Lung Tumor Growth Rates Revealed by CT Screening

Growth rates of lung cancers identified by yearly rounds of computed tomography (CT) screening are vital for determining the usefulness and frequency of screening, as well as for determining the treatment. According to a recent report, lung cancers diagnosed in annual repeat rounds of CT screening are comparable--both in volume doubling time and cell-type distribution--to those found in clinical practice.

The International Early Lung Cancer Action Program (I-ELCAP; Temple, AZ, USA) report was published online March 29, 2012, in the journal Radiology. “There was concern that cancers diagnosed in the screening context were somehow different than cancers found in routine practice, that they were not aggressive,” said I-ELCAP principal investigator Claudia I. Henschke, MD, PhD, and professor of radiology at Mount Sinai School of Medicine (New York, NY, USA). “We demonstrate here that they are quite similar.”

The researchers reported that growth rates found in cancers detected in repeat rounds of annual CT screening are not significantly different from growth rates reported for cancers detected in clinical practice in the absence of screening. In addition, the frequencies of small-cell carcinoma and adenocarcinoma among all lung cancers have been reported to be approximately 20% and 50%, respectively, in the absence of screening. In repeat rounds of CT screening, these frequencies were nearly identical (19% and 50%).

Lung cancer is the leading cause of cancer death among men and women. The American Cancer Society estimates that in 2012, about 226,160 new cases of lung cancer will be diagnosed in the United States alone and 160,340 people will die from the disease.

CT screening has been found effective in detecting lung cancer at its earliest, most curable stage. “This study shows that the cell types of cancer diagnosed in annual rounds of screening, as well as their growth rates, are quite similar to those that are found in clinical practice where it is well understood that lung cancer is highly lethal,” Dr. Henschke said. The first, or baseline, round of screening for any cancer identifies a higher degree of slower-growing tumors than those detected in clinical practice, she noted. The subsequent, repeat rounds of screening, however, mirror what is found in clinical practice.

The study’s findings showed that there is a difference in the growth rates of tumors in solid and sub-solid lesions and that the sub-solid ones tend to be less aggressive than solid ones. “This suggests that a less aggressive approach is indicated for both diagnosis and treatment of sub-solid lesions,” Dr. Henschke said.

The researchers reviewed results from the I-ELCAP database for 1993 to 2009, consisting of men and women at risk for lung cancer who underwent annual repeat rounds of CT screening. The research team identified 111 instances of first primary lung cancer diagnosed either through screening or between rounds after a negative result of the earlier screening seven to 18 months earlier. Of the 111 tumors identified, 88 were clinical stage I. The investigators then assessed volume doubling time and cell-type distribution.

The findings revealed that the median volume doubling time was 98 days. Most of the tumors, 99 of the 111, manifested as solid nodules, whereas only 12 of the tumors manifested as subsolid nodules. Solid nodule cancers had considerably faster volume doubling times than subsolid nodule cancers. According to Dr. Henschke, identifying the volume doubling times for specific lesion types may lead to more tailored treatment for the patient.

Volume doubling times for lung tumors detected in clinical practice in the absence of screening have been reported to range from 20 to 360 days. A recent study, based on a systematic medical literature review, reported a mean volume doubling time of 135 days for non-small-cell lung cancers diagnosed in the absence of screening.

Dr. Henschke recommended that individuals at high risk for lung cancer talk with their physician to discuss the benefits and risks of screening so as to make an informed decision about enrolling in a screening program.

Related Links:
International Early Lung Cancer Action Program
Mount Sinai School of Medicine