The Effects of Breast Cancer Surgery on Thoracic Kyphosis and the Correlation Between Supine CT and Standing X-Rays:...

Background/Objectives: Breast cancer surgery can induce postural adaptations that influence spinal alignment. Although previous studies have predominantly addressed coronal deformities such as scoliosis, changes in sagittal alignment, particularly thoracic kyphosis, remain poorly characterized. An increased kyphotic angle has been associated with impaired physical function, emphasizing the importance of assessing sagittal spinal changes after surgery. Although thoracic kyphosis is traditionally measured on standing radiographs, it can also be evaluated using supine chest computed tomography (CT), routinely obtained during postoperative follow-up. This study investigated the impact of breast cancer surgery on thoracic kyphotic angle and assessed the correlation between kyphotic angles measured on supine CT and standing X-rays. Methods: This retrospective study included 185 breast cancer patients who underwent multiple chest CT and whole-spine X-rays. The thoracic kyphotic angle was defined as the Cobb angle from T4 to T12 on sagittal images. Changes in kyphotic angle among the three surgical groups were analyzed using linear mixed-effects models adjusted for age, chemotherapy, radiotherapy, and endocrine treatment. The correlation between supine CT and standing X-ray was analyzed using Pearson's coefficient. Results: The mean follow-up interval was 42.6 ± 6.3 months. The mean angular change was minimal (0.6 ± 2.8°), and no significant effects of time, surgical group, or their interaction were observed. Kyphotic angles measured on standing X-rays strongly correlated with those obtained from supine CT (r = 0.799, p < 0.001), with standing values approximately 7.4° higher. Conclusions: Breast cancer surgery did not significantly alter the thoracic kyphotic angle. Supine CT provides a reliable and practical alternative for the assessment of postoperative kyphosis during follow-up.