Potential lung cancers that show up as nonsolid nodules (NSNs) are innocuous enough that they can be appropriately managed by annual low-dose CT scans in lieu of immediate biopsy or treatment, according to a study published July 5 in Radiology.

Rowena Yip, MPH, Icahn School of Medicine at Mount Sinai, and colleagues arrived at this conclusion after reviewing all cases of lung cancer manifesting as NSNs, which are so called because they are translucent upon visual inspection, in the National Lung Screening Trial (NLST).

The researchers then narrowed the field to NSN-positive patients whose lung cancer proved fatal.

Of 26,722 patients who had one or more NSNs, 48 died of lung cancer. Of these, 21 had no NSNs in the lobe with the cancer.

This left 27 patients, and their CT scans were reviewed by four radiologists and placed into two groups for review.

Group A (n = 12) were cases of lung cancer as the cause of death because of adenocarcinoma. Group B (n = 15) were cases of lung cancer as the cause of death because of other cell types.

The team found that six of the 12 patients in group A had no NSNs in the cancerous lobe. The remaining six patients had a dominant solid or part-solid nodule in the lobe that rapidly grew in four patients. This was multifocal in one patient, and another patient had a growing NSN with no diagnosis of cancer until three years later.

Five of the 15 patients in group B had no NSNs—and, for the remaining 10 patients, lung cancer as the cause of death was not because of NSNs.

“Among the 27 lung cancer deaths with an NSN that manifested in the same lobe as the cancer, cause of death was most likely because of another dominant solid or part-solid nodule,” Yip et al. write.

“It seems unlikely that patients with lung cancer as the cause of death occurred with solitary or dominant NSN as long as annual follow-up was performed,” the authors write in their conclusion. “This lends further support that lung cancers that manifest as NSNs have an indolent course and can be managed with annual follow-up.”

A press release from Radiology publisher RSNA points out that NSNs have been turning up in findings more frequently ever since the American Cancer Society recommended low-dose CT for high-risk smokers in 2013.

CMS began reimbursing for the tests the next year, and screening programs have evidently been drawing more patients.

“When you biopsy a nonsolid nodule, it’s usually pre-malignant, noninvasive or due to some other cause like infection or fibrosis,” says study co-author Claudia Henschke, MD, PhD, in the release.

“The causes of death in this group were likely due to another solid or part-solid nodule in the same lobe of the lung,” adds Yip. “In the one death related to a growing nonsolid nodule, the time from prior CT to diagnosis was greater than three years.”

In their discussion section, the authors note that their new work validates the previous International Early Lung Cancer Action Program study, which similarly looked at lung cancers manifesting as NSNs. That study showed a long-term, lung-cancer-specific survival rate of 100 percent.