What is the prevalence of symptomatic or asymptomatic femoral head osteonecrosis in patients previously treated with chemoradiation? A magnetic resonance study of anal cancer patients.

It is generally assumed that femoral head osteonecrosis (FHO) is a serious but rare complication of pelvic radiotherapy. A review of the literature carried out by the authors indicates a prevalence of 4/763 (95% confidence interval 0.1%-1.3%). A recent publication has suggested that the prevalence of symptomatic FHO may be much greater than previously assumed as a result of sensitization of bone to radiation by concomitant treatment with chemotherapy. Magnetic resonance imaging (MRI) is currently the most sensitive modality for detecting and confirming symptomatic or asymptomatic FHO of any aetiology. The aim of this study therefore was to assess the prevalence of symptomatic and asymptomatic FHO in patients previously treated for anal cancer by chemoradiation (CRT). The hips of 34 currently disease-free individuals (11 men and 23 women; median age 67 years, range 32-86) were scanned using a coronal T1-weighted sequence. The images were assessed for evidence of FHO. The median time of scanning after the end of CRT was 35 months (range 6-107). No cases (0/34) of symptomatic or asymptomatic FHO were detected in these patients. Given the established sensitivity of MRI in the detection of FHO, it is concluded that changes indicative of osteonecrosis were uncommon after CRT in the current cohort of patients. Recent evidence from the literature suggests, however, that elderly females are at greatest risk of developing FHO after CRT.