Doctors have come up with a screening test that can detect lung cancer early, but a new study from the Journal of the American Medical Association concludes that the screening may actually be harmful, provoking unnecessary surgery, reported The New York Times.
Last fall, The New England Journal of Medicine published the study concluding that spiral CT screening would help cure most forms of lung cancer by enabling physicians to detect it early and offer treatment before it grows. But the conflicting JAMA study reported that spiral CT screening may incite needless surgery that could potentially cause death. Some people would receive treatment that they don’t require and could only cause damage. Five percent die within a month after having lung surgery.
These two studies showed conflicting reports because one focused on increased survival, while the other focused on mortality. “Finding cancer early saves lives only if two conditions are met: the cancers detected are the ones that kill people; and early treatment prevents these deaths,” reported the Times.
The CT screening could detect some lung cancers that wouldn’t cause symptoms or death, resulting in overdiagnosis. Not all cancers are progressive. Research in screening has demonstrated that cancer encompasses a broad spectrum of disorders: some cancers rapidly progress to death, some do so more slowly, and some don’t progress at all (or may even regress), said the Times.
The New England Journal study reported screening about 31,000 people with spiral CTs and finding 484 with lung cancer. These patients had a 10-year survival rate of 80 percent — compared with 10 percent for current lung cancer patients in the United States. The JAMA study reported screening about 3,200 people and finding 144 with lung cancer. (The detection rate was higher because this study had older patients and longer follow-up.) Of 3,200 people, 38 died from lung cancer — the same mortality rate expected for people of similar age and smoking history in the absence of screening.
In short, The New England Journal reported increased survival; JAMA reported no difference in mortality, according to the Times. Overdiagnosis inflated both the survival statistic (number alive at a specified time) and the number of diagnoses. For the mortality statistic, overdiagnosis has no effect on the number of deaths or the number studied. For example, if we told all the people in the country that they had lung cancer today: lung cancer mortality would be unchanged, but lung cancer survival would skyrocket. To avoid repeating these mistakes, The Times reported that we should not screen for lung cancer unless the trials demonstrate a reduction in mortality.