A new study has reported that the likelihood of obtaining pathological complete response (no microscopic evidence of viable cancer cells in tumor specimens) as a result of pre-surgery chemotherapy depends on the cumulative dose and other factors. Pathological complete response has been shown to correlate with prognosis in breast cancer. The study included 3,332 women in seven German neoadjuvant trials.
Pathological complete response was found to be associated with (1) a greater number of chemotherapy cycles; (2) higher cumulative anthracycline dose; (3) higher cumulative taxane dose; and (4) capecitabine (Xeloda)-containing regimens. Increase in number of chemotherapy cycles was more likely to result in pathological complete response in hormone receptor positive tumors (ER+/PR+) than in hormone receptor negative tumors (ER-/PR-, including triple negative). The effect of anthracycline dose was particularly pronounced in HER2-negative tumors, compared to HER2-posiive tumors. Simultaneous treatment with Herceptin for HER2-positive tumors more than tripled the likelihood of pathological complete response. However, no association between pathological complete response and number of Herceptin cycles was found. The authors conclude that dosing appears to be important for successful treatment of breast cancer. Longer treatment, higher cumulative doses of anthracyclines and taxanes, and the addition of capecitabine and Herceptin all are associated with more favorable response. The study results also suggest that tailoring according to breast cancer phenotype might be possible: longer treatment for hormone receptor positive tumors, higher cumulative anthracycline doses for HER2-negative tumors, shorter treatment at higher cumulative doses for triple-negative tumors, and a limited number of preoperative Herceptin cycles in HER2-positive tumors.