CHICAGO, June 5 (Reuters) - Doctors are closer to predicting which cancer patients can skip chemotherapy and avoid the brutal side effects of that staple of cancer care, doctors at a major medical meeting said on Tuesday.

The move toward helping patients avoid chemotherapy -- and perhaps the nausea, hair loss and weakened immune system that are its hallmarks -- is a positive side effect of the individualization of cancer treatment, doctors at the American Society of Clinical Oncology's annual meeting said.

"Chemotherapy is clearly effective for patients -- on average. But can it be spared?" Dr. Aron Goldhirsch, of the Oncology Institute of Southern Switzerland, said at a panel at the meeting, which wrapped up here.

Women patients with high levels of estrogen receptors -- cancer cells containing special proteins that bind to the hormone estrogen -- are among the patient subsets that may not benefit from chemotherapy for breast cancer, experts said.

More research is needed to determine the best regimes and to define the particular subgroups, said Dr. Kathy Albain, director of the breast clinical research program at Loyola University Medical Center in Illinois.

But it is coming, probably in a few years, she said.

"We have entered the tailored therapy era," Albain said.

Breast cancer is in the forefront in this area, but experts said others are following, including lung cancer which is the leading cause of cancer deaths in the world.

"Now, predictive factors for lung cancer are coming down the pike, rather than just blindly assigning patients to treatments A, B or C," said Dr. Gregory Otterson, who specializes in lung cancer at Ohio State University Medical Center.

So-called targeted cancer treatments -- drugs that attack or bind to a specific molecule or part of a molecule such as one that triggers tumor growth or controls blood flow -- have been around for several years.

What emerged as a theme at this year's meeting is these drugs' effectiveness in more types of the disease, experts said.

"Ten years ago it was all about chemo," said Dr. Kim Lyerly, director of the Duke University Comprehensive Cancer Center. "This time you walk down the convention center and it's all about new targets. And we can get more mileage out these drugs if we can predict who will respond."