In a controversial move, the American College of Chest Physicians has formally recommended against the use of low-dose helical CT scanning for general lung cancer screening, even in high-risk populations, except in the context of clinical trials.
The ACCP also recommended against the use of serial chest radiographs and sputum cytologic evaluation to screen for the presence of lung cancer.
“The evidence isn't available to show that low-dose CT screening provides a mortality benefit,” Dr. W. Michael Alberts said in an interview. Dr. Alberts, the chief medical officer of the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Fla., chaired the ACCP committee that developed the guidelines. “Because there's a very real potential for harm, it's going to be important to prove or show a mortality benefit prior to recommending screening with a low-dose CT scan.”
The second edition of the college's “Diagnosis and Management of Lung Cancer” includes 260 guidelines, three of which involve lung cancer screening. It was published as a supplement to the September 2007 issue of the journal Chest (2007;132[suppl.]:1S–422S). This edition updates the original version of the guidelines, published in January 2003.
The screening guidelines were developed by a subcommittee headed by Dr. Peter B. Bach of the Memorial Sloan-Kettering Cancer Center, New York. Although acknowledging that low-dose CT scanning remains the most promising of the lung cancer screening techniques, the guideline authors maintain that—even though the existing data do suggest that low-dose CT increases the rate of detection of early-stage lung cancers—such CT screening fails to reduce the number of late-stage lung cancers or the risk of dying from lung cancer. They suggest that this may be because many of the additional cancers detected are small, indolent cancers, which leads to unnecessary invasive procedures that carry a cost in morbidity and mortality.
The subcommittee's analysis includes a theoretical model of the time it takes for a given nodule to double in size. They estimated that the doubling time of lung tumors resulting in deaths is approximately 40–70 days, whereas research shows that the doubling time of early cancers identified by CT screening ranges from 149 to 813 days.
“As best I know, this is the first time that anyone has tried to make a public health policy statement against screening based upon theoretical considerations of nodule doubling time,” said Dr. James L. Mulshine of Rush University Medical Center, Chicago, in an interview. “This is a totally unvalidated tool, and really not the grist for evidence-based analysis of the screening service.”
“The recommendations weren't based on that at all,” Dr. Bach responded in an interview. Instead, he said, the model was intended to provide one possible explanation for the fact that studies have so far failed to demonstrate that screening results in demonstrable improvements in mortality.
Dr. Mulshine said that some studies were omitted from the analysis unfairly, and that the guideline authors interpreted other studies selectively. He is on the board of directors of the Lung Cancer Alliance (www.lungcanceralliance.org
Dr. Mulshine acknowledged the lack of persuasive evidence from double-blind studies showing reduced mortality related to lung cancer screening. One such study may be completed as early as 2009, but possibly not until 2011. Data from another study won't be available for another 2 years or so after that.
“We all hope that the randomized, controlled trials will show a mortality benefit,” Dr. Alberts said. “We'd like to have that outcome, at which time maybe low-dose CT scanning should be recommended. But at this time, the evidence is not available, and there is potential evidence that it may be harmful. As a result, we can't in all good conscience recommend CT scanning at this point.”
But Dr. Mulshine noted that while waiting for the results of those randomized trials, 160,000 Americans die every year from lung cancer, in part because most lung cancer is not diagnosed until it's stage III or IV. And he pointed to data showing that morbidity and mortality from diagnostic procedures conducted as a result of screening are extraordinarily low in “centers of excellence.” Furthermore, the last 5 years have seen a significant improvement in noninvasive procedures, improvements that are likely to continue if more research is done in this area.
But for Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, “the issue isn't diagnostic procedures. It's the morbidity and mortality from subsequent surgery that concerns me.” ACS does not recommend routine CT screening for lung cancer at this time.” However, “understanding that some people will nonetheless want to proceed with screening, they should have a careful discussion with their doctor regarding the potential risks that could result.”