DOI: 10.25904/1912/3477
Adjuvant chemotherapy treatment for breast cancer with the widely used anthracycline/taxane combination has potential myotoxic effects on skeletal muscle. More generally morbidity linked to breast cancer treatment may well be associated with physical deconditioning. Together these factors could lead to reduced muscle strength, increased fatigue and consequent decreases in quality of life. Resistance exercise offers the potential to promote improvements in muscle mass and strength, with related benefits in functional capacity and life quality in this population.
The primary aims of this thesis were to investigate the effects of anthracycline/taxa ne adjuvant chemotherapy treatment and resistance exercise on body composition, knee muscle strength, quality of life (QoL) and perceived fatigue in women diagnosed with breast cancer. The study was designed:
Firstly, 19 breast cancer patients (age of 49.8 ± 7.9 years) were assessed pre- and post- chemotherapy. Following chemotherapy, body mass increased (76.6 vs 78.7 kg; p < 0.05), along with body mass index (BMI) (28.4 vs 29.1 kg/m²; p < 0.05), and muscle cross-sectional area (CSA) (67.5 vs 71.3 cm²; p < 0.05). Muscle strength decreased in all four moments tested: isometric extension (2.02 vs 1.83 Nm; p < 0.05), isometr ic flexion (0.79 vs 0.65 Nm; p < 0.05), concentric extension (1.16 vs 0.89 Nm; p < 0.05), and concentric flexion (0.59 vs 0.43 Nm; p < 0.05). Chemotherapy was not associated with any change in whole body lean mass (43.6 vs 43.6 kg; p > 0.05) whole body fat mass (35.4 vs 36.2 kg; p > 0.05), fat CSA (97.6 vs 99.1 m²; p > 0.05) or muscle density (73.9 vs 73.7 g/dL; p > 0.05). After chemotherapy there were no changes in any of the 8 quality of life domains except for a decrease in physical functioning (70.0 vs 61.3; p < 0.05); there were no changes in any of the 5 domains of perceived fatigue except for increased motivation (12.8 vs 11.8; p > 0.05).
Following chemotherapy treatment, the breast cancer group (n = 19; age = 49.8 ± 7.9 years), had greater fat CSA (99.1 vs 78.8cm²; p < 0.05) compared to the healthy control group (n = 27; age = 46.9 ± 10.0 years), but there were no differences between the two groups for either body mass (78.7 vs 71.8kg; p > 0.05) or body mass index (BMI) (29.1 vs 26.5; p > 0.05). Furthermore, there were no differences between the two groups for whole body lean mass (43.6 vs 42.2 kg; p > 0.05) whole body fat mass (36.2 vs 29.6 kg; p > 0.05), muscle CSA (71.3 vs 77.0 m²; p > 0.05) or muscle density (73.7 vs 74.5 g/dL; p > 0.05). Muscle strength was greater in the healthy control group compared to the breast cancer group for all four moments tested: isometric extension (2.1 vs 1.8 Nm; p < 0.05), isometric flexion (0.8 vs 0.7 Nm; p < 0.05), concentric extension (1.4 vs 0.9 Nm; p < 0.05), and concentric flexion (0.7 vs 0.4 Nm; p < 0.05).The healthy women reported better quality of life compared to breast cancer patients who had completed chemotherapy treatment for all 8 domains except for mental health (MH) (75.8 vs 76.3; p > 0.05). There were no differences between the breast cancer group following chemotherapy treatment and the healthy control group for any of the 5 domains of perceived fatigue. The decrease in muscle strength in the breast cancer patients, following chemotherapy treatment, suggests potential impacts on functional capacity and well-being.
