Uncontrolled growth of ovarian cancer cells is the fifth leading cause of female cancer deaths since most ovarian cancer patients are diagnosed at an advanced stage of metastatic disease. Here, we report on the sensor for monitoring the cancer treatment efficiency in real-time. We measure the optical interaction between the evanescent fields of microfiber and ovarian cancer inter-cellular medium at different treatment stages. Spectral absorption signatures are correlated with optical micrographs and western blot tests. We found that the treatment of tumor cells with induces both cells growth arrest and alter the spectral lines in a dose-dependent manner. These observations are mediated by surface roughness out of silica glass material, form an essential step toward the development of early detection of response to cancer therapy.