Why is Sentinel node biopsy essential for the treatment of early breast cancer ?

When breast cancer is suspected to have spread to the lymph glands in the axilla(armpit),the standard procedure is to do an axillary dissection (removing all axillary lymph nodes). However, in early breast cancer, when the nodes appear clinically normal, there is a dilemma whether to do a complete axillary dissection or not because only around 30% of these nodes actually turn out to be involved by cancer on pathology. Complete axillary dissection has side effects like lymphedema (swelling) of the arm, loss of sensation or developing abnormal sensation over upper arm, fluid collections in the axilla,etc. Presently, the best way to assess (stage) the axillary lymph nodal involvement is the sentinel lymph node biopsy (SLNB) technique.

A sentinel lymph node is defined as the first lymph node to which cancer cells are most likely to spread from a primary tumor. Sometimes, there can be more than one sentinel lymph node.

To locate a sentinel node, the surgeon injects a tracer dye near the tumor. The surgeon then uses a device to detect lymph nodes in the axilla that take up the dye. Once the sentinel lymph node is located, the surgeon makes a small incision on the overlying skin and removes the node and sends for a frozen section biopsy which is reported by the pathologist immediately in a few minutes. If the sentinel node shows tumor cells on microscopic examination ,then it is called as a positive SLNB. If not, it is called as a negative SLNB.

A negative SLNB result suggests that cancer has not yet spread to regional nodes and no further axillary dissection is required. In these patients, the complications of a complete axillary dissection maybe avoided.  A positive SLNB result indicates that cancer has spread to the regional lymph nodes. In these situations, it is mandatory to perform a complete axillary dissection.  

If the SLNB facility is not available at a treatment center, the standard practice would be to perform a complete axillary dissection which is over treatment in about 70% of the patients.

“Sentinel lymph node biopsy technique has become the standard of care procedure worldwide for all early stage  breast cancer patients who do not have palpable axillary lymph nodes”