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Biomarkers Help Patients Make Better Medical Decisions

The information gleaned from cancer biomarkers can be both a treasure chest and a Pandora’s box.

BY LAURA BEIL
PUBLISHED THURSDAY, MARCH 6, 2014
"How is this even possible?” she recalls asking. As a project coordinator at the American Cancer Society’s headquarters in Atlanta, she quickly devoured every bit of information at her fingertips. “When your doctor says, ‘You have breast cancer,’ your world stops,” she says. She was relieved to know that her cancer was highly treatable. But the presence of the BRCA mutation meant that her cancer was not an unlucky fluke, but a threat programmed into her cells.

Tricia Jeffers wasn't as worried about the cancer she had as she was about the one she didn't have. During her annual checkup last year, her doctor found two lumps in her right breast. He was confident that one was a cyst. The other gave him pause, however, and a biopsy soon confirmed his suspicions. Jeffers, 41, and the mother of an 11-year-old son, had an early-stage malignancy. As part of the diagnosis and because of her young age, her doctor ordered a laundry list of genetic tests on her tumor and blood. None of her relatives had ever had breast cancer, so Jeffers was shocked when results confirmed she had inherited a genetic mutation of the BRCA2 gene that increased her risk of developing breast, ovarian and other types of cancer.

This kind of harbinger was unknown a generation ago. Yet, cancer care is heading in a new direction, as patients and their doctors are increasingly able to make treatment decisions based in large part on a cancer’s invisible biochemical clues. These bits of information, called biomarkers, only a few of which are inherited, are helping patients better understand the highly individualized risks and benefits of certain treatments.

For Jeffers, harboring an inherited BRCA2 mutation led her to decide to undergo a double mastectomy. “I didn’t want to have to go through cancer twice,” she says. “I wanted it over and done with.” Other difficult choices await: She knows she has a high risk of developing ovarian cancer, too, but is not yet ready to part with her ovaries.

This complexity is one reason the discovery of cancer biomarkers can be both a treasure chest and a Pandora’s box. There was a time when a cancer’s molecular secrets were largely a mystery, so doctors relied on the information they had in front of them to recommend treatment: How advanced was the cancer? What did it look like under a microscope? What type of tissue did it come from? But with the revolution in gene-hunting technology—enabling doctors to find genetic changes at astonishing speed—patients can make medical decisions based on the biochemical changes no one can see.

A cell’s genes contain the instructions for making all the molecules that keep life going. Cancer occurs when these instructions go haywire, allowing cells to grow with abandon. It is as if a car’s brakes fail (loss of tumor suppressor genes), or the accelerator pedal is stuck (expression of oncogenes). Some genetic flaws are inherited, others develop only in the tumor, and sometimes the genetic instructions themselves work fine, but other molecular changes keep them from turning off or on. Taken as a whole, the genetics of a cell largely control when it becomes cancerous, how fast it will grow, how hard it will be to treat, and how likely it might be to return after treatment.

The goal of testing for biomarkers is to use information about a tumor’s surface markers or genetic makeup to tailor treatment to a patient’s cancer, because one person’s breast cancer or colon cancer is probably not the same as another’s. Some doctors believe the day is coming when even the lexicon of cancer could change—instead of talking about cancer in terms of the organ or tissue from which it originates, doctors will classify cancers based on the biochemical changes hiding within.

Still, biomarker research has a long way to go. Moreover, knowing about a biomarker is only part of the decision-making equation. Doctors are keenly aware that they don’t treat just the cancer, they treat individual patients—each with different values, different hopes and different desires for the future.

[Read Taking it Personally]

In an ideal world, each person’s treatment would be exquisitely aligned with the genetic alterations that gave rise to the cancer. This isn’t yet possible, sometimes because the flaws aren’t known and sometimes because medical science doesn’t yet have drugs to address them. This means that doctors sometimes have to recommend treatments without the guidance they would like. “We still treat a lot of people who don’t need chemotherapy,” says John Marshall, chief of the division of hematology and oncology at Georgetown Lombardi Comprehensive Cancer Center in Washington, D.C.

The idea of treating cancer according to its biologic behavior is not new. The drug tamoxifen, used to treat cancers driven by estrogen, has been around for decades. But now doctors have even more insight, especially for certain cancers. “Breast cancer has led the field,” says Don S. Dizon, who specializes in treating women’s cancers at the Massachusetts General Hospital Cancer Center in Boston.

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