Under the microscope: Individualized therapy for breast cancer

Recently, some of the “biggest” advances in the treatment of breast cancer have, in fact, been very “small.” By identifying DNA sequences or proteins that may be produced in much higher volume in patients with cancer, specialists can now incorporate therapies that target cancer at its molecular source.

“Oncologists are now able to interrupt many specific cellular processes that cause cancer tumors to grow,” said Rabia Mir, M.D., chair of pathology and laboratory medicine at New York Methodist Hospital. “This is done using small molecules that target specific genetic alterations of a tumor. These targeted cancer therapies are often used in conjunction with other treatments, such as radiotherapy, chemotherapy and surgery.”

Molecular targeting has been valuable in treating particularly aggressive breast cancer cases, such as those caused by mutations in the HER2 protein receptors, which are found on the surface of breast cells.

One out of every four breast cancer diagnoses has been found to involve a malfunction in the HER2 gene, which can result in the uncontrolled multiplication (overexpression) of breast cells, leading to tumor growth and eventual metastasis (spread). Through a standard tissue biopsy, laboratory tests can now determine whether or not a patient’s breast cancer might be the result of HER2 overexpression, and treatments are available specifically for this form of the disease.

“We can perform a number of laboratory procedures that can help to determine the molecular makeup of a patient’s cancer,” said Mir. “For example, a laboratory preparation called immunohistochemistry can often allow us to determine if there is an overexpression of the HER2 protein.

“If a HER2 mutation has been identified, clinical oncologists can incorporate specific drugs into a patient’s treatment regimen to inhibit HER2 function, which may help slow or stop the growth of that patient’s cancer,” Mir continued. “And if a patient is found not to have the HER mutation, tests can be performed for other genetic abnormalities, such as an estrogen receptor (ER) mutation or a progesterone receptor (PR) mutation, and a different therapy may be used for those.”

With today’s diagnostic tools, pathologists can analyze cancerous tissue at every stage, from initial diagnosis through biopsy and surgery, to determine the least disruptive and most appropriate course of treatment for each patient.

Organ-by-organ, gene-by-gene molecular evaluation and treatment are at the core of personalized cancer therapy, and sometimes, the “next big thing” in cancer treatment can only be seen with a microscope.

For an appointment for breast cancer services at New York Methodist Hospital, call 718-246-8500.