No one ever checked whether Leslie Bather's breast cancer was spreading to her brain, until the day tumors caused three frightening seizures. MRI scans can help spot when cancer in another part of the body sends seedlings into the brain, but few patients get routine checks.

Neurology specialists say it's time to change that: More patients are surviving initial tumors long enough for their brains to be at risk, as treatments get better at battling cancer below the neck yet fail to protect the brain. And improved technology is making it easier and safer to treat those new brain tumors, if they're caught early.

"If I were diagnosed with cancer tomorrow, the first thing I'd want is a brain scan," says Dr. Leonard Cerullo, director of the Chicago Institute of Neurosurgery and Neuroresearch.

This type of brain cancer "is becoming a bigger and bigger clinical problem," adds Dr. Frank Lieberman, neuro-oncology chief at the University of Pittsburgh Cancer Cancer.

Already, about 150,000 Americans a year are diagnosed with what is called a "metastatic brain tumor" — cancer that spread into the brain from some other part of the body.

Any cancer can spread to the brain. But lung cancer is the leader; it will happen in up to 40 percent of lung cancer patients, often very early in their disease.

Up to a third of breast cancer patients will experience a brain metastasis. Also common spreaders are melanoma and kidney and colon cancer.

Not too many years ago, doctors mostly discovered metastatic brain cancer when its victims already were close to dying from tumors riddling other parts of their bodies.

Now, breast specialists in particular are reporting an increasing number of women who beat back cancer elsewhere in the body, only to have it flare in the brain. It seems to be a special concern among users of Herceptin, a powerful drug that targets an aggressive type of breast cancer — everywhere except in the brain, because it's too large a molecule to penetrate the blood-brain barrier, explains Lieberman.

But it's a more widespread concern. While the American Cancer Society doesn't yet have a count of the reported increase, it notes that cancer patients overall are living longer, providing more time for microscopic tumor cells incubating in the brain to take root.

Scientists are beginning to fight back:

--Studies are under way to see if an experimental drug called lapatinib, made by GlaxoSmithKline, can treat breast cancer that spreads to the brain. Lapatinib targets the same aggressive breast cancer as Herceptin does but is thought to easily penetrate the brain.

--Also under study is whether some commonly used cancer drugs could ever cross into the brain, especially if used in conjunction with brain radiation.

--And neurology specialists are urging general oncologists to start checking patients, especially those with lung or breast cancer, for spread to the brain well before symptoms appear.

There are no formal guidelines, but at Pittsburgh, MRI scans — not CT scans that Lieberman calls less sensitive in the brain — are being incorporated shortly after original diagnosis. After that initial scan, Chicago's Cerullo advises including the brain in any routine check for cancer spread. He says insurance generally pays.

High doses of whole-brain radiation once were the only treatment for metastatic brain cancer, and could cause such troubling side effects as memory loss, Cerullo says.

Now, treatment is more sophisticated, especially for tumors caught early. Topping the list: radiosurgery, using focused beams of radiation to zap just the cancerous cells and not surrounding healthy brain tissue.

Whole-brain radiation today comes in safer doses with fewer side effects, but when to use it is controversial. Some studies suggest a preventive course could protect certain lung cancer patients, for example.

Lieberman and Cerullo advise patients to ask about a brain scan.

It's advice that Bather, the Chicago patient, echoes. She calls her 2004 seizures "definitely divine intervention" because only then did she get a brain scan — even though tests that same week had found breast cancer spreading in her lungs and liver.

"You want to think you're OK," says Bather, 52, whose brain seems clear after treatment of more than 40 tumor sites, but she still is battling cancer elsewhere. Instead, "what you don't know can hurt you."