Postoperative Radiotherapy Breast Cancer Treatment: Musculoskeletal and Functional Implications
2023-09
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Postoperative Radiotherapy Breast Cancer Treatment: Musculoskeletal and Functional Implications
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2023-09
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ABSTRACT Purpose/Hypotheses: The overall purpose of this study was to better understand the effect of post-lumpectomy radiation therapy (RT) on skeletal muscle morphology, shoulder kinematics, and shoulder function following treatment for unilateral breast cancer. We hypothesized that within the same breast cancer survivor, the affected (treated) side would demonstrate significantly different shoulder kinematics and skeletal muscle morphology than the unaffected (untreated) side. We also hypothesized that RT dose delivered to specific muscles within the radiation field would adversely affect self-reported shoulder function. A small study was first performed on healthy volunteers to determine intra-rater reliability of a novel method of skeletal muscle B-mode ultrasonography (US) to evaluate echo intensity (EI) and cross-sectional area (CSA) of three muscles within the radiation field that have the potential to affect shoulder function. Number of Participants: 31 (5 healthy volunteers for US reliability, 26 breast cancer survivors for main study) Materials and Methods: This was a single center, non-therapeutic, observational cross-sectional study with two parts. First, 5 healthy volunteers participated in the US reliability study which involved three repeated measures of the pectoralis major (PMaj), pectoralis minor (PMin), and serratus anterior (SA) bilaterally. Second, 26 breast cancer survivors who were at least 1-year post-completion of RT following lumpectomy plus sentinel lymph node biopsy for the treatment of unilateral breast cancer then participated in the main study. Three-dimensional kinematic data were collected using electromagnetic sensors during forward shoulder flexion and abduction. Musculoskeletal US was used to determine skeletal muscle CSA and EI of the PMaj, PMin, and SA muscles of the treated and untreated sides. Radiation dose analyses were performed for those same 3 muscles using pre-existing computed tomography radiation simulation scans. The Penn Shoulder Score (PSS) and a custom questionnaire were also given to participants. Data were analyzed using Wilcoxon rank sum tests to determine difference across sides and groups, Spearman correlation to examine associations between variables, and multiple linear regression to examine covariate effects. Ultrasound intrarater reliability was performed on the healthy participants using intraclass correlation coefficient (ICC) analysis. Statistical significance cutoff value was set at 0.05 for all tests. Results: PMaj and PMin CSA and EI were reliable (ICC > 0.70) and used in the breast cancer survivor study. SA CSA and EI were not reliable (ICC < 0.7) and were used in the main study as exploratory analyses only. Breast cancer survivors demonstrated more sternoclavicular elevation during arm elevation on their affected side vs. their unaffected side. No significant differences existed between the affected and unaffected sides for other shoulder kinematic variables nor for ultrasound EI and CSA. In general, Penn Shoulder Score values were high, but a few specific functional movements were more commonly noted as being difficult which has clinical implications. Some PMin, PMaj, and SA radiation values were significantly correlated with multiple aspects of the PSS (total score and subscales). Trends were found for the PMin radiation dose and total radiation dose to affect the PSS, although correction for multiple testing made these statistically insignificant. Conclusions: Our data suggests that there may be a significant effect of postoperative RT on shoulder function in breast cancer survivors after unilateral lumpectomy and sentinel lymph node biopsy. Kinematic analysis demonstrated increased clavicle elevation on the affected side vs the unaffected side during arm elevation, but clinical relevance is uncertain. B-mode US was a reliable method of quantifying PMaj and PMin CSA and EI, but it was not reliable for the SA. B-mode US may not be sensitive enough to detect significant differences in EI and CSA in these muscles following RT. The PMaj, PMin, and SA receive a significant amount of radiation during treatment which may affect patient-reported shoulder pain. Although PSS scores were generally high, participants consistently reported ‘some difficulty’ with certain functional tasks that highlight the specific impairments many breast cancer survivors have following treatment. Additionally, breast cancer survivors complained not just of ‘shoulder pain’ but also stiffness, tightness, achiness, and other impairments in their shoulder, chest wall, and arm that need to be recognized and addressed by medical providers. This research demonstrates potential relationships between adjuvant RT and shoulder function which need to be further investigated to provide breast cancer survivors with the highest quality of life possible.
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University of Minnesota Ph.D. dissertation. September 2023. Major: Rehabilitation Science. Advisor: Linda Koehler. 1 computer file (PDF); ix, 184 pages.
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Braudy, Renata. (2023). Postoperative Radiotherapy Breast Cancer Treatment: Musculoskeletal and Functional Implications. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/259689.
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