Paclitaxel-induced apoptosis and mitotic arrest assessed by serial fine-needle aspiration: Implications for early prediction of breast cancer response to neoadjuvant treatment

The extent of tumor reduction from neoadjuvant chemotherapy for breast canc er correlates with outcome. We investigated whether the initial cellular re sponses to paclitaxel are related to the extent of tumor reduction. Eleven women with breast cancer received paclitaxel (every 2 weeks for 4 cycles) a s neoadjuvant treatment. Serial fine-needle aspirations (FNA; 25-gauge, I p ass) were obtained before treatment and at 24, 48, 72, and 96 h after the f irst paclitaxel dose, Microscopic counts of apoptotic and mitotic indices w ere performed, The change in cancer volume from treatment was determined us ing radiological measurements with allowance for change in the histopatholo gical amount of cancer, Apoptotic and mitotic responses usually subsided wi thin 4 days, The duration of the initial apoptotic response was different f or women with different treatment results. Cumulative apoptotic response fo r the first 4 days inversely correlated with the proportion of residual can cer after neoadjuvant treatment. FNA is a versatile clinical method to obta in breast cancer cells for therapy response studies, Apoptotic response to the first dose of paclitaxel is almost complete within 4 days, implying tha t more frequent (weekly) paclitaxel dosing might be beneficial, The apoptot ic respouse to the first dose of paclitaxel appeared to predict the amount of cancer reduction from this treatment, This is a promising start toward t he development of an early chemopredictive assay for paclitaxel treatment o f breast cancer.