Is Underarm Surgery Necessary After Breast Cancer Treatment?

🔍 What Is the MARI Protocol?

• MARI is an abbreviation for "Marking the Axillary lymph node with Radioactive Iodine seed". In other words: "Marking the axillary lymph node with a radioactive iodine seed".
• A clinically positive axillary lymph node is marked just before neoadjuvant treatment begins with a small metallic seed containing radioactive iodine-125. This seed is not therapeuticand is used only for localization.
• The iodine seed emits a very low dose of radiation, stays in place, and does not spread through the body. It allows the surgeon to locate the same node easily after treatment.
• Neoadjuvant (preoperative) systemic treatment (chemotherapy or targeted therapy) is completed, after which the marked lymph node is removed.
• Pathological examination of the removed node shows the treatment response, and the surgical plan is based on this result.

📊 Striking Study Numbers

• Number of Patients: 350 breast cancer patients with clinically positive axillary nodes.
• Pathological Complete Response (pCR) Rate: Among the patients, 39%(n=135) had a complete pathological response (pCR) in the marked lymph node.
• Recurrence in Groups Without ALND: Only 0.7% axillary recurrence.
• 5-Year Overall Survival: 98%.
• Patients With Residual Disease in the Lymph Node: After radiotherapy, the axillary recurrence rate was 2.3%; all of these patients also had concurrent distant metastases.

🗣️ Commentary

This study strongly indicates that axillary dissection may be unnecessary for many patients.

In patients with a limited axillary tumor burden on pretreatment assessment, the oncological benefit of ALND was clearly shown not to outweigh its surgical morbidity and complication risks.

Clinical Implications

• The MARI protocolindividualizes axillary surgery, significantly reducing unnecessary ALND.
• Definite Indications for ALND: A clinically high axillary tumor burden, multiple (>3) macrometastases, matted axillary nodes, persistent nodal masses despite treatment, or prominent nodal disease on PET-CT.
• Groups Requiring Caution: Aggressive tumors with triple-negative or HER2-positive biology.
• Radiation Safety: Although the iodine seed has low radioactivity, safety precautions must be taken when implementing the protocol.
• Impact on Guidelines: This approach has been included in national guidelines in the Netherlands since 2022 and has fundamentally changed clinical practice.