Impact of Physical Inactivity on the Multifactorial Process of Developing Cancer-Related Cognitive Impairments

Many cancer survivors report cognitive impairment before, during and after medical treatment. It is well known that many factors other than chemotherapy take part in the development of these cancerrelated cognitive impairments (CRCI), such as cancer-related fatigue, psychological as well as molecular factors. The purpose of this review is to describe the impact of physical inactivity in the genesis of these cognitive changes in cancer patients. References for this narrative review comes primarily from PubMed, Cochrane Library and Livivo databases. It contains literature search from October 2003 to April 2016. Our search was focused on available data for the influence of physical inactivity on cognitive performance of cancer patients. Cancer patients have decreased levels of physical activity during treatment. It is suggested that lack of physical activity in general is associated with cognitive decline. At present, most available data comes from trials with heart failure patients as well as results from bed rest studies in space medicine. The development of CRCI is a multifactorial process with physical inactivity appearing to play an important role. However, the available data remains limited and future trials are needed to examine the specific role of physical inactivity on CRCI. [14-16]. The role of physical inactivity in the multifactorial process of CRCI development has not been extensively described and is the focus of our review (Figure 1). Materials and Methods This narrative review has been divided into four sections: 1) multifactorial aspects generating CRCI, 2) the role of physical inactivity, 3) discussion, and 4) conclusion. Information from this narrative review was obtained by searching the PubMed, Livivo and Cochrane Library databases from October 2003 to June 2016. A first search focuses on the influence of physical inactivity on development of cognitive impairments in cancer patients. Therefore, a combination of following terms was used: on the one hand “cancer-related cognitive decline”, “cancer-related cognitive dysfunctions”, “cancer-related cognitive impairments”, “chemobrain”, “chemofog”, “post-chemotherapy cognitive impairment”, “cancer brain”, “cancer associated cognitive impairment”, “cancer-therapy-associated cognitive impairment” and on the other hand “bed rest”, “immobilization”, “lack of exercise”, “physical inactivity”. There were no publications referring to this aspect exclusively. As such, a second search was conducted focusing on influence of physical inactivity on cognitive performance in general. Therefore, a combination of the following terms was used: “physical inactivity”, “bed rest”, “immobilization”, “lack of exercise” and on the Citation: Pesendorfer LM, Zimmer P, Galvão DA, Bloch W, Baumann FT (2016) Impact of Physical Inactivity on the Multifactorial Process of Developing Cancer-Related Cognitive Impairments. J Cancer Sci Ther 8: 222-227. doi: 10.4172/1948-5956.1000417 J Cancer Sci Ther ISSN: 1948-5956 JCST, an open access journal Volume 8(8) 222-227 (2016) 223 changes might be associated with impaired memory performance and difficulties in learning [4,5,22-27]. In rodent research, it is also reported that cytostatic agents (e.g. carmustine, cytarabine, cisplatin, 5-FU, MTX) affect the oligodendrocytes which may lead to damage of the white matter [21,24,26-28] hence potentially reducing speed of information processing [27]. Furthermore, cytostatic therapy induces reduction of the gray matter in certain brain areas, such as the cerebellum and the prefrontal cortex. Loss of gray matter density seems to be associated with impairment in executive functions, verbal memory und working memory [9,19,29]. Several anti-tumor therapies also appear to lead to alterations in cerebral blood flow. For example, some medical treatments induce cerebral hyperperfusion accompanied by impairment in neuropsychological test performance. In contrary, a decrease of gray matter density in those brain areas is associated with cerebral hypoperfusion [20].