Sept. 14 (HealthDay News) -- New research suggests that the anti-breast cancer drug trastuzumab, also known as Herceptin, isn't reaching its full potential. Many patients aren't receiving tests that determine whether it's appropriate or are taking it when they don't need to.

Under current guidelines, women with breast cancer in its early stages should receive tests to see if Herceptin might be appropriate for them.

In the new study, researchers analyzed medical data to see if testing has become routine. Their findings will appear in the Nov. 15 issue of the journal Cancer.

As many as two-thirds of patients who were eligible for the testing didn't appear to have had it. And about 20 percent of those who did take the drug appeared to have not taken the test to see if it could work for them in the first place, the researchers found.

In another complication, the research suggests that about one in five tests is inaccurate.

Filling the gaps in care "may help optimize limited health-care resources and improve care for women with breast cancer," said study co-author Dr. Elena Elkin, a researcher at Memorial Sloan-Kettering Cancer Center in New York, in a news release from the journal's publisher.

Doctors are increasingly trying to fine-tune treatments so they specifically target the disease in a particular patient, the researchers noted.

SOURCE: Cancer, news release, Sept. 14, 2009