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Patients with lymph node-positive breast cancer may still avoid extensive axillary surgery if they have clear nodes after systemic therapy, data from a prospective registry showed.

Patients with clear nodes after systemic therapy had an axillary recurrence rate (aRR) of 2.9% with radiation therapy (RT) alone as compared with 3.5% among patients with residual tumor in nodes and treated with surgery and RT. After a median follow-up of 44 months, invasive disease-free survival (iDFS) was 89% in the RT-only group and 82% among patients treated with surgery and RT. Overall survival (OS) was 95% and 90% in the two patient groups.

Using sentinel lymph node biopsy and marking axillary nodes with radioactive iodine (MARI) seeds showed the feasibility of omitting axillary dissection in selected patients with lymph node-positive breast cancer, reported Annemiek Van Hemert, MD, of the Netherlands Cancer Institute in Amsterdam, at the European Breast Cancer Conference in Milan.

"If we are able to predict the response based on the removal of only one lymph node, it means we can safely avoid extensive removal of the lymph nodes if no living tumor cells are left," Van Hemert said in a statement. "This will avoid serious complications, such as painful swelling in the arm, known as lymphedema."

"Although clinicians use a number of staging techniques to predict the response, until now robust data on cancer outcomes have been lacking, especially in patients whose cancer has spread to more than three lymph nodes," she added.

The results with the MARI technique showed that Van Hemert and colleagues accomplished the goal of applying effective therapy to breast cancer while limiting harm to patients, said Fiorita Poulakaki, MD, PhD, of Athens Medical Centre Hospital in Greece.

"The results from this study suggest a way to help us avoid side effects that affect the quality of life and can sometimes cause considerable long-term distress to patients," said Poulakaki, who was not involved in the study. "Every day we cure patients, making sure they live long lives, but at the same time, we should care also about survivorship issues. We look forward to further results from this trial."

Axillary lymph node staging techniques, such as MARI and targeted axillary dissection, after primary systemic therapy have low false-negative rates, which has stimulated interest in tailored axillary treatment, including omission of axillary lymph node dissection, Van Hemert and colleagues noted in their introduction. However, robust data on oncologic outcomes after tailored axillary treatment are lacking, particularly for patients with extensive nodal disease.

Investigators conducted a prospective registry study from 2014 to 2021 to evaluate the use of the MARI technique in patients with newly diagnosed early breast cancer and more than three suspicious lymph nodes. Nodal stage was assessed by PET-CT prior to systemic therapy. After completion of systemic therapy, the MARI node was excised and evaluated for response. Patients who achieved a pathologic complete response (pCR) received only axillary radiation, whereas patients with residual tumor in the MARI node underwent axillary node dissection, followed by RT.

The primary endpoint was aRR and secondary endpoints included iDFS and OS. Data analysis included 218 patients whose disease was distributed among the following subtypes: 39% hormone receptor (HR)+/HER2-, 19% HR+/HER2+, 17% HR-/HER2+, and 25% triple negative. PET/CT identified extra-axillary lymph nodes in 39% of the patients.

Primary systemic therapy achieved pCR in 47% of patients (103 of 218) who were treated with RT alone. The remaining 53% (115 of 218) of patients had residual disease in the MARI node and had surgery and RT.

The overall study population had an aRR of 3.2%, iDFS of 85%, and OS of 93%. The trial met the primary endpoint, showing no significant difference in aRR between patients who received only RT and those treated with surgery and RT. Analyses of iDFS and OS produced overlapping confidence intervals for the two treatment strategies.

"We hope that other clinicians will think of implementing this de-escalation strategy so that more patients with breast cancer will benefit from what we have shown," said Van Hemert. "Surgical removal of axillary nodes can be safely omitted in about 80% of patients treated with primary systemic therapy."

Investigators intend to continue collecting outcomes data for the patients over a longer follow-up period. Van Hemert said another trial of de-escalation has already begun, investigating the safety of omitting RT in selected patients with tumors smaller than 2 cm, no evidence of nodal involvement, and a pCR after systemic therapy.

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