Lung Cancer Risk in Suspicious Lung Nodules With Negative Positron Emission Tomography

Lung CT Screening Reporting and Data System (LungRADS) Category 4 represents lung nodules with the highest likelihood of cancer. For LungRADS-4 lesions, if positron emission tomography (PET) is negative, no uniform guideline currently exists on subsequent follow-up, particularly whether the surveillance interval can be extended. We sought to investigate the incidence of cancer, our surveillance practice, and any clinical factors associated with cancer in this patient subset.

We retrospectively stratified LungRADS-4 patients screened at our institution from March 2015 to February 2019 into subgroups: PET positive, PET negative, and no PET performed. PET negativity was defined as the absence of a radiologist's suspicion or a maximum standardized uptake value at or below the mediastinal value.

Of the 191 LungRADS-4 patients identified, 67 (35.1%) met the criteria for PET negativity. Cancer was diagnosed in 28.8% of the entire cohort (55/191), 77.8% of the PET-positive subgroup (35/45), 22.4% of the PET-negative subgroup (15/67), and 6.3% of the no PET subgroup (5/79). The most common follow-up modality after a negative PET was a computed tomography (47/67, 70.1%), with a median interval of 3.1 months. Clinical variables including nodule location/size, chronic obstructive pulmonary disease, family history of lung cancer, pack-years, and number of years quit in former smokers were not significantly associated with greater cancer risk among the PET-negative subgroup.

For LungRADS-4/PET-negative lesions the cancer risk remained high despite a lack of activity on PET. As such we believe the current surveillance practice of continuing to follow LungRADS-4/PET-negative patients as LungRADS-4 patients is appropriate.