After being stricken with seizures on the 4th of July, Maureen Reagan, eldest daughter of former President Reagan, is undergoing radiation treatments for melanoma that has spread to her brain, her husband said Friday. Reagan, 60, is receiving care at Mercy San Juan Hospital in Carmichael, near the family's Northern California home, said Dennis C. Revell, 48, her husband of 20 years. "She believes that there are many factors that help a person survive, from the power of one's faith and prayers to support of family and friends to the quality of one's medical care to maintaining a positive attitude," Revell said. Last November, a golf ball-sized malignant tumor was discovered in her right pubic bone and she underwent 3 1/2 months of aggressive chemotherapy treatments at the John Wayne Cancer Institute at Saint John's Health Center in Santa Monica, near her father and stepmother Nancy's home. (Maureen's mother is Reagan's first wife, actress Jane Wyman, 87.) She appeared to be conquering her cancer when she was released from the hospital March 23. She returned home and was put on a 12-month, self-administered biotherapy program, Revell said. Wyman has visited her daughter, and Nancy Reagan has telephoned her daily. "I saw her a little over a week ago and told her that her dad and I love her and we're praying for her every day," Nancy Reagan said in a statement.