In the study, a team led by Dr. Hiram S. Cody III, a professor of clinical surgery at Memorial Sloan-Kettering Cancer Center in New York City, analyzed a population of 368 patients who were originally diagnosed with breast cancer in the 1970s.
At the time, these patients were judged to be free of cancerous cells on the basis of a single tissue slice (standard procedure at that time).
As a result of that diagnosis, these patients received no follow-up treatment for their disease.
Each of these patients was then monitored over the following 20 years or so.
team retrospectively reanalyzed the decades-old tissue samples using modern techniques.
They then assessed how many of the slices did, in fact, contain cancerous cells, and whether those stray cancerous cells had affected the women's survival.
"What we found was that among these patients, 23 percent were converted to node-positive [cancer status], and among those who were converted, their survival was worse than among patients who remained node-negative," said Cody
"The 23 percent number is very significant, because it argues that if pathologists just do one section, you may want to ask them to do more," he
"We think the information you get by doing more is significant."
According to Cody
, 30 years ago the standard of care for breast cancer patients was complete dissection of the axillary lymph nodes (those found under the armpit) followed by cell-shape analysis using a single tissue slice from each node.
That reduction in work per node has a real payoff, because pathologists can delve much deeper into each sample, Cody
"Because you remove fewer nodes, you can study them more carefully, and we argue that the information you get by doing that is prognostically significant," he
Current guidelines from the College of American Pathologists recommend analyzing one tissue slice per biopsied lymph node, Cody
Yet for years, he
said, physicians have known that the more carefully one looks, the more cancerous cells one can find.
noted one "significant caveat" to this study: Because breast cancer survival and treatment regimens have changed so dramatically over the past 30 years, this study says nothing about the prognostic implication of micrometastases discovered today.
That will require prospective studies, several of which are ongoing.
said, "because we don't know the results of those studies yet, studies like our own may be the best available evidence at present, and our study suggests these micrometastases are prognostically significant."
SOURCES: Hiram S. Cody III, M.D., attending surgeon, professor, clinical surgery, Breast Service, department of surgery, Memorial Sloan-Kettering Cancer Center, New York City; Stephen F. Sener, M.D., professor, surgery, Northwestern University Feinberg School of Medicine, Chicago; April 10, 2008, Journal of Clinical Oncology