It was the trip of a fly fisher’s lifetime.

But Mark Hopkins’ wrists hurt. There was no way he’d be able to cast a line into the Rio Grande River near the southern end of South America, where the sea-run brown trout migrate up the river to spawn.

He was determined, though, to make his dream come true, arthritic wrists or not.

After relying on four ibuprofen twice a day to manage the pain enough that the former pastor could work on a computer keyboard, he turned to the professionals for pain mitigation. Physical therapy may have helped some, he says, as did the steroid injections he got three weeks before the trip.

And then there was the low-dose radiation therapy he received a few months before his January expedition, which provided maybe the most dramatic relief of all.

Seven months post-trip, his pain remains gone.

“The steroid benefits fall off after about two and a half months, so I have no benefit of that any longer, and I haven’t done physical therapy since December,” he said.

Which means it’s the radiation therapy that was likely the miracle balm that saved his beloved fishing hobby and ability to type for work, though he’s cautious about making a definitive statement.

“There’s a correlation,” said Hopkins, 73, “but you can’t say cause and result.”

However, his results impressed him enough that he received radiation treatment on his right hip earlier this year. The results were nil this time around, but he’s trying a second round.

“It’s painless,” he said. “And if there’s any hope of recovering a style of living that you used to enjoy then why not?”

Hopkins is one of the 70% of patients with osteoarthritis who see a reduction in pain due to low-dose radiation, says Dr. Jeffrey Olsen, the medical director of radiation oncology at UCHealth Memorial Hospital North, where the treatment has been offered for almost a year.

When most people hear the word radiation, they typically think about cancer treatment, which uses high-dose radiation. But low-dose radiation, used for arthritis and other inflammatory conditions, has been around for decades, primarily in Europe. The data had grown so robust that Olsen determined it was safe and offered a clear benefit to patients.

The treatment is best for peripheral joints, like knees, hips and hands, but not degenerative changes of the spine. It’s also not intended for advanced arthritis when a person is experiencing a bone-on-bone scenario, nor is it used as an alternative for a knee replacement.

“It turns out a high dose of radiation has a cell-kill effect, which is how it has that effect on cancer cells,” Olsen said, “whereas a low dose, typically about a 20th to a 40th of a total dose, does not have the same cell-kill effect but does have a strong anti-inflammatory effect.”

In a study last fall, people with knee osteoarthritis were randomized to one of three treatments: no treatment; sham radiation, in which people went into the radiation room and the machine made noise but didn’t deliver treatment; and low-dose radiation.

People who received the sham treatment did find a little more relief than those who received none, and the people who received the actual radiation saw a 70% rate of pain relief, which was in line with European data.

“We started to ask this question in our practice: When we synthesize all the data, is it enough for me? Would I want my osteoarthritis treated if I were to have significant OA?” Olsen said. “And a lot of us look at the data and say yes, I would because the treatment is such low risk and the data is quite in alignment.”

Patients receive treatment twice a week for three weeks. Appointments are about 15 minutes, and they leave feeling the same way they did when they arrived. It’s a one-and-done treatment, with a check-in about four months later to see how they feel. Sometimes, a second round will be administered, but none past that due to a lack of supporting data.

Long- and short-term risks appear to be minimal. Cancer caused by the treatment has never been reported, but that doesn’t mean it’s zero, Olsen says. They always counsel their patients that the risk isn’t zero, but the best estimate is one in several thousand, so it’s still very small.

Side effects are also minimal — mostly mild redness, like a sunburn, which one in 1,000 people reports. If someone is treating OA in their hands, there’s a one in 500 risk of nail irritation.

Like in Hopkins’ case, radiation is not the first line of treatment. Typically, patients will try lifestyle modifications, weight loss and sometimes topical pain relievers. Steroid injections and anti-inflammatories like ibuprofen can help, but there’s a point of diminishing returns when they might do more harm than good. That’s where radiation can come in.

“It really does impact their quality of life in a way that can be pretty profound,” Olsen said. “You see people get back to everyday activities or a hobby they haven’t been able to do. When other treatments haven’t been effective, we’re able to offer something that isn’t effective for everyone but does give a possible pathway.”