The state Medical Examining Board disciplined four doctors on Tuesday, including fining a Stonington doctor $8,000 for failing to provide adequate follow-up care for a patient who later died of cancer. Dr. David Burchenal of Stonington was also reprimanded and placed on three years of probation under a consent order approved by the board. During the probation, Burchenal must hire a physician to randomly review his patient records and must take a course in assessing urinary tract disorders. In November, the board had rejected a $3,000 fine against Burchenal, with some members saying they wanted a stiffer penalty. Burchenal failed to follow up on test results that showed his patient, George A. Ruffo, had abnormally high red blood cell counts in 2011 and 2012, state records show.