Spiral CT Screening Detects Lung Cancer, but at What Cost?

Laurie Barclay, MD

July 26, 2002

July 29, 2002 -- A study and several commentaries in the July issue of Chest fan the flames of controversy over the potential benefits, and harms, of lung cancer screening using spiral computed tomography (CT).

"Low-dose spiral CT seems to be a promising method for screening early lung cancer as a part of annual health examinations," write Takeshi Nawa and colleagues from the Hitachi Health Care Center in Ibaraki, Japan. "The sensitivity of the baseline screening was very high, but decreased markedly at the repeat screening one year later. This casts a serious doubt about whether early lung cancer detection should be performed by routine yearly CT screening."

Their screening program using low-dose spiral CT in 7,956 individuals detected 2,865 noncalcified solitary pulmonary nodules at least 8 mm in diameter. Patients with these lesions had detailed CT scanning approximately one month later. Histology confirmed the diagnosis of 41 lung cancers, including 35 stage I tumors, in 40 patients, of whom only 17 were smokers. Detection rate was higher in women than in men.

"Female and nonsmoking subjects should be included in the baseline screening," the authors write. "However, for yearly repeat screening, the participants may be selected on the basis of gender, smoking history, and results at the baseline screening."

Jerome M. Reich, MD, FCCP, in private practice in Portland, Oregon, provides a detailed hypothesis and supporting data suggesting that annual lung cancer screening is not yet ready for routine clinical use. In many trials, mortality rates have not improved even if survival has.

"Increased survival, with no change in mortality rate, is most often attributable to lead-time bias, in which improvements in ascertainment permit diagnosis at an earlier point in time without affecting longevity (outcome)," he writes. "Thus, earlier diagnosis of a highly lethal and untreatable neoplastic disorder would improve survival without affecting mortality rate. Theoretical and experimental evidence indicates that earlier detection will increase overdiagnosis and will fail to substantially influence mortality rate. Tumor biology (phenotype) is determinative."

Further caveats in estimating the average duration of life saved by early detection include advanced age and heavy smoking history of study participants, putting them at high risk for heart and lung disability and death, and the presence of occult metastases in about half of apparently curable lung cancer.

"It would be unforgivable if a prematurely established lung cancer-screening program resulted in more harm than benefit," agrees Pamela Marcus, MS, PhD, from the National Cancer Institute in Bethesda, Maryland. "Ignoring the financial costs and the strains on the health-care system, it seems, from an ethical perspective, that it would be acceptable to implement mass screening programs at this point in time only if lung cancer screening were, at worst, innocuous. What must be acknowledged is that no mass cancer screening program is ever innocuous; even in the presence of a benefit, there is a guarantee of harm." She describes potentially harmful effects ranging from discomfort, minor inconvenience and wasted healthcare dollars to premature deaths from thoracotomy complications.

On the other hand, Frederic W. Grannis Jr., MD, FCCP, from City of Hope National Medical Center in Duarte, California, argues that "Reich's theory, model, and conclusions are based entirely on indirect and circumstantial evidence." Grannis cites two clinical series documenting very low survival in early stage lung cancer patients who are not treated after diagnosis by screening.

"Because there are so many billions of dollars involved in the implementation of [lung cancer] screening, it is important to consider whether there are any potential conflicts of interest that might compromise unbiased debate," he writes, noting possible financial benefits of screening to radiologists and surgeons but increased up-front costs for governments, medical insurance companies, and managed care organizations. In a recent lawsuit, the tobacco industry "convinced jurors that lung cancer screening was ineffective and dangerous," thereby avoiding payment for CT and pulmonary function screening in 250,000 smokers and ex-smokers in West Virginia.

"While Reich is correct in insisting that there are important pitfalls in screening, it is important to put lung cancer screening into a 21st century perspective," he writes, mandating design and implementation of better controlled trials in lung cancer screening. "There is definitely room for a reasonable difference of opinion over which type of study is superior. What is not acceptable is unwarranted overemphasis on highly theoretical risks while turning a blind eye on the very real carnage caused by lung cancer. What is not acceptable is further pointless delay in implementing life-saving early detection strategies."

Chest. 2002;122(1):1-3, 15-20, 329-337

 

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