Neoadjuvant chemotherapy (NAC) is usually used to facilitate breast-conserving surgery and improve surgical outcomes for breast cancer patients \[1\]. In addition, NAC can help to eradicate micrometastatic disease and serve to test chemosensitivity while providing similar survival benefits to adjuvant chemotherapy \[2-5\] .
Pathologic complete response (pCR) after neoadjuvant chemotherapy is associated with superior survival outcomes, with higher rates of pCR in human epidermal growth factor receptor 2 positive (HER2+) and triple negative breast cancer (TNBC) subtypes compared to hormone receptor (HR)-positive subtypes \[6-7\] .
Patients who achieve pCR also remain at signifcant risk of relapse, with studies reporting 5-year disease-free survival (DFS) rates of 75-87% \[2,8-10\] . Retrospective study of 88 Japanese patients who achieved pCR reported a recurrence rate of 13.6% and all relapses occurred within 32 months from diagnosis \[11\].
There for, little is known about the patterns of relapse after NAC especially in the real world. There are currently no specific guidelines for post-treatment follow-up of patients treated with NAC and variations in practice exist. So, this study aims to evaluate the relapse risks in different subgroups of breast cancers treated with NAC and determine the associated time trends and patterns of relapse in these patients. These findings may potentially lead to the development of risk-adapted surveillance strategies for patients treated with NAC
