A research study shows patients with advanced breast cancer tied to an inherited gene mutation treated with an experimental Pfizer Inc drug went about three months longer before their disease worsened.
New research suggests that a blood test five years after breast cancer treatment may help identify some women who are likely to relapse, long before a lump or other signs appear.
The findings are considered preliminary, and more research is needed to determine whether and which women may benefit from these tests.
They're called liquid biopsies, and they look for stray cancer cells that tumours can shed into the blood. The tests are sometimes used now to monitor patients with advanced cancer during treatment.
This was the largest study for predicting relapses in women with breast cancers that are fuelled by estrogen, the most common form of the disease.
Results were discussed on Friday at the San Antonio Breast Cancer Symposium.
Experimental drug for BRCA gene mutation
Patients with advanced breast cancer tied to an inherited gene mutation who were treated with an experimental Pfizer Inc drug went about three months longer before their disease worsened than those who received chemotherapy in a late-stage study, according to data released on Friday.
The drug, talazoparib, a once-daily pill that Pfizer acquired with its $14 billion purchase of Medivation, belongs to a class of medicines called PARP inhibitors that may induce tumour cell death. They have shown promise in advanced ovarian and breast cancers.
Patients in the Phase III study had mutations of the BRCA1/2 genes, the type of mutation that led actress Angelina Jolie to have preventive breast removal surgery.
About three percent of breast cancers occur in people with inherited BRCA1 or BRCA2 mutations that lower a cell's ability to repair damaged DNA. Up to 65 percent of women who inherit the mutations will develop breast cancer, often much younger than is typical for the disease.
In the 431-patient trial, those who received talazoparib went 8.6 months before half of them experienced disease progression, a measure known as median progression-free survival (PFS). Among those who received standard chemotherapy, the median PFS was 5.6 months.
Complete or partial response
In addition, 62.6 percent of talazoparib patients experienced a complete or partial response to the treatment compared with a 27.2 percent response rate for chemotherapy.
At least 12 patients who received the Pfizer drug, or 5.5 percent, had a complete response, meaning no detectable sign of cancer. There were no complete responses in the chemotherapy group. The results, unveiled at the symposium, were highly statistically significant.
Researchers also reported a significant delay in time to meaningful deterioration of quality of life among talazoparib patients.
Dr Jennifer Litton, the study's lead investigator from MD Anderson Cancer Center, said there are currently no drugs specifically approved for this group of patients aside from standard chemotherapy courses.
The results were consistent whether patient had received up to three courses of chemotherapy or none at all, or whether patients' cancers had spread to the brain.
The incidence of serious adverse side effects was similar in both groups – 31.8 percent for the Pfizer drug and 29.4 percent for chemotherapy. Discontinuations due to adverse events occurred in 7.7 percent of talazoparib patients and 9.5 percent in the chemotherapy group.