When does a difference make a difference? That's a question that Samuel Finlayson, M.D., and Ian Paquette, M.D., have been pondering, in the context of a recent finding that urban patients tend to be diagnosed with cancer later in the disease's progression than do patients who live in rural areas.

Age: "The difference between the two populations was statistically significant, but the absolute difference was not that great," says Finlayson, an associate professor of surgery. He and Paquette, a resident in general surgery, published their finding in the Journal of the American College of Surgeons. They based their study on data collected by the National Cancer Institute about cancers of the colon and lung and controlled for factors such as age, race, gender, marital status, income level, and level of education. Though the difference between urban and rural patients wasn't great, the researchers were interested in the the direction of the difference, for the previous assumption had been that rural patients were diagnosed later.

"What's more notable," Finlayson adds, "is the very high proportion of people presenting with late stages [in] both populations.

The difference was
statistically significant,
but "not that great."

That's probably the more striking finding—evenmore striking than the small differences that we saw between the urban and the rural populations." Colon and lung cancers are "both very common cancers and major health problems in the U.S.," points out Paquette. The two cancers, says Finlayson, "can both present at a very wide range of stages, with very different prognoses."

Colon cancer, when identified early, can be surgically removed; such patients have an average five-year survival rate of greater than 90%. But when it's found at a more advanced stage, colon cancer is virtually incurable. That's why regular screening for colon cancer is highly recommended, especially since the disease's risk factors are not very well understood.

For lung cancer, on the other hand, there is no nationally recognized screening recommendation, though an effort to identify one is currently under investigation in a major multicenter trial (DHMC is one of the participants in this trial).Also, there is a clear and undisputed risk factor for lung cancer—smoking—unlike colon cancer, where most cases are sporadic.

"There is certainly a need for a cost-effective way of screening for lung cancer," says Paquette. But, adds Finlayson, "if we were to allocate resources to screen for lung cancer or to prevent smoking, it would probably bemore cost-effective to prevent the disease in the first place than to try and find [tumors] after they have evolved."

Inquiring: So a study that was designed to assess whether there's an urban-rural diagnosis differential led to ruminations on the effectiveness, and cost-effectiveness, of screening methodologies.Maybe that's a mark of truly inquiring minds.