The guy who launched a startup while fighting brain cancer is suing his insurance company

The day Porch.com cofounder Ronnie Castro's daughter was born was one of the highlights of his life.

But the very next day was one of the worst. That's when he found out he had a rare type of brain cancer with only a 50 percent chance of survival.

And now, he's suing his insurance company for denying him coverage for a type of radiation treatment, proton therapy, which Castro underwent even after the insurance company told him it wouldn't pay for it.

The treatment put him hundreds of thousands of dollars in debt.

Thanks to a campaign on GiveForward, his friends and family rallied around him to raise $115,000 (and counting) to help him pay those bills. (He's hoping to raise $160,000.)

Castro's story is scary and inspiring.

The scary part: He had gone to the doctor for what he thought was a sinus infection and the doctor made him do a routine MRI. Against all odds, it was a rare form of brain cancer.

The inspiring part: brain cancer didn't stop him from launching a cool startup, Porch.com, with his one of his best friends, Matt Ehrlichman. (Ehrlichman sold his first startup, Thrive, to Active.com for $60 million in 2007 at age 28.)

Porch.com lets you see pictures of cool renovation projects in your neighborhood and connects you to the remodeling pros that did those projects. It was founded in 2013 and came out of stealth shortly after Castro's diagnosis that same year.

It has done well since, growing to 400 employees, raising just under $100 million in venture funding, and showcasing the work of 3.2 million professionals over 132 million projects.

At the time of Castro's diagnosis, he had LifeWise Health Plan of Washington insurance. The insurance company said that the proton therapy was experimental/investigational and therefore not covered by his plan.

Castro and his lawyers believe they've got a case against that decision, according to the legal complaint they shared with Business Insider.

Whether they'll win is for the courts to decide. But he's fighting the insurance company hoping he'll help other brain cancer patients get insurance coverage for their treatment, his representative tells us.

When he was first diagnosed with cancer, he wrote a blog post about it and included a picture of his scar with the mantra, "If its beatable, I'll beat it."

Looks like he's taking that same attitude with the insurance company.

We've reached out to LifeWise for comment and will update when we hear back.