Radiotherapy-Associated Pelvic Insufficiency Fracture Treated by Romosozumab: Course of CT Attenuations at L1 and L5.

Pelvic radiation therapy (RT) is a risk factor for pelvic insufficiency fracture, which may be accompanied by significant pain, decreased self-sufficiency, and impaired mobility. Assessment of bone density with "opportunistic" computed tomography (CT) attenuation of the L1 vertebral body can be used as a surrogate for dual-energy x-ray absorptiometry (DXA) scan and potentially be useful to follow bone changes in cancer patients who undergo surveillance CT imaging. The following is a case of a 60-year-old female who suffered a pelvic insufficiency fracture, after receiving chemotherapy and pelvic RT for endometrial cancer, for which she was treated with romosozumab, a sclerostin inhibitor used for postmenopausal women at high risk for insufficiency or fragility fracture. CT attenuation of the L1 and L5 vertebral bodies were measured prior to chemoradiation therapy, post-therapy, and before and after treatment with romosozumab. Pelvic RT was associated with declining CT attenuation, greater in magnitude at L5 vs L1 vertebral body, while treatment with romosozumab was associated with increase to baseline at L1, and improvement but not return to baseline at L5.