The media are abuzz today about the FDA's approval of the new breast cancer drug Tykerb, also known by its generic name, lapatinib.
Reporters are asking how important this new targeted therapy really is and what its impact will be on the treatment of women with breast cancer.
The answers to these questions are fairly straightforward, but the impact over time is a bit more uncertain.
Breast cancer is not one single disease.
When breast cancer is diagnosed, doctors examine the cancer specimen for several different markers that give us clues as to how the cancer will behave -- and what treatments may be helpful in preventing its recurrence. These tests also provide clues to what treatments may be most effective if the breast cancer relapses.
For many years, we have measured hormone receptors (estrogen and progesterone) in the breast cancer tissue, and more recently doctors have looked for another genetic marker called HER2.
When this HER2 marker is present in the cancer tissue (as is the case in approximately 20 percent of the estimated 178,480 invasive breast cancers that will be diagnosed in women in the United States in 2007), it signals a cancer that is usually more aggressive than the typical breast cancer. It also usually occurs in a younger population.
Herceptin, also known by its generic name, trastuzumab, is a drug that targeted this abnormality in breast cancer tissue. When it was first approved by the Food and Drug Administration in 1998, it represented a significant step forward in the treatment of advanced breast cancer in women who had this particular genetic marker.
Trastuzumab improved response rates and lengthened survivals for many women who had found themselves in a grim situation. It wasn't a cure, but it was a major step forward.
It represented not only an effective cancer therapy but also proof that targeted therapies could be very helpful in the treatment of a variety of cancers.
More recently, in 2005, research was presented at a major cancer meeting and then published in the New England Journal of Medicine that trastuzumab was very effective when used in the adjuvant treatment -- the therapy that follows primary treatments like surgery and radiation -- when breast cancer patients were HER2 positive.
These studies demonstrated that trastuzumab, as part of a regimen of adjuvant chemotherapy, decreased recurrences and decreased deaths in women with breast cancer who were HER2 positive at the time of initial diagnosis.
The impact of these reports was dramatic. They literally changed the standard of care for breast cancer treatment overnight in the United States and elsewhere.
But for those women who could not tolerate trastuzumab, or whose disease progressed after taking this intravenous drug, there have been few effective options and certainly no new targeted therapies that honed in on the particular genetic marker in question.
That's where lapatinib fits in, and that is why there is so much excitement.
Lapatinib is a drug that is taken orally, and it works in the same women who are candidates for trastuzumab -- namely, those who are HER2 positive.