WASHINGTON — One of the nation’s leading patient advocacy organizations Thursday urged congressional Republicans not to repeal the Affordable Care Act without first offering a replacement, joining the growing list of voices urging the GOP to slow its Obamacare repeal push. “As members of Congress consider the future of the Affordable Care Act, it is critically important that cancer patients, survivors and those at risk of the disease don’t face any gap in coverage of prevention and treatment,” American Cancer Society Cancer Action Network President Chris Hansen said.