The clinical case for TAD: management of the axilla post-NAC

Abigail Caudle, MD, pioneer of the TAD technique, recently took the virtual stage at the annual congress of the French Society of Oncological Surgery (also known as the SFCO).

In the session watched by over 700 physicians, she explained how embracing TAD has vastly improved the accuracy of her team during axillary surgery, with the Magseed®marker playing a crucial role as the “definitive axillary node marker”.

The evolution of axilla assessment

Thanks to the effectiveness of neoadjuvant chemotherapy (NAC), up to 70% of node positive patients can convert to node negative after treatment. But the crucial question is: how can we prove with accuracy that this has happened?

In her talk, Dr Caudle explained that previously there were two techniques most common to assess the axilla.

  • Sentinel lymph node dissection (SLND) – which carries a false negative rate of roughly 13%.
  • Axillary lymph node dissection (ALND) – which involves removing several nodes and can present serious risks.

After an ALND procedure, on average 7 in 10 patients can experience difficulties with morbidity, including general pain, limited range of motion – or in the worst cases, lymphedema.

Marking the path to success

This is where marking techniques came in, said Dr Caudle. Her team analysed a sub-set of patients in the Z1071 trial (Boughey et al, 2015), where a clip had been placed in the positive lymph node at the time of biopsy, with both removed after chemotherapy.

When the clipped node was retrieved, the false negative rate of the SLNB was reduced to 6.8% – a significant discovery.

“If the biopsied lymph node is a reliable predictor of the other lymph nodes… is it possible to localize and selectively excise that node?”Abigail Caudle, MD MD Anderson

In their first attempt Dr Caudle’s team analysed 191 patient cases, where the nodes displaying metastases were clipped for removal later on. At this first attempt, the team managed to reduce their false negative rate to 4.2%.

However, in roughly a quarter of cases, the clipped node is not the sentinel node. With that in mind, Dr Caudle and her team decided to take her trial a step further and analyse both the clipped node and the sentinel nodes, the latter identified using a dual tracer mapping agent.

They conducted a separate SLND on a sample of 118 patients, with 74 patients having a node with metastases clipped alongside a SLND. Within this group, it was found that pairing the two reduced the false negative rate once again to a remarkable 1.4%. A new, game-changing procedure – targeted axillary dissection (TAD) – had been established.

Spreading the word

Similar studies to Dr Caudle’s are now regularly taking place around the world. In a survey conducted by her team, 82% of members of the American Society of Breast Surgeons now believe marking biopsied nodes before removing them is “critical”.

But 73% are still using wires, with 13% using radioactive seeds. It’s been proven that wire localization can be inaccurate and outdated, while access to radioactive seeds remains a considerable issue.

“We really wanted to explore the possibility of localizations with non-radioactive sources. This is where magnetic seeds came into the picture”Abigail Caudle, MD MD Anderson

The final step: a tiny seed

Dr Caudle and her colleagues soon discovered the Magseed® marker and began initially trialling it for tumour localization. Their initial study involved 10 surgeons and 17 radiologists and found Magseed easy to accurately place and just as easy and accurate to remove breast the breast lesions. They had found the solution they were looking for.

In a subsequent trial using Magseed for TAD, Magseed® markers were placed accurately in the clipped nodes for 50 patients, with all seeds retrieved successfully, taking just over six minutes on average. In all cases, the seeds stayed within the nodes for retrieval, a frequent concern when using wires particularly. What’s more, 86% of surgeons rated the process as “easy” upon first use, with only 4% initially rating it as “difficult”, before later confirming it to be much simpler.

Since then, Dr Caudle has become an advocate and long-term user of the Magseed® marker. She is currently in the recruiting phase for her latest trial, Magseed Enabled Long-Term Localization of Axillary Nodes (MAGELLAN). The MAGELLAN trial aims to place the Magseed® in the node at the time of biopsy, saving patients an additional procedure.

"We no longer use radioactive seeds at MD Anderson"Abigail Caudle, MD MD Anderson

In conclusion, Dr Caudle stated that magnetic seeds are the future for this revolutionary technique, eliminating the risk and burden of radioactivity solutions, and that she believes there is potential for magnetic seeds as the “definitive axillary node marker”.