Physicians have debated since the 1940s whether to seek out these micrometastases and whether to treat them, said Thomas B. Julian, MD, Associate Director of the Breast Care Center at AGH, Associate Director of Medical Affairs for the AGH-based National Surgical Adjuvant Breast and Bowel Project (NSABP). Dr. Julian and Norman Wolmark, MD, Chairman of both the Department of Human Oncology at AGH and the NSABP were principal investigators for the study.
“The difference in five-year survival between women who underwent additional lymph node testing and those that did not is only 1.2 percent,” Dr. Julian said. “What’s more, 80 percent of women with occult metastases or micrometastases are alive and disease-free eight years post-diagnosis. This is good news for women in that it helps us avoid prescribing chemotherapy or other treatments that will offer them limited benefit.”
The study randomly assigned 5,611 breast cancer patients with clinically negative axillary lymph nodes to undergo either a sentinel node biopsy alone, or a sentinel node biopsy plus axillary dissection. Sentinel nodes are normally the first lymph nodes to receive cancer cells from the breast tumor and can be removed with a small surgical procedure. Tissue from patients with negative sentinel lymph nodes was further analyzed for the presence of occult metastases or micrometastases by immunohistochemistry analysis (IHC).
The overall survival rate for patients with metastases was 94.6 percent, compared to 95.8 percent for patients without metastases. Similar differences were found in disease-free survival and distant disease-free survival.
“A larger metastases, of more than two millimeters in diameter, would be cause for more aggressive therapy,” Dr. Julian said. “But these IHC detected occult metastases or micrometastases appear to be no greater a risk than other factors such as the woman’s age or the size of the initial tumor.”
It’s likely that the tiny metastases are effectively treated by the therapy prescribed for the primary tumor, such as chemotherapy, endocrine therapy or radiation, according to the study.
“The key message here for women is that they do not need to worry about tiny hidden metastases once they have undergone a sentinel lymph node biopsy that is negative for cancer,” Dr. Julian said.
Other investigators in the trial were Donald L. Weaver, MD; Takamura Ashikaga, PhD; David N. Krag, MD; Joan M. Skelly, MS, and Seth P. Harlow, MD, of the University of Vermont College of Medicine and Vermont Cancer Center; Stewart J. Anderson, PhD, of the NSABP Biostatistical Center and the University of Pittsburgh Graduate School of Public Health, and Eleftherios P. Mamounas, MD, of the NSABP and Aultman Cancer Center, Canton, Ohio.