A woman with HER2-positive, hormone receptor-negative breast cancer (cT3N2M0) achieves pathological complete response (pCR) after neoadjuvant trastuzumab plus pertuzumab-based chemotherapy. Which treatment strategy is supported by the KATHERINE trial data for her adjuvant phase?

• A Continue pertuzumab for 1 year as it demonstrated improved DFS in pCR patients
• B Switch to trastuzumab emtansine (T-DM1) to improve invasive disease-free survival
• C Olaparib should be offered given the high stage at presentation
• D Trastuzumab alone for 1 year is sufficient given pCR ✓

Explanation

The KATHERINE trial enrolled HER2+ patients with residual invasive disease after neoadjuvant therapy and showed T-DM1 was superior to trastuzumab, improving iDFS by approximately 50% relative reduction in recurrence. However, this patient achieved pCR (no residual invasive disease), and the KATHERINE data did not address the pCR subgroup's need for escalation. For pCR patients, current guidelines (ASCO, NCCN) recommend continuing trastuzumab for 1 year total; T-DM1 is reserved for residual disease. Pertuzumab is not approved as monotherapy continuation, and olaparib is indicated only for germline BRCA mutation carriers.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.