Incidence, characteristics, and exploratory analysis of factors associated with pelvic osteitis/osteoradionecrosis after radiotherapy for cervical cancer: a single-center retrospective cohort study with an unmatched case-control analysis.

Background: Pelvic radiotherapy is the standard treatment for locally advanced cervical cancer and has substantially improved patient survival. As survival has increased, late radiation-related complications have become increasingly important. Radiation osteitis (RO) and osteoradionecrosis (ORN) are uncommon but potentially disabling forms of radiation-induced pelvic bone injury. However, most previous studies have focused on pelvic insufficiency fractures (PIFs) rather than pelvic RO/ORN. Consequently, the incidence, clinical characteristics, imaging features, and risk factors of pelvic RO/ORN remain poorly defined, particularly in patients treated with contemporary intensity-modulated radiotherapy (IMRT). This study aimed to investigate the incidence, clinical and imaging characteristics, and potential risk factors of pelvic RO/ORN in cervical cancer patients receiving pelvic radiotherapy. Methods: A retrospective cohort study with an unmatched case-control analysis was conducted among 308 cervical cancer patients treated with pelvic radiotherapy between January 2015 and December 2021. After follow-up and imaging review, 28 patients diagnosed with pelvic RO/ORN were identified. Fifty-six controls were selected by simple random sampling without replacement from the remaining cohort members in whom RO/ORN was not identified during available follow-up. Clinical characteristics, tumor features, and treatment-related variables were compared between groups. Univariable and multivariable logistic regression analyses were exploratory. Results: Pelvic RO/ORN was identified in 28 of 308 patients, corresponding to an incidence of 9.1%. The median time to diagnosis was 22.5 months [interquartile range (IQR), 15.5-33.0 months] after radiotherapy. The sacrum/sacroiliac region and ilium were the most frequently involved sites. Typical imaging findings included mixed osteolytic and sclerotic lesions, irregular cortical disruption, and inflammatory changes in adjacent soft tissues. Seventeen patients (60.7%) had pelvic or hip pain or movement-related symptoms, whereas 11 (39.3%) were identified on surveillance imaging without apparent symptoms. No statistically significant between-group differences were observed for the clinical and treatment variables examined (all P>0.05). Exploratory multivariable logistic regression did not identify clear independent associations in this dataset. Conclusions: Pelvic RO/ORN is a clinically relevant late effect of pelvic radiotherapy for cervical cancer. In this dataset, no clear predictors were identified among the clinical and treatment variables examined; this negative finding should be interpreted cautiously because the number of events was limited and patient-specific pelvic bone dosimetry and bone-health measures were unavailable. Future risk assessment should move beyond conventional clinical parameters by integrating dosimetric, imaging, and biological markers to clarify risk factors and the value of earlier detection.