Ten years of using adjuvant trastuzumab in breast cancer in Serbia - Single institution experience.

Purpose: The purpose of this study was to determinate disease-free interval (DFI) and overall survival (OS) in HER2-positive breast cancer patients who received adjuvant trastuzumab at the University Clinic of Nis, Serbia, and to investigate the influence of clinicopathological and biological characteristics of the tumor on prognosis. The second aim was to determinate the most frequent cause for the treatment discontinuation, recurrence rate, as well as the site of most common localization of the first recurrence of disease.

Methods: This research was conducted as a retrospective study at the University Oncology Clinic, Clinical Centre in Nis. The study included 238 patients who were operated and treated for HER2-positive breast cancer between January 1st, 2007 to September 30th, 2012 and followed up until December 31st, 2016. Trastuzumab was administered concurrently with taxanes, if administered, or after the completed anthracycline-based chemotherapy.

Results: After a median follow up of 69 months the 5-year DFI was 65.9% and 5-year OS was 81.8% and, as expected, significantly longer in the group of patients with smaller tumors, a smaller number of positive axillary lymph nodes, as well as a lower stage of disease (p<0.0001). Patients older than 65 years had a longer DFI compared to the 45-65 and under 45 age groups of patients (p=0.01). No statistical significance was found in the length of DFI in relation to the histological tumor subtype, tumor grade, or the status of hormone receptors. Unlike DFI, a longer OS was recorded in the group of patients with lower tumor grade (p=0.03) and there was no statistically significant difference in survival regarding the age of patients (p=0.07). Recurrence occurred in approximately one third of the patients (38.23%), mostly in the form of local recurrence. Adjuvant therapy with trastuzumab was not completely carried out in 18.49% of the patients, the most common reason being the progression of disease.

Conclusions: A long median follow up period of 69 months indicated that anti-HER2 monoclonal antibody trastuzumab, after anthracycline-based chemotherapy or concurrently with taxanes, is efficient and safe in treating early breast cancer.