Abstract
Objective With the increasing application of radiotherapy for cervical cancer, the incidence of sacral insufficiency fracture (SIF) is increasing gradually. Incorrect or untimely treatment caused by misdiagnosis may lead to serious adverse clinical consequences. This study retrospectively analyzed SIF caused by radiotherapy regarding the appearance and dynamic changes in 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG) positive emission tomography (PET)/computed tomography (CT) images to improve the understanding of SIF. Materials and Methods We retrospectively examined cervical cancer patients who underwent pelvic radiotherapy and 18F-FDG PET/CT between January 2014 and January 2021. Comparative analysis of the imaging performance and follow-up data was conducted. In total, 38 patients with ages ranging from 28 to 81 years (mean age 59.2 ± 10.6 y, median age 56 y) participated in the study. The respective characteristics of the 38 patients were summarized, and diagnosis was confirmed by follow-up changes. Results Twenty-five (65.8%) of the 38 patients suffered from unilateral SIF, and 13 (34.2%) suffered from bilateral SIF. After receiving radiotherapy, SIF first appeared in 3–42 months (median, 13 months). The main 18F-FDG PET/CT manifestations of SIF were increased bone density (35/38, 92.1%), anterior sacral fracture line (28/38, 73.7%), and diffuse or linear uptake patterns parallel to the sacroiliac joint (37/38, 97.3%), with the maximum standard uptake value (SUVmax) ranging from 1.8 to 5.9 (average, 3.1). Follow-up lasted 3–59 months (mean, 14 months). The main changes in SIF were increases in the bone density and high-density range and decreases in the FDG uptake intensity and hypermetabolism range. Three patients had secondary sacral or sacroiliac joint infection (3/38, 7.9%), and 3 patients had secondary fracture and/or pelvic deformation (3/38, 7.9%). Conclusions 18F-FDG PET/CT is an effective technique for diagnosing SIF. A small fracture line in the anterior sacrum and diffuse or linear areas of high density or metabolism parallel to the sacroiliac joint were the characteristic features of SIF. The main changes in SIF were increases in the bone density and high-density range and decreases in the FDG uptake intensity and hypermetabolism range.
Highlights
Insufficiency fracture (IF) is a stress fracture caused by normal or physiological stress acting on bone affected by demineralization or reduced elasticity [1,2,3]. e sacrum, which is part of the posterior ring of the pelvis, is the most common site of IF; the sacrum conducts most of the gravitational force of the body and is an area of bone stress concentration [4]. ere are many causes of IF, such as osteoporosis, radiotherapy, rheumatoid arthritis, and hyperparathyroidism [1, 5, 6]
As 18F-FDG positive emission tomography (PET)/computed tomography (CT) is widely used in the staging and monitoring of malignant tumors, physicians are facing new challenges: what is the performance of 18F-FDG PET/CT in detecting sacral insufficiency fracture (SIF) after radiotherapy? How can SIF be effectively distinguished from malignant bone metastasis in PET/CT images? previous studies have described the performance of bone scans, CT, and magnetic resonance imaging (MRI) in detecting SIF [1, 10, 11], only a few studies have discussed the 18F-FDG PET/CT manifestations of SIF [12,13,14], and no studies have described the dynamic features of SIF. is study was jointly conducted by two hospitals in a large number of patients
Compared with the baseline 18F-FDG PET/CT, we found that the overall range of hypermetabolism was reduced, new hypermetabolism foci developed in some cases; similar results have been found in other studies [12]. is suggests that SIF is a process of continuous bone damage and repair
Summary
Insufficiency fracture (IF) is a stress fracture caused by normal or physiological stress acting on bone affected by demineralization or reduced elasticity [1,2,3]. e sacrum, which is part of the posterior ring of the pelvis, is the most common site of IF; the sacrum conducts most of the gravitational force of the body and is an area of bone stress concentration [4]. ere are many causes of IF, such as osteoporosis, radiotherapy, rheumatoid arthritis, and hyperparathyroidism [1, 5, 6]. Radiotherapy effectively improves the survival of patients, it is the most common cause of sacral insufficiency fracture (SIF) [7, 8]. SIF often causes lower back pain, which is misdiagnosed as bone metastasis in cancer patients, and leads to unnecessary biopsy or antitumor treatment. Previous studies have described the performance of bone scans, CT, and magnetic resonance imaging (MRI) in detecting SIF [1, 10, 11], only a few studies have discussed the 18F-FDG PET/CT manifestations of SIF [12,13,14], and no studies have described the dynamic features of SIF. According to the needs of tumor diagnosis and treatment, patients often require multiple 18F-FDG PET/CTand CTreexaminations, which provide convenient conditions for dynamic observation of the disease
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