Effects of delayed initiation of adjuvant trastuzumab for non-metastatic, HER2 positive breast cancer in a limited resources setting: ML25232 study final results

Abstract Background An optimal adjuvant treatment of HER2 positive breast cancer includes the initiation of trastuzumab within 6 months after the surgery. However, due to limited resources and waiting lists, this timeframe is often exceeded in developing countries. We previously reported short-term outcomes of a time-optimal versus delayed postoperative initiation of trastuzumab in women with HER2 positive, non-metastatic, neoadjuvant naive breast cancer. Here, we report an extended follow-up, summarizing outcomes of our cohorts. Methods We included 223 consecutive women with surgically treated, non-metastatic, neoadjuvant naive, HER2 positive breast cancer from 2009 to 2011, from four institutions in Bosnia and Herzegovina. Patients were assigned to a time-optimal group (TOG), or a delayed group 1 (DG1), or a delayed group 2 (DG2), depending on whether their adjuvant trastuzumab was initiated 6 months, or 6-12 months, or more than 12 months after the surgery, respectively. A cut-off point for the follow-up was January 2019. We compared clinical outcomes between the groups, taking into account lymph node status. Results The patient’s median age was 55 (range 27-80) years. Mean follow-up period was 67 (range 4-109) months. Node-negative disease was found in 38.6% patients overall. 37% (TOG) patients received trastuzumab within 6 months, while 41% (DG1) received it within 6-12, and 22% (DG2) more than 12 months after their surgery. A higher number of node negative patients was found in the DG2 group compared to the TOG and DG1 groups (48%, 35%, and 36% respectively). 5-year DFS rate was 70.73% (TOG), 67.03% (DG1), and 62.00% (DG2). The OS rate was 78.05% (TOG), 75.82% (DG1), and 74.00% (DG2). Conclusions From the above, a conclusion can be made that patients with time-optimal initiation of adjuvant trastuzumab therapy had a higher 5-year DFS and OS rate compared to the delayed treatment initiation groups. Results of the DG1 and the DG2 group indicate that trastuzumab therapy shows a persistent benefit even if administered with a delay. Higher DFS and OS rates in the DG2 group could be explained by a higher number of node-negative low-risk, patients in this group. Legal entity responsible for the study The authors. Funding Roche. Disclosure S. Beslija: Advisory / Consultancy, Research grant / Funding (self), Travel / Accommodation / Expenses: Roche; Advisory / Consultancy: Novartis; Advisory / Consultancy: MSD; Advisory / Consultancy, Travel / Accommodation / Expenses: Pfizer. T. Ceric: Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche; Advisory / Consultancy: MSD; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Novartis. B. Hasanbegovic: Advisory / Consultancy: Roche. A. Pasic: Advisory / Consultancy: Merck; Advisory / Consultancy: Sanofi. All other authors have declared no conflicts of interest.