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Patients with early lymph node-positive breast cancer and pathologic complete response (pCR) after neoadjuvant therapy had similar long-term recurrence rates and survival regardless of the type of adjuvant therapy they received, a Dutch registry study showed.

After a median follow-up of 6 years, regional recurrence rates ranged from 3.0-4.1% whether they had conservative axillary surgery with or without axillary radiation therapy (RT) or complete lymph node dissection (ALND) with or without RT. The 5-year disease-free survival (DFS) was 84.7% (range 81.7% to 89.6%) and overall survival (OS) 90.1% (range 88.4% to 95.0%).

"Omitting ALND and RT in patients with ypN0 resulted in excellent 5-year disease-free and overall survival," said Sabine R. de Wild, MD, of Maastricht University in The Netherlands, during the in Milan. "Of course, there is heterogeneity that we need to address, so additional analyses will be performed. We are also very interested in patients with ypN-plus, or residual disease, after systemic therapy and we will also look further into breast cancer molecular subtype."

Decisions about adjuvant therapy require consideration of multiple factors, beginning with tumor subtype, said Nancy Chan, MD, of NYU Langone Health's Perlmutter Cancer Center in New York City.

"While it is true some patients who achieve pCR can safely omit ALND and RT, it is really important to incorporate the tumor subtype," Chan, who was not involved in the study, told MedPage Today via email. "The adjuvant therapy options are very different across molecular subtypes. For example, in hormone receptor-positive[HR+]/HER2-negative patients, adjuvant endocrine therapy significantly lowers risk of recurrence. Some patients are also candidates for adjuvant CDK4/6 inhibitors. In HER2-positive breast cancer, HER2 targeted therapies similarly lowers risk of recurrence."

"In some higher clinical risk molecular subtypes, such as triple-negative breast cancer (TNBC, Basaloid tumors), it may not be appropriate to omit ALND and RT," she added. "In practice, within our multidisciplinary group, we review each patient's clinicopathologic stage, additional features of tumors (is there lymphovascular invasion, extranodal extension, etc.) and make a personalized treatment plan."

Clinically node-positive (cN+) breast cancer often is treated with neoadjuvant systemic therapy. Following surgery, a variety of axillary staging and treatment strategies are available for patients with cN+ breast cancer, said de Wild. Treatment strategies include less invasive axillary staging, and ALND may be omitted or replaced by RT in some instances.

To examine 5-year outcomes with different adjuvant strategies, investigators analyzed data from the registry, a retrospective registry with data for about 4,000 patients with early breast cancer and one to three (cN1-3) involved lymph nodes. The principal outcomes of interest related to oncologic safety, including regional recurrence and 5-year DFS and OS.

The analysis included 3,550 patients with breast cancer diagnoses during 2014-2017 and one to three biopsy-proven axilla metastases. All patients received neoadjuvant systemic therapy (with or without targeted therapy), followed by breast-conserving surgery and axillary surgery. Patients were categorized according to the type of adjuvant therapy: 325 patients had neither ALND nor RT, 1,160 had RT without ALND, 597 had ALND without RT, and 1,468 had both ALND and RT.

A majority (54.3%) of patients had HR+/HER2- breast cancer, followed by HR+/HER2+ (15.1%), HR-/HER2+ (12.7%), and TNBC (17.9%). A third of patients with HR+/HER2- disease did not have ALND or RT, as compared with 19-26% of the other subtypes. Overall, 80.9% of patients had one positive lymph node, 3.4% had two positive nodes, and 15.3% had three involved nodes. ALND and RT were omitted for 92.9% of patients with cN1 status, 1.5% of patients with cN2 disease, and 5.5% of cN3 disease.

Surgery distribution was mastectomy in 53.3% of all patients and lumpectomy in 46.7%. Lumpectomy was the predominant form of surgery for patients who did not have ALND or RT (60%) and those who had RT without ALND (59%), whereas mastectomy was more common for who had ALND without RT (54.0%), and both ALND and RT (65.7%).

Overall, 36.8% of patients had ypN0 status after neoadjuvant therapy, including 81.2% of patients who skipped ALND and RT versus 24.0% of patients who had ALND and RT, to 44.1% of patients who had ALND alone, and 36.8% of those who had axillary RT but not ALND.

For the entire cohort, the regional recurrence rate was 6.3% (range 4.1-8.0% according to adjuvant treatment). DFS was 77.7%, including 86.9% for patients who skipped ALND and RT (vs 71.1% among patients who had both). The 5-year OS was 85.0%, highest for patients who skipped ALND and RT (92.6%) and lowest for patients who had both (79.8%).

Among 1,306 patients with ypN0 status after neoadjuvant therapy, regional recurrence rates were 3.6% overall, 3.0% in patients who had neither ALND nor RT, 3.5% with RT alone, 4.1% with ALND alone, and 3.7% with both. OS was 90.1% overall, 95.0% without ALND or RT, 89.0% with RT alone, 89.3% with ALND alone, and 88.4% with ALND and RT.

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