In 2005, after she had spent more than a year going from specialist to specialist, a dermatologist figured it out. Mrs. McDaniel, then 62, had Sezary syndrome, a rare T cell lymphoma, in which white blood cells become cancerous and migrate to the skin. All her doctors could tell her was that the disease was incurable, that there was no standard treatment, and that on average patients at her stage die within a few years.

“Of course I was shocked,” Mrs. McDaniel said in an interview last September.

She wept that day as her husband drove her home. And she asked God to help her cope.

Before cancer, she had had a vibrant life, hiking in the mountains, traveling the world, entertaining her wide network of friends. Her disease destroyed all of that. She could not even enjoy her luxuriant garden because sun on her inflamed skin was agony.

Although there is no standard treatment, for five years chemotherapy held her disease at bay. But in the summer of 2010, she got worse, much worse, with hundreds of tumors popping up under her skin. Some grew as large as kiwi fruits and split open.

Her son, Dr. McDaniel, decided he would orchestrate the use of the most advanced techniques of gene sequencing and analysis to take on her cancer. Because of his job — he works for Illumina, a company that does DNA sequencing — Dr. McDaniel had read scientific reports and gone to medical conferences where he heard talks on whole genome sequencing. He noticed that the patients all seemed to have rare cancers.

“Every time I heard one of those stories, I thought, ‘That’s my mom,’ ” he said.

For now, there are not many drugs that can target specific gene mutations in cancer cells.

But the hope is that when more is known and more drugs are developed, doctors will treat cancer by blocking several major genes at once. With several escape routes barred, the cancer will not be able to break free of the drugs stopping its growth.