In a study and editorial reported in the New England Journal of Medicine in December 2006, researchers reported the results of a clinical trial in which women with breast cancer who were HER2 positive and had failed treatment with intensive chemotherapy and trastuzumab were randomly assigned to be treated either with another chemotherapy drug as a single agent, or with the same chemotherapy drug along with the addition of lapatinib.
The results in this study of 324 women showed that, in the women who had received chemotherapy plus lapatinib, the time it took for the cancer to resume its advance after starting the new treatment was 8.4 months on average.
For the women who received just the chemotherapy without lapatinib, the time to disease progression was 4.4 months.
In other words, the women who received the additional new targeted therapy had their disease remain at least stable for almost twice as long as the women who received only chemotherapy.
Unfortunately -- and this is an important observation -- the overall survival for both groups, whether treated with chemotherapy alone or chemotherapy with the addition of the targeted therapy, was equivalent.
So what does this mean? Is this really a great new breakthrough in the treatment of breast cancer? Where does it fit today in the treatment of breast cancer, and what are lapatinib's future prospects?
Today, the answers to these questions are fairly straightforward. But interestingly, the answers may be more difficult as time goes on and we learn more about the benefits, risks and effectiveness of both lapatinib and trastuzumab.
First, is this a great breakthrough?
Yes, and no.
Yes, it is a significant step forward because it once again demonstrates the promise of targeted therapies, where we take our understanding of how cancer cells work and apply that knowledge to new drug development.
Yes, because we now have a new drug that offers promise and hope to women who have a more aggressive form of breast cancer, where until very recently we had little to offer. Now, we have two drugs that are effective in treating this particular form of the disease.
Will this change the way we treat breast cancer patients today?
For the most part, no. Women who have surgery or recurrence of their disease will still be tested for HER2. If they are positive for the marker and are candidates for trastuzumab, they will still most likely (and appropriately) receive trastuzumab as their first-line choice of treatment.
I do not see lapatinib being used today in the adjuvant therapy of breast cancer, except perhaps in those women who cannot tolerate trastuzumab.
We need to remember that lapatinib was tested only in women with advanced and progressing breast cancer where other treatments -- including chemotherapy and trastuzumab -- had been tried and failed. So, these were the types of situations in which any response was welcome news, even if it didn't prolong survival.
Over time, I have no doubt that studies will be done to look at lapatinib's effectiveness earlier in the treatment of breast cancer, such as at the time of first recurrence and possibly even in a head-to-head comparison with trastuzumab.
There may even come a time when both drugs will be used together to find out if the combination is more effective than either drug alone.