Updated at 6:23 p.m. on Thursday, May 3, 2018 with more information.
NASHVILLE - Gov. Bill Haslam on Thursday vetoed legislation that sought to allow employees on the state's health plan use an alternative radiation treatment for cancer.
The Republican said the proton therapy bill "circumvents the established process for determining state employee insurance program coverage based on medical evidence and effectiveness."
Moreover, the governor said "the state plan currently covers many forms of radiation treatment, and the provider advocating this bill rejected a medically appropriate plan for expanded coverage to instead pursue a political mandate."
The bill, sponsored by Sen. Mark Green, R-Clarksville, and Rep. Bob Ramsey, R-Maryville, sought to require coverage of hypofractionated proton therapy for cancer treatment for members of the state group insurance plan.
Green, who is running for Congress, later called for a special session to override the governor's veto.
In his tweet, the physician said his "Cancer Patient Choice Act" would sought to "give cancer patients a proven alternative to radiation at the same price.
"Will you join me in the fight by signing my petition to call for a special session and sharing this post?"
In a joint statement, Lt. Gov. Randy McNally, the Republican Senate speaker, and House Speaker Beth Harwell, R-Nashville, said it's too early for lawmakers, who adjourned for the year only a week ago Wednesday, to call themselves back into session.
"While it is the prerogative of the legislature to call for a special session at any time, we believe it would be premature at this point," the speakers said. "The 110th General Assembly's final bills are still being enrolled, signed and sent to the governor.
"The most prudent course," the speakers said, "is to wait for gubernatorial action on all legislation passed this session. Only then can we reasonably assess the need for a special session."
Haslam's veto of the proton therapy bill was his first veto for the 2018 legislative session that ended April 25. It brings his total vetoes since becoming governor in 2011 to five. Haslam leaves office in January.
The governor said in his veto statement that the state is "committed to high-quality care that is medically appropriate and fiscally responsible for patients and taxpayers, but this mandate could put patients at risk and expose them to excessive charges from out-of-network providers."
Green, a physician, has argued there is "an increased body of literature and medical research that shows that proton therapy is as effective in many types of cancer with a significant decrease in side effects."