Breast Cancer Survival: Small Occult Metastasis Insignificant
According to a report published by the New England Journal of Medicine yesterday, breast cancer survival rates are not significantly impacted by small occult metastasis. The researchers therefore concluded that further analysis of initially negative sentinel lymph nodes does not add any clinical benefit.
When a patient receives the diagnosis of breast cancer the next step is to undergo further assessment to determine whether or not the cancer cells have spread, or metastasized, to surrounding tissue. Typically, when breast cancer spreads, it spreads first to the closest lymph node, called the sentinel lymph node (SLN) before spreading to other nodes. The question for the researchers was whether or not the initial SLN examination was sufficient enough or if a more aggressive and invasive axillary dissection (removal of between 30-35 nodes in the surrounding tissue) was correlated with a higher breast cancer survival rate.
Researchers at the University of Vermont, as a part of the National Surgical Adjvuant Breast and Bowel Project (NSABP) randomly assigned 5,611 women with breast cancer, but clinically negative axillary nodes, to two different groups. One group underwent SNL biopsies and the other SNL biopsy plus axillary dissection.
The study found that the difference in the 5-year breast cancer survival rate for patients who were found to have metastasis after undergoing biopsies was minimal. The patients in the SNL-only group had a survival rate of 94.6 percent as opposed to the SNL plus axillary dissection group which had a survival rate of 95.8%. The researchers concluded that the 1.2 percent difference was clinically insignificant and therefore routine axillary dissection is unwarranted.
Senior researcher Donald L. Weaver, M.D. concluded in the report, “sentinel-lymph-node biopsy alone has been widely adopted and endorsed as an alternative to axillary dissection, and the overall outcome in this trial shows no significant disadvantage for women who underwent sentinel-lymph-node biopsy alone as compared with women who underwent sentinel-lymph-node biopsy plus axillary dissection. In general, the overall rate of regional or distant recurrence [of cancer] was low.”
Therefore message is that the less invasive SNL biopsy is sufficient to determine treatment course in breast cancer. The more invasive axillary dissection, even if some small cancer cells are found, does not change the overall long term prognosis of the patient.