Growth rates of lung cancers found by annual rounds of computed tomography (CT) screening are important for determining the usefulness and frequency of screening, as well as for determining the treatment.
"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 Doctor Claudia I. Henschke. "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 diagnosed in clinical practice in the absence of screening. Also, the frequencies of small-cell carcinoma and adenocarcinoma among all lung cancers have been reported to be approximately 20 per cent and 50 per cent, respectively, in the absence of screening. In repeat rounds of CT screening, these frequencies were nearly identical (19 per cent and 50 per cent).
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," Henschke said. The first, or baseline, round of screening for any cancer detects a higher proportion of slower-growing cancers than those detected in clinical practice, she noted. The subsequent, repeat rounds of screening, however, reflect what is found in clinical practice.
The study found that there is a difference in the growth rates of cancers 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," 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 prior screening seven to 18 months earlier. Of the 111 cancers identified, 88 were clinical Stage I. The investigators then analyzed volume doubling time and cell-type distribution.
The results showed that the median volume doubling time was 98 days. Most of the cancers, 99 of the 111, manifested as solid nodules, while only 12 of the cancers manifested as sub-solid nodules. Solid nodule cancers had significantly faster volume doubling times than sub-solid nodule cancers. According to Henschke, identifying the volume doubling times for specific lesion types may lead to more tailored treatment for the patient.
MEDICA.de; Source: International Early Lung Cancer Action Program (I-ELCAP)