Cancer Rehabilitation and the Importance of Balance Training

Effects of chemotherapy on balance and sensation of cancer patients In the past decades, chemotherapy has helped improve the diagnosis and treatment of cancer, and led to an increase in cancer survivors (Duregon et al., 2018). However, the most common side effect from of the use of chemotherapy is chemotherapy-induced peripheral neuropathy (CIPN), which impacts patients’ physiological health and psychological health.

CIPN can lead to a change in their quality of life (QoL) due to influences in their neuromuscular system2,3. Patients with CIPN experience pain, muscle weakness, decrease balance control, gait unsteadiness, reduced or absent reflexes (Schmitt et al., 2017). Additionally, it is common to have altered sensation such as numbness, burning, and tingling, along with dysesthesias and paresthesias that follow a stocking and glove pattern in the lower and upper extremities (Duregon et al., 2018). These symptoms may be resolved to a certain extent, but complete resolution is rare1. Motor deficits such as balance impairment, decreased gait speed and lower limb strength can persist, with increases in fall rates (Duregon et al., 2018). The clinical meaningful physical impairments of CIPN leads to a ‘viscous circle’ which impacts patients’ independence to complete activities of daily living (ADLs).

In contrast, promoting a healthy, active lifestyle could increase physical function and postural control, which can decrease fall risks and increase QoL (Duregon et al., 2018).

Figure 1: ‘Vicious circle’ of clinical meaningful impairments due to CIPN (image created from information (Duregon et al., 2018))

Physiological changes of CIPN leading to postural instability There are various underlying mechanisms that cause CIPN, which can lead to postural instability in cancer survivors (Duregon et al., 2018).

Figure 2: Physiological impact of CIPN leading to postural instability (image created based on (Duregon et al., 2018))

Differences between Chemotherapy-induced peripheral neuropathy (CIPN) vs Radiation-induced peripheral neuropathy (RIPN)

Figure 3: Summary comparison of CIPN vs RIPN (image created based on (Delanian et al., 2012; Streckmann et al., 2014b)

Cancer survivors exhibit less postural steadiness than age-matched controls There are 2 major differences between cancer survivors and age-matched controls: 1) Removal of visual input leads to a significant decrease in postural stability

Cancer survivors are much less steady compared to a control group when they were prevented from using vision to maintain balance, or were asked to stand on unstable surfaces (Schmitt et al., 2017). While there may be various factors that lead to differences between cancer survivors and the control group, the groups were closely matched for age and BMI, which rules out these factors as causes for major differences in balance (Schmitt et al., 2017). In fact, cancer survivors require more proprioceptive and vestibular inputs to maintain postural stability, compared to healthy counterparts similar in age (Schmitt et al., 2017).

2) Effects of cancer treatments may have similar effects to aging

Interestingly, the balance of elderly adult cancer survivors (55 years) was similar to the balance of individuals without cancer who were about 15 years older (Schmitt et al., 2017). As a result, cancer survivors demonstrated postural stability characteristics that were reflected a more elderly population (Schmitt et al., 2017). A possible explanation would be that the effects of cancer treatments, are similar to the effects of aging, where both lead to a decrease in postural control (Schmitt et al., 2017).

Multifaceted benefits of balance training for cancer survivors

Figure 4: Benefits of cancer rehab such as improvements in aspects of balance, functional performance, and guidelines for future treatments (image created from (Duregon et al., 2018)) The most significant improvements to postural control were combined exercise protocols which involved endurance, strength, and sensorimotor training (Duregon et al., 2018). As well, exercise sessions led to an increase in patients’ QoL and independence (Duregon et al., 2018). I) Benefit I: Static balance control

There were significant improvements in static balance control when programs included three major components in each exercise session which are sensorimotor training and postural exercises, such as tasks that required stabilization (Streckmann et al., 2014b), closed kinematic chain exercises, and stability training focused on engaging the core during balance exercises (Schwenk et al., 2016; Mizrahi et al., 2015; Fernandes and Kumar, 2016).

Clinical recommendations for improving static balance control:

Sensorimotor training focuses on postural control using balance boards, foam pads, elastic bands to challenge balance (Page, 2006). It progressively challenges proprioception to regain normal motor patterns (Page, 2006). An example exercise program that was effective at improving static balance was to progress through 4 different posture exercises, and complete for 3 sets (Streckmann et al., 2014b). Hold each position for 20s, have 20s rest between sets, and 1min between exercise to prevent fatigue. In fact, sensorimotor training has the potential to improve neuromuscular mechanisms that affect balance for various patient populations (Song et al., 2011). Interestingly, diabetic patients who have diabetic peripheral neuropathy (DPN), a type of nerve damage similar to CIPN, had an increase in balance control and trunk proprioception after balance exercises.

Static balance can be measured using a single-leg balance test. After 12 weeks of exercise training consisting of aerobic, resistance, core stability, and balance exercise sessions led to improvements which were maintained after 24 weeks, upon completing a follow up assessment (Mizrahi et al., 2015).

