An LDCT can detect lung (pulmonary) nodules—small and roundish or oval growths of tissues in the lung that appear white on an LDCT—with great accuracy. However, an LDCT does not indicate whether the nodule is cancerous or not. Pulmonary nodules are associated with infectious and inflammatory diseases as well as with lung cancer. As discussed earlier, most pulmonary nodules detected by LDCT are benign, that is, not cancerous.7,18

The first LDCT is known as the baseline screening. All LDCTS after this, known as follow-up screenings, are compared with the baseline screening to determine whether there is a reason to suspect lung cancer. The patient's medical history, the characteristics of the nodule, and how fast the nodule grows determine follow-up care. 

Based on whether a lung nodule is detected during the baseline screening, the NCCN® recommends the following:7

If no nodule is detected at this screening, the next LDCT should be in 12 months, with additional follow-ups every 12 months after that. The doctor will determine how many follow-up screenings the patient needs.

If one or more nodules are detected at the baseline screening, additional tests (including a CT and/or a PET/CT scan to get a clear view of the nodules and what is going on throughout the body) or a follow-up LDCT sooner than 12 months may be indicated. The type of follow-up recommended—and the timing of follow-up LDCTS—is based on several factors:

  • Size: The larger the nodule, the sooner the follow-up is likely to be. Nodules with a diameter of 5 mm or less are of the least concern.
  • Density: Density is how solid the nodule is, as determined by how well the X-rays from the LDCT pass through it. As discussed earlier, nodules that are solid and part-solid are of more concern for lung cancer than those that are nonsolid.
  • Location: Nodules that are located in the upper lobes of the lung are more likely to be cancerous.
  • Rate of growth: Nodules that grow faster are more likely to be cancerous. The growth rate of a nodule can be calculated by looking at the size of the nodule in follow-up scans.
  • Medical history: The healthcare team considers the presence of risk factors of lung cancer, including age and family history of lung cancer.

If at baseline or at a follow-up LDCT, a nodule's characteristics make it of high concern for lung cancer, either a biopsy or surgical removal of the nodule will be done to confirm whether the nodule is cancerous. If the patient does have lung cancer, further tests may be needed to determine the stage. For early-stage patients, treatment will be surgery or SBRT. For advanced-stage patients, treatment will begin, ideally after comprehensive biomarker testingAnalyzing DNA to look for gene mutations that can be treated with targeted therapy drugs and measuring the level of expression of the PD-L1 protein to determine the  likelihood of a good response to immunotherapy drugs takes place and a personalized treatment plan is developed.

For detailed information about the NCCN® guidelines for baseline and follow-up screenings, refer to NCCN® Guidelines for Patients: Lung Cancer Screening.

The American College of Radiology has developed a scoring system called Lung CT Screening Reporting & Data System® (Lung-RADS®) to standardize how results from CT scans are reported to reduce confusion in lung cancer screening CT interpretations and improve follow-up CT scans and care.20

The higher the score, the higher the probability of the nodule being cancerous and requiring follow-up. Not all LDCT results are reported in Lung-RADS® at this time.