Breast Cancer Experts Debate the Value of Axillary Imaging
Evolution of axillary clinical management over a decade has led to controversy
Should every woman with newly diagnosed breast cancer get axillary imaging? That was the question debated by two foremost experts in the field during RSNA 2020.
“Axillary nodal management has undergone quite a historical evolution. That is important context for understanding where this controversy comes from in the role of imaging for breast cancer patients,” said Victoria Mango, MD, associate radiologist and co-director, Breast Imaging Education and Training at Memorial Sloan Kettering Cancer Center.
Dr. Mango explained that conventional treatment of a breast cancer patient used to include an axillary lymph node dissection.
“But more recent data shows that it was safe to do a sentinel lymph node procedure instead,” she said. “In this procedure, the first few lymph nodes draining the area are checked with surgical excision, and if negative, no further surgery is needed. If positive, a patient would go on to an axillary lymph node dissection.”
This approach has evolved over the last decade, Dr. Mango said. Currently, if the sentinel lymph node is positive, the patient may or may not go on to an axillary lymph node dissection.
“It’s really these changes to the clinical and surgical approach to axillary management that leads to this controversy,” Dr. Mango said. “When is it appropriate to do preoperative axillary imaging evaluation?”
Impact of ACOSOG Trials
Regarding preoperative axillary imaging and early-stage cancers, Dr. Mango focused on the American College of Surgeons Oncology Group (ACOSOG) Z0011 trial first published in 2010 and 2011. Numerous updates have followed.
The study evaluated survival and locoregional recurrence in patients with T1 or T2 disease and no palpable nodes with one or two positive sentinel nodes who were randomized to undergo axillary lymph node dissection after sentinel lymph node biopsy, compared to sentinel lymph node biopsy alone.
“The study concluded that despite the potential for residual axillary disease after sentinel lymph node biopsy, sentinel lymph node biopsy without axillary lymph node dissection offers excellent regional control with equivalent survival,” Dr. Mango said.
“What Z0011 means for radiologists is that preoperative axillary imaging is really only going to be helpful if we can help tell the surgeon which patients can go right to axillary lymph node dissection,” Dr. Mango said. “Can I tell with imaging if they have one or two positive nodes versus three or more nodes, which is going to be that cut-off for whether or not they are going to meet that Z0011 criteria?”
Essentially, it means less is more, she continued. “But the logical question is can I preoperatively accurately identify those women who need an axillary lymph node dissection and prevent them from going through a sentinel lymph node biopsy if ultimately we can tell they need more?”
Dr. Mango argued that for clinically T1- and T2-node negative patients, preoperative axillary imaging is only beneficial if it demonstrates which patients require axillary lymph node biopsy and that the axilla should be managed by the sentinel lymph node biopsy results, and not by ultrasound (US) findings or US biopsy results.
Several studies have demonstrated that routine axillary US in that setting can only make this prediction in 30% of patients but may expose the other women to unnecessary axillary node biopsies.
“Surgical management of the axilla in breast cancer patients is extremely controversial and continues to evolve, with multiple clinical trials ongoing.”
Gaiane Maia Rauch, MD, PhD
Radiologists, Surgeons Must Communicate
On the other hand, Gaiane Maia Rauch, MD, PhD, professor of radiology, co-lead of the Breast Cancer Moonshot Flagship Project, Division of Diagnostic Imaging, University of Texas MD Anderson Center, Houston, argued that there is a place for axillary US, even in light of the findings of the Z0011 trial.
Regional nodal US frequently changes the initial clinical stage and plays a valuable role in treatment planning. It is important in determining the extent of nodal burden and particularly in evaluating clinically occult N2 and N3 disease, Dr. Rauch said. Axillary US helps triage patients who require axillary lymph node dissection and therefore can avoid sentinel lymph node biopsy. Dr. Rauch added that sentinel node biopsy itself may represent surgical over-treatment in patients with early breast cancer and negative axillary US.
“It helps in treatment, may change the extent of the radiation field, may divert patients to neoadjuvant systemic therapy, and might guide the need and correct extent of axillary surgery,” she said.
Drs. Mango and Rauch also examined the controversy in the neoadjuvant setting. Dr. Mango maintained that axillary imaging before or after neoadjuvant chemotherapy does not reliably indicate which patients will need axillary lymph node dissection after chemotherapy.
“The axilla really does need to be managed based on the sentinel lymph node results, not by ultrasound findings or ultrasound biopsy results,” Dr. Mango said. “Ultimately it’s a team approach.”
Radiologists need to have dialogues with the surgeons and oncologists at their institutions to get an understanding of the surgeon’s approach to sentinel lymph node biopsy, she added.
“Do they use the dual tracer? Do they look for three or more sentinel lymph nodes? Because when you read the literature you have to have this context in order to apply it appropriately to your own practice,” Dr. Mango said.
Axillary US also helps abnormal node identification, biopsy clip placement and localization, Dr. Rauch said. She pointed out that axillary US has helped achieve a false negative rate of less than 10% in patients with node-positive breast cancer after neoadjuvant systemic therapy and who have limited axillary surgery such as targeted axillary dissection, or the radioactive iodine seed localization in the axilla with the sentinel node procedure.
“It helps avoid overtreatment with axillary lymph node dissection of this patient population,” Dr. Rauch said. “And it helps avoid axillary surgery in triple negative breast cancer and HER2+ breast cancer patients who have breast pCR [pathological complete response] after neoadjuvant systemic therapy and negative axillary US at staging.
“Surgical management of the axilla in breast cancer patients is extremely controversial and continues to evolve, with multiple clinical trials ongoing,” she said. “Radiologists must communicate with their referring surgeons to determine the best management plans for their patients.”
The debate was moderated by Maxine Jochelson, MD, director of radiology at the Evelyn Lauder Breast and Imaging Center and attending radiologist at Memorial Sloan Kettering Cancer Center.
The outcome of the Z0011 trial proves that after sentinel node surgery, there could be small amounts of disease remaining in the axilla in women receiving radiation and/or systemic therapy without decreasing disease-free or overall survival. This suggests that the contributions of imaging are only part of the equation. Dr. Jochelson noted that while the two presenters drew exact opposite conclusions, patients at both institutions do well.
“Although we disagree in many ways, we also agree on many things,” Dr. Jochelson said. “At the end of the day, we are looking for outcomes.” She concluded with a reminder that those outcomes indicate we all take great care of our patients.
“That’s the main goal,” Dr. Rauch agreed.
For More Information
Watch the RSNA 2020 Controversy Session, “To Look or Not to Look—Does Every Woman with Newly Diagnosed Breast Cancer Need Axillary Imaging?” at RSNA2020.RSNA.org.
Read previous RSNA News stories on breast cancer imaging:
- Digital Breast Tomosynthesis Improves Invasive Cancer Detection
- AI Tool Improves Breast Cancer Detection on Mammography
- Tomosynthesis with Synthetic Mammography Improves Breast Cancer Detection