The rigors and challenges of spaceflight are remarkably similar to the physical stress cancer patients experiment during chemotherapy and other treatments, according to researchers.
For that reason, the researchers suggest that the countermeasures program used by astronauts before, during and after spaceflight to maintain their health could be developed and applied for cancer patients to help them recover after treatment.
The details were published in a commentary written by researchers from Memorial Sloan Kettering Cancer Center and NASA on Thursday in the journal Cell . The work was supported by the National Cancer Institute.
"It was surprising when we looked at similarities between astronauts during spaceflight and cancer patients during treatment. Both have a decrease in muscle mass, and they have bone demineralization and changes in heart function," said Jessica Scott, senior author and an exercise physiology researcher at the Memorial Sloan Kettering Cancer Center's Exercise Oncology Service. "Astronauts may get something called space fog, where they have trouble focusing or get a little forgetful. That's very similar to what some cancer patients experience, which is called chemo brain."
But astronauts and cancer patients are advised in a completely different way from each other, despite the similar issues they face. The authors of the commentary looked at the countermeasures program created by NASA to see how it might be applied to cancer patients.
For 58 years, NASA has been sending humans into space, with flights ranging from 15 minutes in duration in 1961 to nearly a year on the International Space Station for current astronauts.
The quest for countermeasures to help humans remain stable and healthy in space began early. They didn't know what effect zero gravity might have on the body or specific organs. And they were mainly concerned with cardiac injury, so multiple assessments were used to monitor that activity before, during and after flight, according to the commentary.
NASA's concerns were valid. Apollo astronaut James Irwin had an undetected coronary heart disease and 21 months after returning to Earth, he suffered an acute myocardial infarction, the authors wrote.
Initially, the Project Mercury astronauts, announced in 1959, had to run each day for a month before their spaceflight. Gemini astronauts exercised before their missions and during spaceflight as well, using bungee cords. By the time space station missions began in 2001, NASA had astronauts performing a combination of aerobic exercise and strength training during their 91- to 215-day missions.
Now, in the months prior to their launch, astronauts work with specialists to create a strength, condition and rehab program to create a baseline before flight. They continue the program using equipment on the station. When they return, the astronauts are monitored as they exercise to be sure that their fitness returns to the baseline level established before spaceflight.
After more than 50 years of human spaceflight, researchers know some of the risks posed to the human body by being in zero gravity. Astronauts have to deal with a stressful environment, noise, isolation, disrupted circadian rhythm, radiation exposure and a headward fluid shift that happens when floating as opposed standing on solid ground.
Over time, astronauts staying for six months or more on the station can experience the weakening and loss of bone and muscle atrophy. Astronauts also experience blood volume loss, weakened immune systems and cardiovascular deconditioning since floating takes little effort and the heart doesn't have to work as hard to pump blood, according to NASA's Human Research Program.
The countermeasures were developed to mitigate these risks. But as the authors of the commentary point out, "Cancer is the only major chronic disease condition in which a comparable countermeasures program is not an aspect of standard management."
In contrast with astronauts who are asked to exercise and monitor the levels of their cardiorespiratory fitness, cancer patients are advised differently.
"That's completely backwards to how it is on Earth, where cancer patients may still be advised to rest in preparation for and during treatment and may have to ask permission to exercise from their physicians," Scott said.
While NASA was studying how to keep astronauts healthy and safe in the 1960s, doctors were striving to discover new cancer treatments, the authors wrote. Only 50% of cancer patients survived five years beyond diagnosis. Doctors were trying to manage tumors, reducing their size and the way they spread.
Now, 90% of patients survive early-stage cancer, the researchers said, but there are no current investigations into countermeasures to help the stresses and toxicity their bodies face during treatment.
Currently, managing toxicity falls to pharmaceuticals that target the function of individual organs. That doesn't help patients recover to their normal levels before being diagnosed.
"That's why it's very timely that we start thinking about how to utilize NASA's tactics to manage some of these long-term side effects of cancer treatments," Scott said. "Many patients aren't dying from their cancer, but they're now at risk of dying from these side effects. Using NASA's exercise plan could help with this."
The researchers suggest that even walking on a treadmill could help cancer patients, as well as tests to monitor their fitness over time to develop a baseline level and reduce the risk of heart problems that may occur as side effects from treatment. Scott's team at Sloan Kettering is currently investigating how exercise may offset these treatment side effects.
They have provided the patients with treadmills in their homes, as well as video call capability, to help them exercise before, during and after treatment.
In the commentary, the researchers suggest "proof of concept" randomized trials to test if a countermeasures program would work in an individualized way that begins when patients are diagnosed and follow the patients throughout the process with the goal of helping them maintain as much of a baseline as possible. Wearable devices like smartwatches make it possible for patients to be accountable and be in the privacy of their own home.
"A tremendous opportunity exists to leverage 60 years of space medicine to establish a program of research that optimizes preparation for, tolerability of, and recovery from a cancer diagnosis and treatment," the authors wrote.
The researchers said that in order for the countermeasures program to be viable, it will need to be cost-effective and provide the desired outcomes and benefits. But if it works, it could "change the landscape of cancer care and management."
"We really need to do a lot more research and a lot more work," Scott said. "But it's very promising that this NASA exercise framework could be applied to help the approximately 1 million individuals that will be diagnosed with cancer in the United States this year, as well as the over 15 million cancer survivors in the United States today."