NEW YORKA small trial of trastuzumab (Herceptin) alone and with
paclitaxel (Taxol) found that the combination was active against
prostate cancer, but trastuzumab alone was not. The results were
presented at the ASCO meeting by Michael J. Morris, MD, of Memorial
Sloan-Kettering Cancer Center.
The study included 23 prostate cancer patients (median age, 66)
stratified according to whether they were androgen dependent or
independent and whether their degree of HER2 expression was 2+ or
larger or less than 2+, as determined by immunohistochemistry using a
While trastuzumab has been shown to improve survival in patients with
HER2+ breast cancer, its effect on prostate cancer and the impact of
the degree of tumoral HER2 expression on Herceptin efficacy are
unknown, Dr. Morris said.
All patients received trastuzumab at doses of 2 mg/kg/week (IV over
30 minutes with a first-week loading dose of 4 mg/kg).
After assessment at 12 weeks, those with stable disease were to
continue with trastuzumab alone, and those with disease progression
were to cross over to trastuzumab with paclitaxel, administered at
100 mg/m² for 12 weeks, for a maximum of three cycles. At 12
weeks, however, all patients had progressed, so none continued on
Stable Disease or Better
Evaluation of the trastuzumab/paclitaxel combination showed that in
the androgen-independent group, two of four patients who were HER2
positive and four of nine who were HER2 negative had stable disease
or better, while the others progressed.
In the androgen-dependent group, the two evaluable patients who were
HER2 negative had stable disease or better.
Dr. Morris concluded, Our preliminary data suggest that
Herceptin alone has a limited role for the treatment of androgen-independent
ASCO discussant Philip Kantoff, MD, of Dana-Farber Cancer Center,
noted that HER2 overexpression appears to be unusual in primary
prostate cancer, but may be more common in metastatic disease.
Regarding the responses to the trastuzumab/paclitaxel combination in
this small study, he stated, Of course, the contribution of
Herceptin to these responses is uncertain.