For the intervention arm of the study, 14 breast cancer patients (age of 51.9 ± 3.6 years) who had been treated with anthracycline/taxane adjuvant chemotherapy were randomly assigned to either an individualised home-based 12-week resistance exercise program or usual care. The previously mentioned outcome measures were compared between breast cancer groups (Exercise; n = 7, Non-exercise; n = 7) after 12 weeks, and between the breast cancer exercise group and the age-matched healthy women (n = 24; age of 47.1 ± 2.2 years) who had also undertaken the 12-week exercise program. Following the 12-week intervention, the breast cancer non-exercise group showed a higher fat CSA (75.0 vs 129.7 cm²; p < 0.05) compared to the breast cancer exercise group but there were no differences between the breast cancer exercise and non-exercise groups for either body mass (72.8 vs 80.6 kg; p > 0.05) or body mass index (BMI) (24.9 vs 29.9; p > 0.05). Furthermore, there were no differences between the two groups for whole body lean mass (44.8 vs 45.7 kg; p > 0.05) whole body fat mass (32.1 vs 41.7 kg; p > 0.05), muscle CSA (69.7 vs 74.8 m²; p > 0.05) or muscle density (74.0 vs 74.1 g/dL; p > 0.05). Muscle strength was greater in the breast cancer exercise group compared to the breast cancer non-exercise group for three of the four moments tested: isometric flexion (1.0 vs 0.6 Nm; p < 0.05), concentric extension (1.4 vs 0.9 Nm; p < 0.05), and concentric flexion (0.7 vs 0.5 Nm; p < 0.05); isometric extension, was slightly higher in the breast cancer exercise group compared to the breast cancer non- exercise group (2.2 vs 1.8 Nm; p > 0.05). There were no differences between the two breast cancer groups in 6 of the 8 domains of quality of life, with Physical Functioning (92.1 vs 64.3; p < 0.05) and Role Physical (93.6 vs 62.6; p < 0.05), showing higher values for the breast cancer exercise group compared to the breast cancer non-exercise group. Surprisingly, the breast cancer exercise group reported higher on the Mental Health domain (12.6 vs 10.9; p < 0.05) of perceived fatigue compared to the breast cancer non-exercise group. The breast cancer non-exercise group reported higher on the Reduced Activity domain (13.9 vs 12.1; p < 0.05) compared to the breast cancer non-exercise group. There were no differences between these two groups for the remaining domains of perceived fatigue.
Following the 12-week exercise intervention, the healthy control group showed a higher muscle density (75.4 vs 74.0 g/dL; p < 0.05) compared to the breast cancer exercise group. However, the effect of exercise on muscle density was not different between the two groups (p > 0.05). There were no differences between the breast cancer exercise and healthy control groups for either body mass (72.8 vs 65.0 kg; p > 0.05) or body mass index (BMI) (24.9 vs 24.1; p > 0.05). Furthermore, there were no difference s between the two groups for whole body lean mass (44.8 vs 41.6 kg; p > 0.05), whole body fat mass (32.1 vs 26.1 kg; p > 0.05), muscle CSA (69.7 vs 78.9 m²; p > 0.05) or fat CSA (75.0 vs 74.9 cm²; p > 0.05).
Muscle strength was greater in the healthy control group compared to the breast cancer exercise group for three of the four moments tested: isometric extension (2.7 vs 2.2 Nm; p < 0.05), concentric extension (1.7 vs 1.4 Nm; p < 0.05), and concentric flexio n (1.2 vs 0.7 Nm; p < 0.05). For isometric flexion, there was no difference between the two groups (1.0 vs 1.0 Nm; p > 0.05).
The exercising breast cancer group reported higher scores for three of the QoL scales: Physical Functioning (92.1 vs 91.8; p < 0.05), Role Physical (93.6 vs 90.7; p < 0.05) and Vitality (74.1 vs 67.6; p < 0.05), compared to the healthy exercise control group following the 12-week exercise intervention. There were no differences between these two groups for the remaining five quality of life domains. Furthermore, there were no differences between these two groups on any of the domains of perceived fatigue.
The reduction in fat mass, increase in muscle strength, improvements in quality of life and fatigue in the exercising breast cancer group, compared to the breast cancer non- exercise group and healthy exercising women following the intervention, can be regarded as a beneficial effect of resistance exercise. There was no indication from our data that resistance training arrested loss of lean mass in our exercising breast cancer group, an observation that may be related to the small sample size. The gain in muscle strength in the exercising breast cancer group raises questions about the functio na l significance of the loss of lean mass. In conclusion, despite our small sample size, we were able to show improvements in muscle strength, quality of life and fatigue in breast cancer patients (treated specifically with anthracycline/taxane adjuvant chemotherapy) following a 12-week progressive resistance training program in a home-setting. These observations support the use of home-based progressive resistance training in this population. Although not the first study to explore the efficacy of a resistance exercise program in breast cancer survivors, the current study has shown definitive (i.e. dynamometry) improvements in muscle strength and body composition associated with a “low-tech” home-based resistance exercise program over a relatively short period. Related improvements in quality of life and perceived fatigue support the promotion of such a program immediately following the completion chemotherapy treatment.