Breast Cancer Treatments Tailored to Individuals
Advances in precision medicine are informing oncologists how best to treat patients with early-stage breast cancer, said Dr. Nancy Davidson at a recent Contemporary Clinical Medicine: Great Teachers Grand Rounds lecture in Lipsett Amphitheater.
The approach involves tailoring therapy to the characteristics of the patient and his or her tumor cells, said Davidson, president of the Seattle Cancer Care Alliance, senior vice president of Fred Hutchinson Cancer Research Center and professor of medicine at the University of Washington.
“The incidence of breast cancer is considerably higher in African-American and white women than it is in Hispanics and Pacific Islanders in this country,” she said.
There has been a decrease in mortality from breast cancer thanks to early diagnoses and advances in treatment including surgery, radiation and systemic therapies, she noted.
“The disease is largely one—although not exclusively—of older women,” Davidson explained. “The mortality from breast cancer goes up over time and is highest in older women.”
Traditionally, she said, health care professionals have determined the stage of breast cancer by measuring the size of a tumor, how many lymph nodes are involved and whether or not the cancer has spread to other parts of the body.
Starting this year, doctors began factoring biological markers into the staging system for breast cancer. When a patient first presents symptoms, an oncologist will look at results from a physical exam, any breast images and the results of biopsies and the tumor itself “including the grade and the expression of important proteins.” Final staging will be completed after definitive surgery, at which time all the pathological information will be available.
There are several molecular subtypes of breast cancer, Davidson said. One of the most common types across all ethnicities is luminal breast cancer. There are two subtypes: A and B.
Luminal A cancers are usually estrogen receptor-positive, meaning they need the hormone estrogen to grow. Additionally, they are usually HER2 receptor-negative, meaning the HER2 protein involved in cell growth isn’t found on the surface of the cancer cell. Luminal B cancers are also estrogen receptor-positive but they may be HER2 receptor-negative or positive.
Detailed information about the type of cancer helps oncologists choose the best therapy for an individual. A patient with early-stage estrogen receptor-positive breast cancer, for example, would be advised to begin what is known as endocrine therapy. The treatment slows or stops the growth of tumors by blocking a woman’s ability to produce estrogen or destroying the estrogen receptor or blocking the ability of estrogen to interact with its receptor. In some cases, patients will also receive chemotherapy.
Unfortunately, some patients don’t tolerate endocrine therapy. Hot flashes and other symptoms of menopause and other side effects such as a slight increased risk for uterine cancer or thinning of the bone may depend on the type of endocrine therapy that is used.
“These side effects are important because we are asking our patients to stay on these therapies for long periods of time,” Davidson said.
In one study of roughly 9,000 patients with breast cancer, results showed stopping the adjuvant endocrine therapy early or not taking scheduled doses was associated with increased mortality.
“The bottom line was for women who were less than 60 percent adherent; they had almost a 4-fold greater chance of dying as a consequence of breast cancer,” Davidson reported.
If a patient has HER2 proteins on the surface of a tumor, a physician would recommend both chemotherapy and one or more monoclonal antibodies against HER2 that block the function of the protein. There are five FDA-approved anti-HER2 therapies. In rare instances, some of these can be toxic to the heart.
Scientists are also studying bone-targeted treatments as a form of adjuvant therapy in older patients with breast cancer because bones are a common site of breast cancer recurrence.
Newer drug and lifestyle approaches to prevention of breast cancer recurrence are also under study.
Precision medicine will continue to drive much of the work on breast cancer that will ultimately improve patients’ lives, Davidson concluded.