Sputum Cytology Complements CT in Lung Cancer Screening Effort

NEW YORK—The development of computers and diagnostic platforms is facilitating mass screening for lung cancer not only with helical CT but also with sputum cytology, according to Melvyn S. Tockman, MD, PhD, professor of medicine and director, Program in Molecular Screening, H. Lee Moffitt Cancer Center & Research Institute, University of South Florida, Tampa.

Dr. Tockman sees detection of sputum molecular markers as being complementary to CT findings. "Compared to helical CT, molecular airway markers detect lung cancers at a complementary stage, clonal vs invasive, and at complementary locations, central vs peripheral," he said at the 3^rd International Conference on Screening for Lung Cancer.

Sputum studies, Dr. Tockman added, also yield cell types not usually seen in lesions detected on CT.

The Moffitt Cohort Study, he said, is using both sputum cytology and helical CT lung scans. "The hypothesis is that we will increase the percentage of stage I detected cancer threefold, from the standard Florida cancer data system of 20% in stage I to 60%," he said.

For the clonal phase of cancer development, Dr. Tockman said, the researchers will look at sputum specimens. "We’re going to investigate transformed premalignant cells and clonal expansions at their origin on the epithelial surface. We’re going to sample that transformation and progression through exfoliated cells prior to clinical malignancy."

In contrast, he said, for invasive lesions or lesions large enough to already have their own blood supply, "we’ll take a look at helical CT."

Sputum specimens are being collected annually from 1,100 individuals in the Moffitt study and examined for morphology and other markers of preneoplasia, including upregulated gene expression of the hnRNPA2/B1 protein. Eligibility criteria include age 45 years or older, a history of 30 pack-years of smoking, and pulmonary obstruction as evidenced by an FEV1 :FVC ratio of 70% or less.

Preliminary findings, Dr. Tockman reported, include a prevalence (positive scans) of 34%. "We’re seeing somewhat more cases of cancer than expected," he said. The incidence was 1.9%—compared with 1.1% in the Early Lung Cancer Action Project (ELCAP) study—with 25% being stage I. Three persons had stage IV cancer when screened.

Noting that 80% of the cancers detected in ELCAP were stage I, Dr. Tockman said, "I suspect that much of the difference may be due to the fact that this younger population has more aggressive tumors." ELCAP required subjects to be at least 60 years of age.

Since nearly all smokers start the habit before age 20, he said, cancers detected after age 60 may grow more slowly than those occurring in younger persons.