Some of America's best cancer hospitals are off-limits to many of the people now signing up for coverage under the nation's new health care program. Doctors and administrators say they're concerned. So are some state insurance regulators. An Associated Press survey found examples coast to coast. Seattle Cancer Care Alliance is excluded by five out of eight insurers in Washington's insurance exchange. MD Anderson Cancer Center says it's in less than half of the plans in the Houston area. Memorial Sloan-Kettering is included by two of nine insurers in New York City and has out-of-network agreements with two more.