Spiral CT Scanning Finds Very Early Lung Cancers

WASHINGTON—The Early Lung Cancer Action Program (ELCAP) has tested CT screening over the last decade and shown significant improvements in screening technology and substantially improved cure rates for cancers caught early.

At the lung cancer workshop Application of High Resolution CT Imaging Data to Lung Cancer Drug Development, sponsored by the Cancer Research and Prevention Foundation, Claudia I. Henschke, MD, PhD, presented the most recent results from ELCAP. She also provided a glimpse of imaging’s future, in which a CT image could give as much detail as a pathology image.

Every time a cell divides it’s called a doubling, said Dr. Henschke, professor of radiology, Weill Medical College of Cornell University. It takes about 40 doublings for lung cancer to reach the size that causes death from primary disease or metastasis, she said. A chest x-ray can reveal, at best, a 1-cm cancer, but typically only detects cancers that are 2 cm or larger. These are cancers that have already undergone about 30 to 32 doubling times. Helical or spiral CT, on the other hand, can detect 2-mm lesions. These lesions have undergone about 22 doubling times, which is still in the second half of the lifetime of the lung cancer, Dr. Henschke said. "The exciting potential of newer CT technologies that we’re working on is that we can finally get into the first half of the lifetime of that lung cancer and detect lesions that are 1 mm or smaller," she said.

ELCAP started in 1993 screening individuals at high risk for lung cancer—age 60 and older with a smoking history of a pack-a-day for 10 years. The international collaboration, involving 33 institutions, has accumulated 26,557 baseline scans, 19,742 repeat scans, and 373 cancers. They are collaborating with several European screening trials using the same system to pool data.

Of cancers detected to date in ELCAP, 80% were stage I disease, a stark contrast to usual care, in which only 5% to 15% of lung cancers are diagnosed at stage I. The 8-year case fatality rate for all stages of resected patients in ELCAP was 4%. In the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program, overall fatality is about 30%.

Throughout the past decade, Dr. Henschke’s team has been applying technological improvements to ELCAP. The latest advance is volume CT, which was developed based on research from Dr. Henschke’s group. In helical or spiral CT, the table moves around the patient as each row of detectors scans a part of the body. One row of detectors was improved to 2 rows, and soon to 64. The image is then built from 64 slices. With volume CT, instead of rows of detectors, one to four plates are in the scanner, allowing continuous slicing. "These plates are getting all of the information at one time, instead of one row at a time," she said. It increases resolution, and the patient is in the scanner for a very short time.

New scanners—used only in mice, but to be tested soon in humans—can obtain the whole volume of the lungs and improve resolution 30-fold over today’s best scanners, she said. The scans show bronchi, bony skeleton, and sternum. "It will make a big difference in what we can see," she said. Along with better imaging devices have come improved image processing, which will "provide more analytic tools to identify and measure abnormal areas ," Dr. Henschke said.

She pointed out the importance of distinguishing nodule consistency, noting which parts are solid, part solid, and nonsolid. Each grows at different rates, and her data show that part solid nodules are three times more likely to be malignant than solid and nonsolid nodules. Being able to view vascular structures in relation to the tumor helps as well.

Knowing these details about a tumor "may very well determine what our treatment options may be. Potentially, as we get more accuracy in volumetric tools, we may go directly to surgery or to some other treatment devised for these small cancers," she said.

Dr. Henschke ended with interesting findings in smoking cessation: 25% of smokers who go through her screening and receive smoking cessation information quit and are still not smoking at 1 year. "People used to call me up, especially if I went through their scan with them, and say ‘Every time I lit a cigarette, I thought of my CT scan,’" she said.