Spiral CT Scanning Finds Very Early Lung Cancers, ELCAP Data Show

WASHINGTON-The EarlyLung Cancer Action Program(ELCAP) has tested CT screening overthe last decade and shown significantimprovements in screening technologyand substantially improved curerates for cancers caught early.At the lung cancer workshop Applicationof High Resolution CT ImagingData to Lung Cancer Drug Development,sponsored by the CancerResearch and Prevention Foundation,Claudia I. Henschke, MD, PhD, presentedthe most recent results fromELCAP. She also provided a glimpseof imaging of the future, in which aCT image could give as much detailas a pathology image.

Every time a cell divides, it is calleda doubling, said Dr. Henschke, professorof radiology, Weill Medical Collegeof Cornell University. It takes about 40 doublings for lung cancer to reachthe size that causes death from primarydisease or metastasis, she said. Chestx-ray can reveal, at best, a 1-cm cancer,but typically only detects cancers thatare 2 cm or larger. These are cancersthat have already undergone about 30to 32 doubling times. Helical or spiralCT, on the other hand, can detect2-mm lesions. These lesions have undergoneabout 22 doubling times, whichis still in the second half of the lifetimeof the lung cancer, Dr. Henschke said."The exciting potential of newer CTtechnologies that we're working on isthat we can finally get into the first halfof the lifetime of that lung cancer anddetect lesions that are 1 mm or smaller,"she said.ELCAP started in 1993 screeningindividuals at high risk for lung cancer-age 60 and older with a smokinghistory of a pack-a-day for 10 years.The international collaboration, involving33 institutions, has accumulated26,557 baseline scans, 19,742 repeatscans, and 373 cancers. They arecollaborating with several Europeanscreening trials using the same systemto pool data.Of cancers detected to date in ELCAP, 80% were stage I disease, astark contrast to usual care, in whichonly 5% to 15% of lung cancers arediagnosed at stage I. The 8-year casefatality rate for all stages of resectedpatients in ELCAP was 4%. In theNational Cancer Institute's Surveillance,Epidemiology, and End Results(SEER) program, overall fatality isabout 30%.Throughout the past decade, Dr.Henschke's team has been applyingtechnological improvements toELCAP. The latest advance is volumeCT, which was developed based onresearch from Dr. Henschke's group.In helical or spiral CT, the table movesaround the patient as each row of detectorsscans a part of the body. Onerow of detectors was improved to 2rows, and soon to 64. The image isthen built from 64 slices. With volumeCT, instead of rows of detectors,one to four plates are in the scanner,allowing continuous slicing. "Theseplates are getting all of the informationat one time, instead of one row ata time," she said. It increases resolution,and the patient is in the scannerfor a very short time.New scanners-used only in mice,but to be tested soon in humans-can obtain the whole volume of thelungs and improve resolution 30-foldover today's best scanners, she said.The scans show bronchi, bony skeleton,and sternum. "It will make a bigdifference in what we can see," shesaid. Along with better imaging deviceshave come improved image processing,which will "provide more analytictools to identify and measureabnormal areas ," Dr. Henschke said.She pointed out the importance ofdistinguishing nodule consistency,noting which parts are solid, part solid,and nonsolid. Each grows at differentrates, and her data show thatpart solid nodules are three timesmore likely to be malignant than solidand nonsolid nodules. Being ableto view vascular structures in relationto the tumor helps as well.Knowing these details about a tumor"may very well determine whatour treatment options may be. Potentially,as we get more accuracy in volumetrictools, we may go directly tosurgery or to some other treatment devisedfor these small cancers," she said.Dr. Henschke ended with interestingfindings in smoking cessation:25% of smokers who go through herscreening and receive smoking cessationinformation quit and are still notsmoking at 1 year. "People used tocall me up, especially if I went throughtheir scan with them, and say 'Everytime I lit a cigarette, I thought of myCT scan," she said.