Chest X-Ray Yearly Screening Found Not to Reduce Rate of Lung Cancer Deaths

“Lung cancer is the leading cause of cancer death in the United States and worldwide. Screening for lung cancer has long been studied as an approach to reducing the burden of lung cancer,” according to background information in the article. “The effect on mortality of screening for lung cancer with modern chest radiographs is unknown.”

Martin M. Oken, MD, from the University of Minnesota (Minneapolis, MN, USA), and colleagues assessed the effect on mortality of screening for lung cancer using radiographs in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. This randomized controlled trial involved 154,901 participants, ages 55 through 74 years, of whom 77,445 were assigned to annual screenings and 77,456 to usual care, at one of 10 screening centers across the United States, between November 1993 and July 2001. The groups were similar: approximately half were women (50.5%); about 45% were never smokers, 42% former smokers, and 10% current smokers.

Study participants in the intervention group were offered an annual chest radiograph for four years. Diagnostic follow-up of positive screening results was determined by participants and their healthcare practitioners. Participants in the usual care group were not offered chest radiograph screening and they received their usual medical care. All diagnosed cancers, deaths, and causes of death were established through the earlier of 13 years of follow-up or until December 31, 2009.

Adherence to screening was 86.6% at the start of the trial, decreasing to 79% by year three. The overall adherence rate was 83.5%, and 91.2% of participants had undergone at least one radiographic screening. In the usual care group, the contamination rate (i.e., rate of chest X-ray screening) during the screening phase of the trial was estimated at 11%.

During the entire 13-year study period, there were 1,696 lung cancers detected in the intervention group and 1,620 lung cancers in the usual care group. Of participants detected with lung cancer during the follow-up, stage and histology was similar by group, with about 41% being adenocarcinoma, 20% squamous cell carcinoma, 14% small cell carcinoma, 5% large cell carcinoma, and 20% other non-small-cell lung cancer.

Concerning the effect on mortality, the researchers found that yearly chest radiographic screening for up to four years did not significantly decrease lung cancer mortality compared with usual care: for the total 13-year follow-up period, 1,213 lung cancer deaths were observed in the intervention group versus 1,230 in the usual care group.

“The randomized groups in PLCO were comparable at baseline, there was relatively high screening adherence in the intervention group and low contamination in the usual care group, and the treatment distributions across the groups were similar. Therefore, these findings provide good evidence that there is not a substantial lung cancer mortality benefit from lung cancer screening with four annual chest radiographs,” the authors wrote.

In an accompanying editorial, Harold C. Sox, MD, from Dartmouth Medical School (West Lebanon, NH, USA) commented on the findings of this study, “The PLCO lung cancer study result provides convincing evidence that lung cancer screening with chest radiography is not effective. The study is important for putting this question to rest and providing strong empirical grounds for comparing low-dose computed tomography to a real-world alternative: usual care. The [US] National Lung Screening Trial showed convincingly that early detection can lower the risk of death from lung cancer, a big step forward. How that evidence will translate into policy and practice will depend on analyses still to be completed. The PLCO trial is another important step, confirming expectations rather than setting new ones.”

Related Links:
University of Minnesota
Dartmouth Medical School