Pertuzumab (P) + trastuzumab (T) with or without chemotherapy both followed by T-DM1 in case of progression in patients with HER2-positive metastatic breast cancer (MBC) - The PERNETTA trial (SAKK 22/10), a randomized open label phase II study (SAKK, UNICANCER, BOOG)

Background: We assumed that a strategy with dual blockade of T+P without chemotherapy followed by T-DM1 at progression might be similarly effective in terms of overall survival (OS), but less toxic resulting in better Quality of Life (QoL) in pts with HER2+ MBC. Updated efficacy results by hormone receptor (HR) status and QoL data are given. Methods: Pts with centrally confirmed HER2+ MBC were randomized 1:1 to receive either P+T alone (arm A) or P+T combined with weekly paclitaxel or vinorelbine (arm B), followed by maintenance treatment with T+P until progression. After progression, T-DM1 was given as 2nd line therapy in both arms. The primary endpoint was OS at 24 months (mo), among secondary endpoints progression free survival (PFS) was included. QoL was assessed every 3 mo up to 24 mo during 1st line by the NFBSI-16 (summary score and subscale scores for disease-related symptoms, treatment side-effects, function/well-being). Two single items assessed treatment burden and coping. Results: Between 05/13 and 01/16, 210 pts were enrolled. Median age was 58 years, 63% of pts had lung or liver metastases, 36% of tumors were HR-, paclitaxel/vinorelbine was given in 46/59 pts. Efficacy results are shown in table. No difference in OS was observed. HR status did not affect PFS for 1st line. During 1st line, changes from baseline showed small improvements in QoL (NFBSI-16 summary scores) in arm A, while QoL scores remained stable in arm B. Patients in arm B reported more treatment burden during the first 6 months, but not thereafter, while coping improved clinically relevant in both arms. Conclusions: Despite shorter 1st line PFS, OS at 2 years was not affected for P+T alone followed by T-DM1. Side-effects were less frequently seen in the chemotherapy-free arm, although QoL was similar during 1st line in both arms. Legal entity responsible for the study: SAKK. Funding: Roche Pharma. Disclosure: J. Huober: Honorary: Roche, Novartis, Lilly, Pfizer, Celgene; Advisory boards: Roche, Novartis, Lilly, Pfizer, Celgene, AstraZeneca. B. Thürlimann: Consulting or advisory role: Roche. H. Bonnefoi: Travel grants, lecture fee: Roche. All other authors have declared no conflicts of interest.