Findings revealed that at a midpoint follow-up of 6.3 years, 435 women had died and 376 experienced recurrence of their cancer. Based on IHC staining, five-year overall survival rates of those whose samples tested positive for node involvement were 95.1 percent, compared to 95.7 percent for those whose SLN biopsies tested negative. Corresponding five-year rates of disease-free survival were 90.4 percent and 92.2 percent, respectively.

Giuliano said the research, when adopted clinically, can save patients several hundred dollars or more in unnecessary tests. Women with microscopic metastases in their SLNs can also be spared from certain more aggressive treatments that were thought to increase their survival rates.

Dr. Lora Weiselberg, chief of breast cancer service at the Monter Cancer Center of North Shore-LIJ Health System in Lake Success, N.Y., said many physicians have questioned the significance of the SLN biopsies evaluated in the study. ???In certain cases . . . we would want to do them anyway, but otherwise I think this is very strong evidence. I think more and more pathology laboratories are going to go in that direction (of fewer tests) because adding another costly test, if it's not going to help the patient, is unnecessary,??? she said.