Pelvic insufficiency fracture after definitive radiotherapy for uterine cervical cancer: retrospective analysis of risk factors

Abstract

The purpose of this study is to determine the incidence, clinical characteristics and risk factors of postradiation pelvic insufficiency fracture (PIF) in women with uterine cervical cancer. We reviewed the medical records of 126 patients who received definitive radiotherapy (RT) for uterine cervical cancer between 2003 and 2009 at our institution. Among them, 99 patients who underwent at least one computed tomography (CT) or magnetic resonance imaging of the pelvis during their follow-up at more than 6 months were included in this analysis. The relationship between the incidence of PIF and several patient- and treatment-related factors was analyzed. The median follow-up period was 21 months. Of the 126 patients, 33 (with a total of 50 lesions) were diagnosed with PIF. The 2-year cumulative incidence was 32%. Univariate analysis showed that age ≥70 years (P= 0.0010), postmenopausal state (P = 0.0013), and lower CT density of bone and bone marrow (P= 0.020) significantly related to PIF. In a multivariate analysis, of the 59 patients whose CT densities were evaluable, lower CT density was the only significant factor associated with PIF (P = 0.0026). In conclusion, postradiation PIFs were detected in a considerable number of patients after definitive RT for cervical cancer. Predisposing factors were older age, postmenopausal state, and decreased density of bone and bone marrow on CT.

Keywords: CT density; adverse event; pelvic insufficiency fracture; radiotherapy; uterine cervical cancer.

Fig. 1.

(A) Transaxial image of an RT-planning CT of a representative case. Area of visually lowest density of bone marrow in the right and left sacrum coincided with each other in this case. CT densitometry shows −87 and −97 HU on the right and left sacral bone marrow, respectively. (B) Transaxial image of a RT-planning CT of the same case as Fig. 1A. L5 lumbar vertebra shows the most homogenous bone marrow density on this slice. CT densitometry shows 72 HU on L5 lumbar vertebra.

Fig. 2.

(A) Cumulative incidence of overall PIF after pelvic radiotherapy for uterine cervical cancer. The 2- and 5-year cumulative incidences of overall PIF were 32% and 63%, respectively. (B) Cumulative incidence of symptomatic PIF. The 2- and 5-year cumulative incidences were 21% and 33%, respectively.

Fig. 3.

Distribution and proportion of PIF in a general anteroposterior/posteroanterior pelvic field after radiotherapy for uterine cervical cancer. Fracture lines and bone necrosis within the irradiated field were counted as PIF.

Fig. 4.

A follow-up CT image obtained 12 months after treatment shows multiple sacral fracture lines (arrows).