Implications of a positive sentinel lymph node on treatment strategies

Dr Eline Naert, a medical oncologist at Ghent University Hospital interviews Prof Philip Poortmans from the Iridium Netwerk and University of Antwerp who was invited to share the perspective of the radiation oncologist on a hot topic in the field of breast cancer, namely the implications of a positive sentinel lymph node on treatment strategies.

There is no optimal technique for marking a sentinel lymph node. The choice of technique depends on the experience and proficiency of a specific team rather than a universally agreed-upon method.

The utilization of radioactive iodine emerges as superior due to its ease of use and efficacy. It can be readily removed post-treatment. While in the Netherlands there is extensive expertise with this technique, it is unfortunately not reimbursed in Belgium. A primary objective for the future is establishing consensus on the terminology employed. Discussions regarding axillary marking vary, with terms like TAD or MARI used, contingent upon the technique. Despite these differences, the fundamental concept of marking remains consistent, regardless of the technique employed.

When determining the indication for marking, both the technique and timing assume critical roles. In the context of primary systemic therapy, timely marker placement is crucial since some markers, such as metal clips or magnetic seeds, can persist in patients for months. While these markers may interfere with magnetic imaging techniques of iodine, they have no impact on CT and MRI imaging.

A key takeaway from this discussion is the importance of understanding and correctly applying the chosen technique. In the clinical realm, the decision to proceed with adjuvant therapy is guided by the outcomes of lymph node dissection. Experts emphasize the significance of minimizing the number of dissected lymph nodes to preserve shoulder function and reduce the risk of lymphedema.

In the case of post-primary systemic adjuvant treatment, reimbursement is contingent on harvesting a minimum of 4 lymph nodes, a practice met with criticism. Given that the sentinel node differs from the targeted axillary dissected marked node, the dissection of 2 lymph nodes should suffice. Even if this approach results in some false negative outcomes, radiation therapy can effectively eliminate residual tumour cells left in the node. This is particularly relevant for patients who transition from clinical node positivity to node negativity.

When tumour cells are identified in the removed lymph nodes following primary systemic treatment, the conventional approach is lymph node dissection, although this standard is currently under scrutiny. In such cases, radiation therapy can eradicate a substantial number of tumour cells. Accurate imaging is pivotal; reliable negative results indicate that routine elective radiation therapy can achieve curative outcomes in the majority of cases.

In instances where invasive disease is detected in the lymph node section, there is reduced hesitance in performing dissection. However, it is crucial to recognize that axillary surgery is not curative but holds predictive and prognostic value.

Current research endeavours explore the possibility of safely omitting sentinel lymph node biopsy from treatment protocols. Certain subgroups of patients, determined by patient-related factors such as age, general condition, tumour-related T-stage and treatment plan, could benefit from this approach. Ongoing research, particularly from leading experts in the Netherlands, is expected to provide valuable insights, potentially allowing for the omission of sentinel lymph node biopsy in specific patient populations.

References:

Dubsky P. – A surgeon’s perspective. ESMO2023

de Azambuja E. – A medical oncologist’s perspective. ESMO2023

Poortmans P. – A radiation oncologist’s perspective. ESMO2023