Is Tykerb for You? Reading Research to Make Medical Decisions

When Sarah Park, our producer here at HealthCentral, asked me if I would be interested in writing a post about a trial of lapatinib (trade name Tykerb in the US and Tyverb in Europe) for inflammatory breast cancer (IBC) patients, I jumped at the chance.  I’ve been reading about this drug for several years now on the mailing list at www.ibcsupport.org and wanted to know more.  I started my research for this post by reading the article Sarah linked me to from EurekAlert.org about a trial done by Dr. Stephen Johnston and Dr. Bella Kaufman for 126 IBC patients.

To begin with I was really impressed.  I remember how hard it was to get data on the best treatments for me eleven years ago.  Because IBC is a comparatively rare form of breast cancer, there have been few studies exclusively for IBC patients.  Some studies even exclude IBC patients.  So this study will give IBC-specific information for patients and doctors trying to decide whether to try lapatinib.

I quickly realized that I needed to understand more about how lapatinib works, so I checked out some other sites.  The FDA approved the drug in March 2007, and their press release at the time gave the best explanation for a layperson that I found.  The release compares how Tykerb and Herceptin (trastuzumab) work. “Tykerb, a new molecular entity (NME), is a kinase inhibitor working through multiple pathways (targets) to deprive tumor cells of signals needed to grow. Unlike, for example, trastuzumab — a monoclonal antibody, which is a large protein molecule that targets the part of the HER2 protein on the outside of the cell — Tykerb is a small molecule that enters the cell and blocks the function of this and other proteins. Because of this difference in mechanism of action, Tykerb works in some HER2 positive breast cancers that have been treated with trastuzumab and are no longer benefiting.”

So far lapatinib has been approved just for metastatic breast cancer patients who did not get a good response from Herceptin.  It is administered along with Xeloda. 

Armed with more background information, I reread the summary of the Johnston/Kaufman study.  In this study none of the 126 patients showed a “complete response” to the treatment.  The best it could do was slow down the cancer.  Thirty-nine percent of the patients showed a fifty percent decrease in their disease for a median duration of response of 21 weeks.

The study evaluated the median overall survival for four categories of patients:

1.  Responded to lapatinib and had previous Herceptin:  18.4 months

2.  Responded to lapatinib and no previous Herceptin:  14 months

3.  Unresponsive to laptininb, and had previous Herceptin:  8.4 months

4.  Unresponsive to laptininb, and no previous Herceptin:  8.2 months

My initial reaction was that these figures are not very impressive.  Then I read the original study in The Lancet.  I won’t pretend to say I can read a medical journal article and understand it all, but when I saw the tables in the original article, I realized that the vast majority of the women in the study were not only already Stage IV, but had not responded well to chemotherapy or to Herceptin.  For those women, 18 extra months are significant.  A before and after picture of a woman's breast with a "partial response" also helped me understand how important even a partial response would be for a metastatic patient.