Longer lung-cancer-screening intervals may sometimes be OK

By Will Boggs MD

NEW YORK (Reuters Health) - 27/5/2019

"In our study population, we identified factors observable on CT that provided additional information to estimate an individual's future risk of being diagnosed with lung cancer," Dr. Hilary A. Robbins from International Agency for Research on Cancer, in Lyon, France, and Dr. Hormuzd A. Katki from the National Cancer Institute, in Rockville, Maryland, told Reuters Health in a joint email.

"If replicated, the addition of these factors could help inform long-term management and appropriate screening intervals for smokers undergoing lung cancer screening," they said. Several studies have shown that lung-cancer-screen-negative individuals have reduced lung-cancer risk over subsequent screens, but not all screen-negatives have low enough risk to justify lengthening screening intervals.

Dr. Robbins, Dr. Katki and colleagues previously developed the Lung Cancer Risk Assessment Tool (LCRAT) to predict pre-screening lung-cancer risk. In the current study, they developed and tested a simple model, LCRAT+CT, that predicts short-term lung-cancer risk following a negative CT.

Among more than 23,000 NLST participants with at least one negative CT, 43 interval cancers arose after some 56,900 negative screens (for a mean risk of 0.08%); 138 next-screen cancers were detected after some 35,500 negative screens (for a mean risk of 0.4%).

The median next-screen risk was reduced from 0.3% to 0.2% among the 70% of screen-negative participants with neither emphysema nor consolidation on their negative CT, whereas the risk increased 1.6-fold among the 30% with CT-detected emphysema and 5-fold among the 0.6% with CT-detected consolidation, the researchers reported in the Journal of the National Cancer Institute, online April 12.

Next-screen risk was below 0.3% for 57.8% of screen-negative participants, in whom 23.9% of next-screen cancers were detected and 49.8% of the next-screen false-positives occurred. Therefore, lengthening the screening interval for these screen-negative participants might have avoided 50% of the false-positives but could also have delayed diagnosis for 24% of the cancers.

Of these cancers, 55% were stage 1, and these might have become incurable if the screening interval had been extended to two years (delaying diagnosis by one year). "In the future, LCRAT+CT could allow clinicians to continually update individual lung cancer risk using smoking history, other lung-cancer risk factors, and CT screen results," Dr. Robbins and Dr. Katki said. "However, further research is necessary before longer (e.g., 2-year) intervals can be incorporated into recommendations. If and when this is considered, our findings suggest that basing the length of intervals on individual risk may be an efficient approach."

"The best way to reduce risk for lung cancer and other smoking-related diseases is to quit smoking," they said. "Individuals who are ready to quit can visit https://smokefree.gov/ for more information."

"Current guidelines recommend annual lung screening for eligible current or former smokers (age 55-80, at least 30 pack-years, no more than 15 quit-years)," they added. "In the United States, most people who are eligible have not started lung-cancer screening with CT. The most important practical problem in preventing lung-cancer death through screening is recruiting eligible participants."

Dr. David S. Gierada from Washington University School of Medicine in St. Louis, Missouri, who studies lung-cancer screening, told Reuters Health by email, "The USPSTF recommendation of an annual screening interval for the eligible population overall was also based on modeling of NLST data. Still I was somewhat surprised that the subgroup in the lowest risk threshold with the lowest delayed diagnosis rate in the current study wasn't larger."

"While a matter of individual preference, as noted by the authors, one could reasonably conclude that only the lowest risk threshold would have a delayed-diagnosis rate low enough to justify lengthening the screening interval," he said.

"As the authors emphasize, their findings may help guidelines committees decide whether lengthening the screening interval may be appropriate for some individuals," Dr. Gierada said. "However, the standard of care currently remains that lung-cancer screening should be performed annually in eligible individuals."

SOURCE: https://bit.ly/2IP0wPv

J Natl Cancer Inst 2019

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