SAN DIEGO – About 30% of nodules detected by CT screening fit the criteria for an indeterminate pulmonary nodule. Very few of those nodules represent cancer, and the question is, what do you recommend for those patients in terms of follow-up?
"We’re encountering more and more patients with lung nodules in the clinic, and with the advance of screening, it will become even more of a problem. The numbers are tremendous," Dr. Pierre P. Massion stated at the Joint Conference on the Molecular Origins of Lung Cancer, sponsored by the American Association for Cancer Research and the International Association for the Study of Lung Cancer.
Dr. Massion, the Ingram Professor of Cancer Research at Vanderbilt-Ingram Cancer Center in Nashville, Tenn., said it’s important to differentiate – early, accurately, and noninvasively – benign lesions from cancer. "There is a race for early diagnosis, because surgery is the best chance for cure ... but we also need to decrease the number of thoracotomies performed for benign disease."
Data from eight large trials of lung cancer screening examined the relationship between lesion size and the probability of lung cancer (Chest 2007;132[3 Suppl]:94S-107S). The probability of cancer was 0-1% for lesions less than 5 mm in diameter; 6%-28% for those 5-10 mm, 33%-60% for those 11-20 mm, and 64%-82% for those 21-30 mm.
"The bigger the nodule, the greater the probability of cancer. In fact, however, the number of large nodules is very small," Dr. Massion said. "The indeterminate ones are between 5 and 15 mm in diameter, and these are the ones we struggle with how best to handle." The probability of cancer from indeterminate pulmonary nodules ranges from 6% to 60%, which is a large range.
The shape of the nodule provides additional information, Dr. Massion said. Triangular shape abutting a fissure and central calcification are generally indicators of benign disease and typically do not require follow-up. Alternatively, solid, noncalcified spiculated nodules have a high likelihood of being cancer. Part solid nodules are "very worrisome," he said. "These are most likely to contain malignancy. Nonsolid lesions, also called ground-glass opacities, are troublesome and difficult to assess. They represent about a 20% probability of disease."
The rate of growth of small nodules over time "is probably one of the best imaging markers, [but] for small nodules such as those 5 mm in diameter, the volumetric analysis has a large coefficient of variance," he said.
Prediction models are important to the evaluation of lung nodules, yet even with existing tools "we’re wrong about 30% of the time," he said. The best three prediction models come from studies of patients at the Mayo Clinic (Arch. Intern. Med. 1997;157:849-55) and the Veterans Affairs department (Chest 2007;131:383-88), and from patients enrolled in the PLCO (Prostate, Lung, Colorectal, and Ovarian) Cancer Screening Trial (N. Engl. J. Med. 2013;368:728-36). These prediction models are now recommended for use on nodules greater than 8 mm in diameter in the ACCP 2013 guidelines for evaluation of lung nodules (Chest 2013;143[5 Suppl]:e93S-120S).
"We have no models for never-smokers, which is a huge problem in the community at the moment."
Dr. Massion predicted that serum biomarkers might "come to the rescue" for deciding which patients with indeterminate pulmonary nodules might need to go for a biopsy or resection and which can be carefully watched over time.
In a separate study of 62 lung nodules that integrated clinical, imaging, and protein biomarker findings, clinical information alone resulted in about 50% sensitivity for predicting disease, "which is not great," said Dr. Massion, who was the principal investigator (Cancer Epidemiol. Biomarkers Prev. 2012;21:786-92). The addition of CT imaging increased the area under the curve to about 61%. Adding biomarkers in the blood raised the bar to about 69%.
"It’s not a panacea, but we show a trend toward improvement of classification of these nodules, which is where I think this field is going – integrating information from the clinic, imaging, and the discriminatory power of biomarkers."
Dr. Massion said that he had no relevant financial conflicts to disclose.