Increased Risk of Pelvic Fracture after Radiation Therapy in Rectal Cancer Survivors: A Propensity Matched Study

Abstract

High-dose pelvic radiation is associated with increased pelvic fracture risk in cervical cancer and prostate cancer patients. However, it is not clear whether rectal radiotherapy would increase pelvic fracture risk in rectal cancer survivors. Rectal cancer patients who underwent curative surgery between 1996 to 2011 in Taiwan were retrospectively studied. Age, sex, comorbidities, Charlson comorbidity score, osteoporosis status, previous fracture status, radiotherapy, chemotherapy, and target therapy data were collected from National Health Insurance Research Database (NHIRD) of Taiwan. ICD-9 Codes 808, 805.4-805.7, 806.4-806.7, and 820 (including pelvic, sacrum, lumbar vertebral fracture, and femoral neck fracture) were defined as pelvic fracture in this study. Propensity scores for radiotherapy for each patient were used to perform one-to-one match between radiotherapy group and non-radiotherapy group. Incidences of pelvic fracture and arm fracture (as a control) were compared by multivariate Cox regression. Demographic sub-group analyses were also studied. Of the 32689 patients studied, 7807 patients (23.9%) received radiotherapy, and 1616 patients suffered from pelvic fracture (incidence: 4.9%). After propensity score matching, 6952 patients in the radiotherapy group and 6952 patients in the non-radiotherapy group were analyzed. Radiotherapy was associated with increased risk of pelvic fracture in multi-variate Cox model (hazard ratio(HR): 1.216, 95% CI: 1.017-1.454, p =0.032), but was not associated with increased risk of arm fracture (HR: 1.014, 95% CI: 0.819-1.254, p=0.901). Previous fracture, older age, and female sex also showed increased risk of pelvic fracture and arm fracture. Subgroup analyses revealed radiotherapy was associated with higher risk of pelvic fracture in four types of patients: age over 60 years old (HR: 1.235, 95% CI: 1.021-1.495), females (HR: 1.39, 95% CI:1.091-1.771), those without previous fractures (HR: 1.257, 95% CI:1.02-1.55), and those who received chemotherapy (HR: 1.382, 95% CI: 1.049-1.681). Increased risk of pelvic fracture is noted in rectal cancer survivors who had received radiotherapy, especially in those who are elderly, female, without previous fracture experiences, and with chemotherapy.Abstract 2382; TableMultivariate Cox regression after propensity score matchPelvic fractureArm fractureHR (95% CI)P valueHR (95% CI)P valueRadiotherapy1.216 (1.017-1.454)0.0321.014 (0.819-1.254)0.901Osteoporosis1.264 (1.002-1.595)0.0481.009 (0.740-1.376)0.955Previous fracture2.190 (1.777-2.712)<0.0011.969 (1.499-2.586)<0.001Age (>=60 y vs. <60 y)1.085 (1.075-1.096)<0.0011.024 (1.014-1.034)<0.001Sex (Male vs. Female)0.498 (0.414-0.600)<0.0010.393 (0.315-0.491)<0.001 Open table in a new tab