As scientists unravel further how breast cancer develops, evades treatment and spreads, they are finding better and finer targets for drugs that attack the machinery of cancer.
In Augusta, several different approaches are being taken using drugs that have potentially fewer side effects for healthy tissue. At Augusta Oncology Associates, Dr. Mark Keaton is part of a national trial looking at a drug called a PARP inhibitor. PARP, or Poly ADP-Ribose Polymerase, is an enzyme used in DNA repair, Keaton said. The drug seems to work best in those who have a BRCA gene mutation, a risk factor for inherited breast cancer, which means they already have impaired DNA repair.
"If they have the BRCA mutation, that's how they're repairing their DNA is with the PARP enzyme," Keaton said." If you inhibit that, then they really are especially susceptible to the chemotherapy drug," which damages the DNA of cancer cells.
The current trial is in those who are considered to have "triple negative" breast cancer, in that their cancer cells lack receptors for estrogen, progesterone and human epidermal growth factor 2 or HER2/neu. Those cancers are considered to have a poorer prognosis because they are not sensitive to hormonal therapies or more targeted drugs.
Triple negative cancers are also a focus for Medical College of Georgia Cancer Center because of its patient population, said Dr. Thomas Samuel, director of the Multidisciplinary Breast Cancer Program.
"African Americans are more prone to develop triple negative breast cancer," he said. "And because of that, because we have a large African American population, that's an area that we're really looking at."
In one clinical trial, MCG is testing a drug called XL 184, which is a multitargeted tryrosine kinase inhibitor. It targets pathways inside the working of the cells by which the tumor might create new blood vessels to feed itself, called angiogenesis.
Breast cancer, because its research is better funded than other cancers, has been making these kinds of breakthroughs, which are slowly being adopted for other types of cancer, he said.
"Breast cancer has always been in the forefront because it is in the public eye; it is in the public concern," Samuel said. "But now the pathway by which breast cancers are being treated is being recreated in other cancers."
Both Keaton and Samuel see even more targeted therapy in the future.
"I think it will hopefully eventually come to tailored medicine," Keaton said. "In other words, if you get a malignancy, your treatment will be tailored to treat your malignancy rather than a treatment used to treat all of the cancers. Of course, the PARP inhibitors are taking that approach."
Samuel said that one day tumor samples could go into a machine that would perform genetic and epigenetic testing on the sample.
"And then on the other side spits out, 'This is what this patient should receive; these are the drugs that are most likely to work; this a tumor that radiation might be most beneficial to or might have the greatest effect,' " he said. "We're not that far off."