often, and to identify noninvasive diagnostic algorithms for abnormal screens, as well as treatment algorithms.