Factors associated with surgical management following neoadjuvant therapy in patients with primary HER2-positive breast cancer: results from the NeoALTTO phase III trial

The NeoALTTO trial showed that dual HER2 blockade nearly doubles the rate of pathologic complete response (pCR) in patients with primary HER2-positive breast cancer. However, this did not translate into a higher rate of breast-conserving surgery (BCS). In NeoALTTO, patients with HER2-positive breast cancer were randomly assigned to either trastuzumab, lapatinib or their combination with paclitaxel before surgery with pCR as the primary end point. We investigated the association between the surgery type and clinicopathological factors and response to treatment, adjusting for the treatment arm. Four hundred and twenty-nine patients were subjected to breast surgery. Two hundred and forty-two (56%) and 187 (44%) patients underwent mastectomy and BCS, respectively. In a logistic regression model, negative estrogen receptor (ER), multicentricity and the presence of a palpable mass before surgery were significantly associated with a low chance of BCS. Conversely, patients with small tumors and those eligible for BCS at diagnosis were managed more with BCS, independent of the treatment arm. Radiological response was not associated with the surgical decision. Tumor characteristics before neoadjuvant therapy play a main role in deciding the type of surgery calling for a clear consensus on the role of BCS in patients responding to neoadjuvant therapy.