Even seemingly healthy cancer survivors often complain of extreme fatigue. They have completed treatment and their test results are clear, but they feel empty and unable to walk to the mailbox or stay awake through dinner.
Lethargy can last for years and has become a major unexplained symptom that clinicians have been able to measure only with subjective and imprecise surveys.
However, a pilot study was published biomedical science Clinicians will have better measurement tools, which may ultimately lead to better treatments.
Researchers from Rutgers University, Johns Hopkins University, and the National Institute on Aging used a specialized MRI to directly look at the skeletal muscle cells of 11 cancer survivors and measure how quickly their mitochondria, the organelles that produce cellular fuel, rebuild their energy stores after exercise.
Until now, no one had deeply studied the single cell-specific biology that could drive the cancer patient experience. Although there have been several previous studies on blood mitochondria levels, blood composition is constantly changing. Every time you sneeze, your blood cells change. ”
Leori Sarrigan, lead author of the study, professor and associate dean for research at Rutgers School of Nursing
Along with RWJBarnabas Health, Mr. Saligan is also a member of the Cancer Prevention and Control Program at Rutgers Cancer Institute, the only NCI-designated comprehensive cancer center in the state.
The research team used an MRI test validated by the National Institutes of Health to measure mitochondria called phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Participants lay inside the scanner with the coil applied to their left thigh. After a short period of intense knee extension exercise to deplete energy stores, the scanner tracked recovery. Longer recovery times indicate decreased mitochondrial function.
The 11 participants were between 34 and 70 years old and had been treated for various cancers with surgery, chemotherapy, radiation therapy, immunotherapy, hormone therapy, or a combination thereof.
Participants aged 65 and older had approximately 10% slower muscle energy recovery, weaker grip strength, higher self-reported fatigue, and took fewer steps each day than younger patients. Treatment type also predicted muscle recovery to some extent, but the treatment categories overlapped and most participants received more than one treatment. Participants who received immunotherapy reported increased fatigue, slower muscle recovery, weaker grip strength, and fewer daily steps than those who did not receive immunotherapy.
The most provocative finding was counterintuitive. Among younger participants, those with worse mitochondrial recovery reported feeling less fatigued, but not more. At the same time, worse mitochondrial recovery in that group correlated with improved resilience and coping self-efficacy. The researchers cautioned that this may reflect statistical instability in such a small sample. Nevertheless, the possibility also arises that subjective fatigue and cellular energy capacity partially function through different pathways.
“This just shows that the subjective experience of fatigue is very multidimensional,” Sarrigan says. “It’s not just the physical aspects that define the experience of the condition.”
This study has important limitations, including a small sample size and a mix of cancer types and treatments.
The researchers said the value of this study lies in demonstrating the feasibility of this approach. If 31P-MRS can provide a stable, non-invasive measure of mitochondrial function in cancer survivors, it could ultimately serve as a biomarker linking the biology of post-treatment fatigue with the subjective experience described by cancer patients.
Sarrigan said the next step is to replicate the study in a larger cohort. A further goal is to simultaneously measure brain and skeletal muscle energy recovery.
“It’s really important to see how quickly exercise actually accelerates muscle recovery, but also the utilization of energy within the muscle,” Sarrigan said. “I think this is very important for survivors, not only in the amount of exercise, but also in the timing of the exercise program.”
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Reference magazines:
DOI: 10.3390/Biomedicine14020448
