This analysis of physical activity status among a large heterogeneous cohort of adult survivors of childhood cancer indicates that they are less active than either the siblings in the study or the general population of similar age and sex. While statistically significant, the percentage differences in individuals who do not meet CDC physical activity guidelines are probably not clinically meaningful. What is more important is that the prevalence of no activity over than past month is 60% higher among childhood cancer survivors when compared to siblings. Our results characterize the features of survivors who are in particular need of interventions that promote physical activity. These include survivors who are female, black, older, underweight or obese, as well as survivors of CNS or bone tumors, especially those who had cranial radiation or an amputation.
Our study population reports less physical activity than other groups of childhood cancer survivors, including adolescents and young adults,44-46
but more physical activity than a smaller group of childhood cancer survivors comprised of nearly half CNS tumor survivors.47
Keats et al.45
reported average participation in combined moderate and vigorous physical activities 5+ times per week, 36-42 minutes per time, among 51 adolescent survivors. CNS tumor survivors comprised 13%, and osteosarcoma survivors 8.5% of their cohort. Tercyak et al.46
reported adequate physical activity among 80% of 75 childhood cancer survivors 11-21 years of age. Just over half of these individuals were females; 52% were leukemia survivors. Finnegan et al.44
indicated that 81% of childhood cancer survivors, recruited via the internet, reported being physically active. These survivors were younger (18-37 years) than our cohort, and were mostly well educated, Caucasian, females. The proportions of CNS tumor (13% vs. 10%) and bone tumor (8% vs. 11%) survivors in our cohort were similar to the proportions in their study. A small group of adult survivors of childhood cancer in Queensland, Australia were less active, with only 36% reporting sufficient physical activity.47
This group of individuals included a greater percentage of CNS tumor survivors (43%) and more females (61%) than our study.
Our study is the first that we know of to report differences among percentages of individuals who met the nationally recommended guidelines for physical activity in a large heterogeneous cohort of cancer survivors, siblings and a population-based comparison group. Our study includes the all diagnoses in the CCSS cohort, and differs from a previous CCSS report where analyses were limited to survivors of acute lymphoblastic leukemia (ALL).48
Our data analyses include data summarized by Florin et al.48
and confirm and extend the findings that female gender and cranial radiation are associated with inadequate physical activity. Our analyses also include siblings of cancer survivors, who report physical activity levels similar to the population based group from the BRFSS, dispelling the notion that siblings of cancer survivors who participate in research introduce either healthy or sick participant bias into the study design.49
The demographic and treatment related risk factors identified in our analyses are supported by other investigators who have demonstrated lower than expected levels of physical activity among adults who were treated for CNS malignancies and bone tumors during childhood, particularly among female survivors. Odame et al.50
reported reduced physical activity levels in a group of 25 survivors of childhood CNS tumor who were 5-29 years of age at evaluation, with scores on two different activity indices lower among those who received cranial radiation when compared to those who did not receive cranial radiation. Gerber et al.51
evaluated 30 survivors of pediatric sarcoma and found that 67% had activity levels below the 50th
percentile for their age and gender. Problems were most pronounced among those with lower-extremity or trunk lesions, and among females.
Several study limitations should be considered in the interpretation of these results. First, physical activity was evaluated with self report data that could not be validated. However, over-or under-reporting of physical activity have been evaluated in one study that compared self-reported physical activity on the BRFSS survey to objective monitoring with motion sensors and a heart rate monitor.52
These authors found 80% agreement between the two methods of classifying individuals who did or did not meet the national recommendations for physical activity. Additionally, two of the personal/demographic variables in our model that influenced physical inactivity, obesity and employment status, were measured simultaneously with the physical activity outcomes. We therefore can not be sure of the direction of these associations. Participants may have an inactive lifestyle because they are obese or obese because they have an inactive lifestyle. Participants may have an inactive lifestyle because they are busy looking for a job, or unemployed and sedentary because disability prevents participation in either activity. Finally, these analyses include cancer survivors treated between 1970 and 1986. Because therapy has evolved in response to the documentation of medical late effects, fewer children are receiving cranial radiation or amputation as part of treatment. Not all of our results may be generalizable to children treated with more contemporary therapy. However, this information is applicable to the large cohort of young adult survivors of childhood cancer who were treated on earlier protocols, and to the groups of individuals who still receive chemotherapy that promote obesity, cranial radiation, and extensive lower extremity surgical procedures.
In summary, childhood cancer survivors are less likely than members of a sibling comparison group, or an age- and gender-matched group of BRFSS survey participants to meet the nationally recommended guidelines for physical activity. Female survivors, survivors with obesity or chronic disease, survivors who received cranial radiation and those whose treatment required extensive surgical intervention may benefit from targeted interventions that address unique barriers to participation in regular physical activity.