Biomarkers Help Patients Make Better Medical Decisions

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

"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.

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