Jessica Simpson's father, Joe Simpson, has started radiation treatments for his prostate cancer, Us Weekly is reporting.

"Joe just started radiation. He feels fine, he's getting through it and still working. It's all scheduled once a week. He's super optimistic," a source tells the magazine. "Doctors are hopeful that this will take care of it and be the last step, and he will hopefully then be in remission and cancer-free. Joe just says he feels like it's like going to get a checkup."

Despite his health issue, Joe, 58, has been getting very involved in his photography work, which often serves as a distraction.

"He's just working and hanging with his kids. He's not slowing down at all. He's actually been doing some bigger campaigns and shoots. He wants to keep his mind off of it," the source said. "His work helps it."

Last November, it was revealed that Joe had been diagnosed with cancer and had undergone surgery.

Both Jessica and her younger sister Ashlee were "super supportive" of him. In fact, Us' source said he has grown closer to his children ever since the diagnosis, particularly Jessica, who he had apparently drifted with in recent years.

On Christmas, Joe shared an image of he and his eldest daughter.

"Beginning Christmas with my first Christmas present!!!," he wrote.

"This had made their relationship stronger. She's been awesome," Us' source said. "Jessica was the one he wasn't as close with, and this made them so close. They're all closer because of what he's going through."

After reports surfaced of his diagnosis, Joe took to Instagram to call cancer "the dream killer." The one-time "dadager" (the opposite of a momager) later took down the social media post.