The following is a summary of “Volume Doubling Time of Pulmonary Carcinoid Tumors Measured by Computed Tomography,” published in the November 2022 issue of Clinical Lung Cancer by Russ, et al.

About 2% of all cases of lung cancer are diagnosed as pulmonary carcinoid tumors (PCTs), a rare neuroendocrine lung neoplasm. It is subdivided into 2 groups: low-grade (typical) and intermediate-grade (atypical) forms that are confined. Clinically, PCT is considered a slow-growing malignancy, although a small number of investigations using computed tomography (CT) has only established the true growth rate over time. Therefore, researchers set out to calculate the time required for PCTs observed using CT to double in volume. Investigators looked back at all PCTs seen by the clinic between 2006 and 2020 and analyzed the data. The size of each nodule was determined by consulting either a radiological report or an archival image. For PCTs followed by subsequent CT scans during radiographic surveillance, the volume doubling time was determined using the Schwartz formula.

According to the Fleischner Society, tumors were only regarded to have shown definitive growth by CT when the interval change in tumor diameter was larger than or equivalent to 2 mm. About 13 representative PCTs had a median volume doubling time of 977 days (or 2.7 years). The median doubling time for the 5 atypical PCTs that were tracked throughout time was 327 days (or 0.9 years).

When compared to other types of lung cancer, the growth rate of a typical pulmonary carcinoid is extremely modest. Too few patients were included in the study of atypical pulmonary carcinoid to draw any firm findings. Clinicians adhering to the existing nodule monitoring recommendations may incorrectly diagnose incidentally found typical carcinoids as benign non-growing lesions in low-risk patients if they are observed for less than 2 years.