Breast cancer is the most common cancer diagnosed in women globally(1). The presentation varies from mammographically detected very small tumors to metastatic cancer. The proportion of patients presenting in early, locally advanced and metastatic disease varies across the globe(2). Further, breast cancer is a heterogeneous disease with the disease biology varying from indolent hormone positive tumors to highly aggressive triple negative breast cancer (3).

In India, 30-40% of breast cancer patients present triple negative breast cancer. Such patients are treated with neoadjuvant chemotherapy . While 80-85% of breast tumors will respond to the neoadjuvant chemotherapy, pathological complete response is achieved in 25-40% of patients and varies with the subtype of breast cancer (4). The significance of pathological complete response has been extensively studied and it is well known that patients who achieve this landmark have a significantly better long term survival.

During the neoadjuvant chemotherapy, the response of tumor to chemotherapy is assessed clinically and the correlation between clinical and pathological response is poor(5). Therefore, we hypothesized that a declining trend of serum tumor markers may be able to predict the pathological response better than the clinical response and in future, the therapy may be tailored according to the decline.

We chose CA-15.3, CA 27.29, CEA, CA 125, cathepsin D as the serum tumor markers as these are the most validated markers for breast cancer(6).

Lacunae in Literature: There is very scant and sparse data on role of serum tumor markers in predicting pathological complete response in locally advanced breast cancer.

Therapeutic importance:

If we are able to predict pathological tumor response with serum tumor markers, we can personalize the chemotherapy regimens to achieve pathological complete response in a higher proportion of patients. Ultimately, this will lead to improvement of the survival outcomes of patients with breast cancer.

Rationale of the study:

In this study we propose to examine the correlation between decline of serum tumor markers (CA-15.3, CA 27.29, CEA, CA 125, cathepsin D) with neoadjuvant chemotherapy. Patients routinely have to get the bloodwork prior to every chemotherapy cycle and during this time, we will withdraw 5 ml extra blood to perform additional testing. This will be performed at four time-points:

1. Baseline

2. After 4 cycles of chemotherapy

3. At the end of chemotherapy

4. Post-surgery