Among women with surgically removed, high-risk HER-2/neu-positive breast cancer, trastuzumab has demonstrated significant improvements in disease-free and overall survival. The objective of this study is to evaluate the cost-effectiveness of the currently recommended 12-month adjuvant protocol of trastuzumab using a Markov modeling approach and real-world cost data.

Abstract Background Recent studies have shown that breast cancer subtype can change from the primary tumour to the recurrence. Discordance between primary and recurrent breast cancer has implications for further treatment and ultimately prognosis. The aim of the study was to determine the rate of change between primary and recurrence of breast cancer and to assess the impact of these changes on survival and potential treatment options. Methods Patient demographics were collected on those who underwent surgery for breast cancer between 2001 and 2014 and had a recurrence with biopsy results and pathology scoring of both the primary and recurrence. Results One hundred thirty two consecutive patients were included. There were 31 (23.5%) changes in subtype. Discordance occurred most frequently in luminal A breast cancer (n = 20), followed by triple negative (n = 4), luminal B (n = 3) and HER2 (n = 3). Patients who changed from luminal A to triple negative (n = 18) had a significantly worse post-recurrence survival (p < 0.05) with overall survival approaching significance (p = 0.064) compared to concordant luminal A cases (n = 46). Overall receptor discordance rates were: estrogen receptor 20.4% (n = 27), progesterone receptor 37.7% (n = 50) and HER2 3% (n = 4). Loss of estrogen receptor and progesterone receptor was more common than gain (21 vs. 6 (p = 0.04) and 44 vs. 6 (p = 0.01) respectively). Nine patients (6.8%) gained receptor status potentially impacting treatment options. Conclusion Discordance in subtype and receptor status occurs between primary and recurrent breast cancer, ultimately affecting survival and potentially impacting treatment options.