By Duke Medicine News and Communications
DURHAM, N.C. -- A new and experimental breast cancer drug
called lapatinib inhibited tumor growth in nearly half of women
who took it for eight weeks in a national Phase I clinical
trial, according to results of a study being presented at the
annual American Society of
Clinical Oncology meeting in New Orleans.
Kimberly Blackwell, M.D., an oncologist from the Duke Comprehensive Cancer Center,
presented data showing that 46 percent of breast cancer
patients who took the oral drug for eight weeks had stable
disease or tumor shrinkage. Approximately 24 percent of
patients who took the drug for four months had stable disease
or tumor shrinkage.
The results are quite encouraging, said Blackwell, because
lapatinib is one of the first drugs to elicit a response in
women whose tumors did not respond to at least two traditional
therapies, including trastuzumab (Herceptin).
Trastuzumab is the front-line drug used to treat women whose
tumors overproduce a growth-regulating protein called Her-2.
Trastuzumab blocks the Her-2 receptor on cancer cells and
inhibits its signaling, thereby shrinking or stabilizing the
tumor.
But nearly one-third of tumors with Her-2 over-expression do
not respond to trastuzumab, said Blackwell. In the current
trial, the majority of patients -- 59 percent -- had progressed
through three, four or five traditional cancer drugs.
Lapatinib represents a new type of therapy because it
targets Her-2 plus another growth factor protein called
Epidermal Growth Factor (EGFR). "Blocking the action of two
growth factors has a more profound effect on inhibiting cell
growth than blocking a single growth factor, and we think this
dual action on breast cancer cells is responsible for the
positive effects we're seeing," said Blackwell. The study was
funded by GlaxoSmithKline, the maker of lapatinib.
The study showed that lapatinib was safe and had minimal
side effects, because it targets only these two very specific
receptor sites on breast cancer cells, said Blackwell. Five
percent of women experienced a rash, 5 percent had fatigue, and
10 percent had diarrhea. In contrast, chemotherapy can cause
debilitating nausea, anemia, fatigue and the potential for
heart and liver damage.
The trial is continuing to recruit patients at Duke and
other sites around the country.
