Lung Cancers Diagnosed at Annual CT Screening: Volume Doubling Times

Published Online:https://doi.org/10.1148/radiol.12102489

The distribution of volume doubling times of cancers diagnosed in annual rounds of CT screening is not significantly different from that previously reported in an earlier study for all cancers (P = .51) or for non–small cell cancers only (P = .69).

Purpose

To empirically address the distribution of the volume doubling time (VDT) of lung cancers diagnosed in repeat annual rounds of computed tomographic (CT) screening in the International Early Lung Cancer Action Program (I-ELCAP), first and foremost with respect to rates of tumor growth but also in terms of cell types.

Materials and Methods

All CT screenings in I-ELCAP from 1993 to 2009 were performed according to HIPAA-compliant protocols approved by the institutional review boards of the collaborating institutions. All instances of first diagnosis of primary lung cancer after a negative screening result 7–18 months earlier were identified, with symptom-prompted diagnoses included. Lesion diameter was calculated by using the measured length and width of each cancer at the time when the nodule was first identified for further work-up and at the time of the most recent prior screening, 7–18 months earlier. The length and width were measured a second time for each cancer, and the geometric mean of the two calculated diameters was used to calculate the VDT. The χ2 statistic was used to compare the VDT distributions.

Results

The median VDT for 111 cancers was 98 days (interquartile range, 108). For 56 (50%) cancers it was less than 100 days, and for three (3%) cancers it was more than 400 days. Adenocarcinoma was the most frequent cell type (50%), followed by squamous cell carcinoma (19%), small cell carcinoma (19%), and others (12%). Lung cancers manifesting as subsolid nodules had significantly longer VDTs than those manifesting as solid nodules (P < .0001).

Conclusion

Lung cancers diagnosed in annual repeat rounds of CT screening, as manifest by the VDT and cell-type distributions, are similar to those diagnosed in the absence of screening.

© RSNA, 2012

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Article History

Received February 10, 2011; revision requested March 30; revision received December 6; accepted December 13; final version accepted January 13, 2012.
Published online: May 2012
Published in print: May 2012