A Wayne State University researcher believes the condition affects some patients much more than others and is trying to determine the nature of that difference.
Horng-Shiuann Wu, Ph.D., assistant professor of nursing in the College of Nursing, has made an effort to chronicle the parameters of what she calls sudden exhaustion syndrome. Her study, "Definition, Prevalence and Characteristics of Sudden Exhaustion: A Possible Syndrome of Fatigue in Cancer," recently published in the journal Supportive Care in Cancer
, is an effort to differentiate between types of cancer-related fatigue (CRF), a condition that affects upwards of 90 percent of patients who undergo major treatments and 30 to 67 percent of cancer survivors.
"CRF is something that goes far beyond just being tired," Wu said. "It's more draining, more intense, lasts longer than typical fatigue and is often unexpected."
As a graduate student, Wu became interested in a subset of patients who reported fatigue as a "hit-the-wall" moment that came on suddenly, left them barely able to move and often forced them to lie down immediately until the episode passed.
CRF has been well documented, but while many clinicians and researchers have heard anecdotally from patients about suddenly "hitting the wall," such reports have not been addressed directly by studies.
Wu's team studied 114 breast cancer chemotherapy patients aged 31 to 67 from a Midwestern clinic and an urban teaching hospital. Participants were screened for sudden fatigue and completed a questionnaire on the day of their chemotherapy treatment. Descriptive statistics were used to examine the prevalence and clinical characteristics of sudden fatigue episodes, including an intensity rating system from one to 10, the latter level being the highest.
Just under half (46 percent) of participants experienced sudden fatigue. Of those, 81 percent reported more than one episode per day, with 77 percent of episodes taking place during activities between 10 a.m. and 5 p.m. Ninety percent of patients described the intensity as severe.
Most episodes lasted an hour or less, but some lasted up to eight hours. Some patients had to sleep; others did not. Many reported concurrent symptoms including weakness, dizziness, pain, sweating, nausea and shortness of breath.
"We learned that this is something that's really happening and most patients' lives are affected by it," Wu said.
Because the sudden onset of such episodes distinguishes them from what's normally thought of as CRF, she believes "sudden exhaustion syndrome" is a better description.
"Patients can suddenly become so exhausted they cannot move at all," Wu said. One participant experienced an onset while being surveyed, causing her eyelids to droop and rendering her unable to form words.
She said the study shows that patients undergoing treatment endure a lot, and she is interested in looking at which syndrome characteristics particular patients experience, along with degrees of intensity and concurrence.
Wu also would like to know why some patients feel compelled to sleep and others do not, and what symptom changes signal to each person that an episode is ending. She is especially curious about patients who seem to experience little or no CRF.
The condition may even continue for many cancer survivors even after they've finished treatment. Wu believes, however, that in the absence of empirical evidence of that continuation, further research is needed.
For now, Wu said oncology professionals need to recognize the syndrome and educate patients to enhance a sense of control and prevent harm.
"Cancer is not going away anytime soon," she said. "Most people experience their illness through the symptoms, not the illness per se. But we can manage a symptom, even if we can't cure the illness yet."