A provocative though small study suggests that the very act of quitting smoking may be a symptom of not-yet-diagnosed lung cancer.

That’s the curious conclusion that researchers at Thomas Jefferson University in Philadelphia reached after they surveyed 115 lung cancer patients, all of them current or former smokers, at the Philadelphia Veterans Affairs Medical Center. The team, led by Barbara Campling, asked when the patients had stopped smoking relative to their diagnosis and onset of symptoms and how difficult or easy it had been to quit. The researchers also used a standard tool called the Fagerstrom Test for Nicotine Dependence to calculate how deeply addicted the smokers had been to nicotine at the peak of their habit.

The researchers, whose work appears in the March issue of the Journal of Thoracic Oncology, undertook the study on a hunch: They had observed that many of their lung-cancer patients had quit smoking before they were diagnosed, often without consciously deciding to do so. The scientists were aware of the common belief that people typically quit smoking in response to the appearance of symptoms suggestive of lung cancer. But they weren’t convinced that was really how things work.

Their study appears to bear out their hunch. They learned that 55 of the 115 patients had quit smoking before being diagnosed, all but six of them before any cancer symptoms appeared. Of those who quit, 31 percent reported they’d done so with ease – but not because they had never been addicted: Their levels of addiction when they were smoking the most had been the same as the levels of those who hadn’t quit.

The authors suggest that the presence of a lung-cancer tumor may somehow block the body’s uptake of, or desire for, nicotine; perhaps, they surmise, such tumors may secrete a chemical that makes that happen.

They acknowledge that their work has limitations, among them the small sample size and the fact that the data were self-reported and after the fact. Still, they believe they’re on to something that should be investigated further.

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