last week at the San Antonio Breast Cancer Symposium, researchers announced encouraging results from studies of two cancer medications that appeared to keep breast cancer from advancing.
The first study included 808 women with advanced breast cancer. An experimental drug from Genentech called pertuzumab stalled patients' cancer for a median of 18 months when added to standard treatment, compared with a year for patients who got usual treatment alone. Whether or not it improves patients' survival isn't clear yet, but the study is ongoing. The study included women from Europe, North and South America and Asia.
Pertuzumab attacks the same target as the cancer drug Herceptin, cells that overproduce a protein known as HER2 that promotes tumor growth. Pertuzumab works in a slightly different, but complementary way, and together the drugs appear to slow down the disease. About 20% to 25% of breast cancers are positive for HER2 — these are the women who might benefit from the new pairing of drugs.
“You don't see that very often...It's a spectacular result,” said one study leader, Dr. Sandra Swain, medical director of Washington Hospital Center's cancer institute. “Pertuzumab is a winner,” Dr. Eric Winer of the Dana Farber Cancer Center told the Associated Press. Winer was not affiliated with the study.
The most common side effects of pertuzumab were diarrhea, rash and low white blood cell counts, which often occur with cancer treatment. Among the 402 women given pertuzumab in addition to Herceptin and chemotherapy, 69 died - compared with 96 deaths among the 406 women given Herceptin and chemo alone. The dual treatment did not cause more heart problems - an issue with other Herceptin combinations. “We're really pleased that there were no new safety signals” and that pertuzumab is so promising, said Dr. Sandra Horning, Genentech's global development chief of cancer drugs.
The second clinical trial involved Novartis AG's drug everolimus (Afinitor), which is normally used to suppress the immune system of organ transplant patients. Researchers coupled the drug with an aromatase inhibitor in a trial of 724 women, and the combo slowed progression of metastatic breast cancer by four months, compared with the aromatase inhibitors alone. Overall, women getting everolimus had seven months with no disease progression, compared with three in the group that did not get the drug.
“These results establish a new standard of care for this group of patients,” Dr. Gabriel Hortobagyi, professor of medicine at MD Anderson Cancer Center in Houston and lead author of the study, which was presented at the conference and published in the New England Journal of Medicine, told Medpage Today.
The combo of Afinitor and hormone-blocking drugs did lead to more side effects - mouth sores, anemia, shortness of breath, high blood sugar, fatigue and lung inflammation. But “the two together have a much greater effect than you would expect from either alone,” said study leader Hortobagyi. “They snip two wires that are critical” for growth signals to continue, he said.
Because neither drug combination is yet approved by the Food and Drug Administration for use in treating breast cancer, and pertuzumab is still experimental, additional studies will need to validate the results and show that the drugs can extend survival of patients longer than those that are currently available. Additionally the drugs are likely to be very expensive, up to $10,000 a month, the AP reports.
Regarding the everolimus trial, Dr. Vered Stearns, the co-director of the Breast Cancer Program at Johns Hopkins University, told Medpage Today, “The superiority of the combination is statistically and clinically significant and I anticipate that will lead to approval and clinical use within a year or less.” “These are powerful advances ... an important step forward,” said Dr. Harold Burstein, a breast expert at Dana-Farber Cancer Institute in Boston who had no role in the studies.
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