By Jennifer Litton, M.D.
Today at the 2010 ASCO Annual Meeting, a number of studies were presented regarding metastatic breast cancer. Several looked at new drugs showing promise in women with HER2 positive breast cancer who have already had trastuzumab and/or lapatinib therapy.
Trastuzumab DM-1 is a new therapy combining trastuzumab with another toxin that now gets taken up by the metastatic tumor and releases a toxin that kills the tumor cell. The biggest side effect of this therapy appears to be low platelets. Additionally, studies presented look at pairing it with pertuzumab, another anti-HER-2 agent that may also target resistance to trastuzumab. Two other studies looked at adding everolimus, an mTOR inhibitor to trastuzumab. The idea is to block a mechanism of resistance to trastuzumab.In the research presented by Morrow and Esteva, et al., this combination of everolimus and trastuzumab had 47 patients. Fifteen percent of patients had a partial response and 19% had stable disease for >/= 24 weeks in women who had already received trastuzumab showing biological activity of this combination.