Adding the advanced prostate cancer drug Zytiga to hormone therapy before surgery has been shown for the first time to eradicate tumours in some men with high-risk forms of the disease, medical experts said.
The mid-stage trial found that six months of treatment with the combination therapy completely or nearly eliminated the cancer in a third of patients, all of whom had localised, aggressive cancer.
"These results are very impressive, especially given these high-risk patients," Dr Mary-Ellen Taplin, associate professor of Medicine at Harvard Medical School and the study's lead author, said at a news conference.
Zytiga, made by Johnson & Johnson, is already approved to treat advanced prostate cancer in patients who previously received chemotherapy. J&J expects to file in the second half of this year for US regulatory approval of the drug as a treatment for men with metastatic prostate cancer who have not yet received chemotherapy.
Cancer spreads to other parts
Zytiga, also known as abiraterone, costs about R41 000 a month. It is a member of a new drug class designed to work inside cancer cells to block production of testosterone, the male hormone that fuels prostate cancer cell growth.
Localised high-risk disease is defined as prostate cancer in men with high levels of prostate-specific antigen and aggressive disease that has spread throughout the prostate.
Men with this stage of disease tend to have a poor prognosis, and the cancer often spreads to other parts of the body despite aggressive treatment with available therapies, according to the American Society of Clinical Oncology, which featured the Zytiga data ahead of its annual meeting.
"Theoretically ... when you get a complete disappearance of the primary cancer, patient outcomes are much better," said oncologist Dr Nicholas Vogelzang, chair of ASCO's cancer communications committee, who was not involved in the research. He noted that such pre-surgery treatment has become standard care for other types of cancer.
Therapy tolerated by groups
The Phase 2 trial looked at the effect of adding Zytiga to Lupron, a drug designed to trick the testicles into ceasing production of testosterone.
Of the 29 men who received the drugs for six months before having prostate surgery, the prostates of three had no evidence of cancer and seven had nearly complete elimination of the disease. In the group of men treated for three months before their surgery, 15% had little to no detectable cancer in the prostate.
Researchers said the therapy was well-tolerated by both groups. They reported five cases of elevated liver enzymes and three patients with lower-than-normal levels of potassium.
"Our findings suggest that this combination therapy approach could improve outcomes for a substantial number of men," Taplin said. "This is a 58-patient trial with a very, very expensive drug, so I don't think anybody is going to be encouraging this type of treatment without more data."
She said other trials are under way, including a similar trial combining Zytiga with experimental drug ARN-509, which is being developed by Aragon Pharmaceuticals.
(Sapa, May 2012)