Both Australian and New Zealand breast cancer guidelines recommend that if sentinel node biopsy (removal and testing of the first lymph node or nodes to which cancer cells are likely to spread, called sentinel lymph nodes) results indicate that sentinel lymph nodes contain cancer cells (positive), a completion axillary lymph node dissection (surgery to remove more nodes in the armpit) should be performed. If the sentinel nodes do not contain cancer cells (negative), the axillary lymph nodes (nodes in the armpit) should be observed only.
Patients whose treatment followed recommendations
This study showed that best practice recommendations were adhered to in the majority of cases (80% of those with positive sentinel nodes and 90% of those with negative sentinel nodes).
Patients with positive sentinel nodes but no further surgery
The study found that 20% of patients with positive sentinel lymph nodes did not go on to have a completion axillary lymph node dissection, despite treatment recommendations.
Patients were less likely to undergo this further procedure if they were over 70 years of age. Elderly patients are commonly managed differently as treatment will have less impact on long-term survival and more impact on general health compared with younger patients.
Patients were also less likely to undergo further axillary surgery if they had fewer positive sentinel nodes compared with negative sentinel nodes. This is consistent with data from other studies showing reduced likelihood of additional positive nodes on axillary dissection for patients with increasing numbers of negative sentinel nodes.
Patients with negative sentinel nodes who had further surgery
In cases where no cancer cells were found in the sentinel lymph nodes, 10% of patients went on to have completion axillary lymph node dissection, despite treatment recommendations.
Patients were more likely to have this further procedure if they were under 40 years of age, had a tumour over 3 cm, had a more aggressive (higher grade) tumour, or the cancer had spread to the blood vessels or lymphatic channels. All of these are commonly recognised predictors of poor outcomes and would be known by the surgeon within a short time of the sentinel node biopsy. It is also possible that some of these patients had isolated tumour cells (less than 2 mm area of tumour cells), which are not recorded in the audit.
For patients who did go on to have a completion axillary dissection despite a negative sentinel node biopsy, 20% were found to have cancer cells in the axillary lymph nodes. The cancer was more likely to have also spread to the blood vessels or lymphatic channels in these 20%, compared with patients where the completion axillary dissection was also negative.