Finnish investigators recently reported that the survival rates of patients whose lung cancer was found during screening with a single chest radiograph were significantly higher than survival rates in patients whose cancer was detected through “the ordinary health care system.” Their study was published in Chest, the journal of the American College of Chest Physicians (ACCP).
Study Design
In this study, 290,000 men underwent screening for cancer as part of a large cancer prevention study in southwestern Finland. Those who were found to have cancer were excluded from the study.
A total of 93 of the excluded participants were found to have lung cancer as a result of a single chest radiograph and became the “screened” or study group in an investigation headed by Dr. Elja-Riitta Salomaa of Turku University Hospital in Preitila, Finland. These men were compared with 239 men in the same age range whose lung cancer was detected in what researchers described as the ordinary health care system or “other cases.” These men were identified through the local hospital discharge register. Of the 239 patients, 74 had their cancer detected by chest radiographs taken to control diseases other than lung cancer.
The premise of the study was that lung cancer prognosis is better if the diagnosis is made early when the disease is still localized and is curable with radical surgery.
Differences Between Screened and “Other Cases” Groups
There were differences between the “screened” and the “other cases” groups. For example, 91% of those in the screened group smoked, as compared with only 58% of the other cases group. Also, the cancer found in the screened group was more limited.
The treatment of lung cancer was also different in the two groups. Radical surgery was performed in 37% of men with lung cancer in the screened cases group and in 19% of men with lung cancer in the other cases group. In both groups, 48% of the men were treated with radiotherapy or chemotherapy.
Survival rates were almost twice as good in the screened group as in the other cases group: 19% of men in the screened group and 10% of men in the other cases group were alive 5 years after diagnosis.
Investigators noted that if those in the “others” group who had chest radiography were excluded from the analysis, the difference in survival rates between the two groups would be even greater. They emphasized, however, that there were several factors that were only partly controlled for, and that the results should be interpreted cautiously.
Interpreting the Data
In an accompanying editorial in Chest, Gary Strauss, MD, of the Dana-Farber Cancer Institute at Harvard Medical School, pointed out that the study may be subject to some biases, including that of patient selection. At the same time, he noted that the results of the study cannot be completely explained on the basis of selection bias because the results confirm the major findings of four randomized population trials.
Dr. Strauss added that “these results (also) provide powerful evidence that chest radiography screening does not lead to the overdiagnosis of lung cancer.” He added: “Proper interpretation of cancer early detection trial is exceedingly complex. However, the significant stage distribution, resectability, and long-term survival advantages reported in this new study, which confirm similar findings from randomized population trials, represent solid evidence that chest radiography screening can save lives.”
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