The source novel series indicates that advanced anti-radiation "Meds" are a reality. Dosages of radiation that would normally kill a human somehow become a chronic condition (one that requires careful administration of these drugs on an ongoing basis) rather than a fatal one.
“I’ve never actually seen the detector activate,” Miller said, his voice rough and faint after his coughing fit. “What does it mean when the thing is red?”
“It means we’ll be bleeding from our rectums in about six hours,” Holden said. “We have to get to the ship. It’ll have the meds we need.”
“What,” Miller said, “the fuck… is going on?”
Back in the protective shell, he took off the vac suit and hooked the air supply to the recyclers to charge up. With only one person to care
for, even low-level life support would have it ready to go within the
hour. The ship batteries were still almost fully charged. His hand
terminal chimed twice, reminding him that it was once again time for
the anti-cancer meds. The ones he’d earned the last time he’d been on
Eros. The ones he’d be on for the rest of his life. Good joke.
Holden had been a naval officer for six years. He’d seen people die,
but only from the vantage of a radar screen. On Eros, he’d seen
thousands of people die, up close and in horrific ways. He’d killed a
couple of them himself. The radiation dose he’d received there meant
he had to take constant medications to stop the cancers that kept
blooming in his tissues. He’d still gotten off lighter than Miller.
Evidently these medications are in short supply and not cheap.
“I got three cousins died because Earth corporations wouldn’t sell the good cancer meds to Belters. Gave us the crap left over from the farms on Ganymede. Only vat meats aren’t like people, yeah? Don’t work the same, but who cares?
Apparently this class of drugs are referred to as "oncocidals". They work by preventing unwanted cellular division.
“What?” Fayez said. “He’s overcooked? The eye thing only likes us rare, and he’s well done?”
“Oh,” Elvi said. “It’s his oncocidals. After the Eros incident, he had to go on a permanent course of them. And that means… oh! That’s so pretty.”
“Oh good. What are you talking about? Why would his anti-cancer meds work on something from a different biosphere?”
“It means there’s a Dawkinsian good move down around cell division somewhere.”