Completing these CKC exercises at least 15 times over 3 weeks can increase the participants’ subjective understanding of the severity of CIPN, and static and dynamic balance (Fernandes and Kumar, 2016). Thus, these exericses can improve postural control over a short amount of time, and are tolerated well by participants (Fernandes and Kumar, 2016).

The improvement in balance may be due to increasing the challenge of the exercises (Fernandes and Kumar, 2016). The exercises were first completed with support, then after a few sessions, the patients were tasked with using minimal support, working their way up to performing the exercises without any support. Furthermore, there was an increase in proprioception and strength of muscles around the ankle joint which may have led to an increase in their balance and decreased incidents of falls (Fernandes and Kumar, 2016).

II) Benefit II: Dynamic balance control

Exercise training for cancer survivors can improve dynamic balance, or postural control during movement.

Clinical recommendations for improving static balance control:

i) Using obstacle courses (interactive game-based balance training)

Obstacle courses that involved repetitive weight shifting, and crossing-over obstacles, led to significant (43-74%) improvements of dynamic balance (Schwenk et al. (2016)). After the exercises, the sway of the hip, ankle and center of mass had significantly decreased while standing in feet-closed position with eyes open among older cancer patients with CIPN. Significant increases in postural balance may be due to the nature of obstacle courses so that the participant has many opportunities to continuously weight shift (Streckmann et al., 2014b). The most significant improvements to dynamic balance were observed in the monopedal (single leg) stance (Streckmann et al., 2014b). Individuals without access to game-based balance exercises can include obstacle courses in balance training programs, so the participant can utilize dynamic control repetitively, for prolonged periods of time.

ii) Gait training

Furthermore, dynamic control for people with CIPN can be improved by using gait training (Streckmann et al., 2014b). In fact, people with CIPN can exhibit gait patterns similar to diabetic patients with DPN who have prolonged time in stance phase, slower speeds, and reduced step length as a strategy to maintain stability in walking (Mustapa et al., 2016). Walking tasks (tandem walk, or different types of gait patterns), functional exercises (sit to stands from a chair, climbing stairs, walking up and down an incline, or small hops), and progressively increasing the complexity of tasks (dual-tasking by adding in head rotations or verbal tasks like counting by 10’s) have been proven to be effective for patients with DPN (Allet et al., 2010).

iii) Mechanical perturbations

An effective way to challenge the participant’s dynamic balance when they have gained back more postural control, is to add in mechanical perturbations (Streckmann et al., 2014b). Mechanical perturbations is a method of adding in tasks that suddenly change the participant’s center of mass, so they learn to adjust their balance according to unexpected changes. For example, by tieing a theraband around the participant’s knees, and asking them to stand on one leg, while shifting the theraband at random intervals, can challenge the participant to regain postural control after an external force.

III) Benefit III: Quality of life and physical function

Although a balance rehab program that had a combination of aerobic, strength, and sensorimotor training did not significantly improve the fear of falling, the lack of change may be due to the short-term, 4-week intervention period of the program. In fact, balance programs that lasted from 10-36 weeks improved quality of life, and the benefits remained at the follow up period (Mizrahi et al., 2015). Thus, longer balance rehab programs may be more effective at QoL and long-term changes for people with CIPN.

Interestingly, balance rehab programs helped patients with the adverse effects of chemoptherapy by introducing breathing techniques, and stretches (Fernandes and Kumar, 2016). Thus, alternatives to exercise-based balance rehab programs, such as yoga, which focus on breathing techniques, and stretches may be beneficial to improve aspects of QoL for patients with CIPN (Fernandes and Kumar, 2016).

In addition, exercise-based balance rehab programs improve upper and lower body strength, and lower body functional abilities over a long-period of time, which can lead to adapting a healthy, active lifestyle change (Mizrahi et al., 2015). Exercise helps to prevent the effects of physical inactivity during chemotherapy, such as muscle atrophy, osteopenia, decreased cardiorespiratory fitness, decreased insulin sensitivity, decreased immune function, and increased risk of chronic illness (JAMA, 1996).

Balance training and impact on sensation

Balance and exercise training can help people with sensory neuropathy, which is common to CIPN (Hilkens and Van Den Bent, 1997). After 15 sessions of CKC exercise, patients state they have a decrease in tingling sensation and pain, and return to having normal sensation for a pin prick and vibration in the lower limbs (Hilkens and Van Den Bent, 1997).

Outcome measures for cancer patients

Clinicians can use the BESTest and its short versions (Mini-BESTest, and Brief-BESTest) (https://www.physio-pedia.com/Balance_Evaluation_Systems_Test_(BESTest), http://www.bestest.us/test_copies) to assess and identify balance problems amongst older cancer survivors (over age of 55) who lived in the community (Huang et al., 2016). The BESTest and its short versions has high interrater and test-retest reliability, and exceptional concurrent validity with the ABC Scale for this patient population. The minimal detectable change MDC is 2.39-6.86 points, which can be used detect significant and relevant changes to balance (Huang et al., 2016).