LITTLE ROCKFor patients with cancer-related fatigue, "the first
line of treatment, in my opinion, is to increase their hemoglobin levels so
that they can begin an exercise program," noted William Evans, PhD.
"Cancer patients suffering from primary fatigue should not be advised
to increase the amount of daily rest. Rather, they should be counseled to
carry out aerobic exercise," he explained. Dr. Evans serves as
director, nutrition, metabolism, and exercise, and professor of geriatrics,
physiology, and nutrition at the University of Arkansas for Medical Sciences
in Little Rock.
An exercise physiologist by training, Dr. Evans noted that fatigue is
related to reduced aerobic capacity, which can be measured by VO2max
(cardiac output times the arterial/venous oxygen difference). VO2max varies
enormously, with values ranging from 60 mL/kg/min. and up for professional
athletes, to 50 and below for sedentary individuals. In cancer patients, VO2max levels have been measured below 20 mL/kg/min.
Benefits of rHuEPO
Dr. Evans reviewed one randomized prospective study examining the
protective effects of recombinant erythropoietin (rHuEPO) on metabolic and
exercise capacity in cancer patients losing weight. The study involved 108
cancer patients, most with gastrointestinal cancers, randomized to oral
indomethacin alone or with rHuEPO.
Despite being "somewhat complicated by a huge drop-out rate,"
the results clearly showed that hemoglobin levels and exercise capacity
continued to drop in patients who did not receive rHuEPO, while patients who
received it maintained relatively high hemoglobin levels of about 13 g/dL
and increased their exercise capacity (see Figure 1). "The conclusion
was that anemia is effectively overcome by rHuEPO in unselected cancer
patients. Treatment of anemia preserved physical function, defined as
exercise power and whole body metabolic efficiency," Dr. Evans said.
"There is a remarkably strong relationship between change in VO2max and
change in hemoglobin," he continued, "and at submaximal exercise
capacities, restoring hemoglobin levels results in increased cardiac output
and a change in heart rate and lactate."
Cancer fatigue is probably due not only to anemia, but also to loss of
muscle mass resulting from cachexia, and severe deconditioning, Dr. Evans
said. "Many cancer patients who become anemic and lose muscle mass are
likely to be very inactive. Increasing their hematocrit may allow cancer
patients to participate in a regular conditioning program to resolve this
issue of severe deconditioning."
Reviewing the somewhat sparse literature on the subject, Dr. Evans found
that cancer patients losing weight or suffering from severe fatigue had
greatly reduced VO2max, equivalent only to the oxygen cost of simply walking
at a normal pace of about 2½ miles per hour. "Most of the activities
of daily living are well above the so-called anaerobic threshold of most
cancer patients," Dr. Evans said. "That tells us two things: that
their fatigue is related to their anemia and low VO2max, but also their
severe deconditioning." The anaerobic threshold is the point when
muscles begin producing more lactic acid than they consume and spill lactic
acid into the blood, increasing respiration rate. Above the threshold it is
extremely difficult to work without becoming fatigued.