Femoral Fracture in Primary Soft-Tissue Sarcoma of the Thigh and Groin Treated with Intensity-Modulated Radiation Therapy: Observed versus Expected Risk
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This study was designed to compare the observed risk of femoral fracture in primary soft-tissue sarcoma (STS) of the thigh/groin treated with intensity-modulated radiation therapy (IMRT) to expected risk calculated using the Princess Margaret Hospital (PMH) nomogram.
Expected femoral fracture risk was calculated by using the PMH nomogram. Cumulative risk of fracture was estimated by using Kaplan–Meier statistics. Prognostic factors were assessed with univariate and multivariate analysis using Cox’s stepwise regression.
Between February 2002 and December 2010, 92 consecutive eligible patients were assessed. Median follow-up was 73 months (106 months in surviving patients). IMRT was delivered preoperatively (50 Gy) in 13 (14%) patients and postoperatively in 79 (86%) patients (median dose, 63 Gy; range, 59.4–66.6 Gy). The observed crude risk of fractures was 6.5% compared with 25.6% expected risk from the nomogram; the cumulative risk of fracture using IMRT at 5 years was 6.7% (95% CI 2.8–16.0%). The median time to fracture was 23 months (range, 6.9–88.6). Significant predictors of fracture on univariate analysis were age ≥ 60 years (p = 0.03), tumor location in the anterior thigh (p = 0.008), and periosteal stripping to > 20 cm (p < 0.0001). On multivariate analysis, age ≥ 60 years and periosteal stripping > 20 cm retained significance (p = 0.04 and p = 0.009, respectively).
In this study, the cumulative risk of femur fracture in patients treated with IMRT (6.7%) is less than the expected risk using the PMH nomogram (25.6%). Established predictors of femur fracture, such as gender, tumor size, and dose of RT, seem to have less impact on fracture risk when using IMRT.
This research was supported by the NIH/NCI Grant P50 CA140146 (SPORE in Soft Tissue Sarcoma) and the NIH/NCI Cancer Center Support Grant P30 CA008748.
This work was supported by the National Cancer Institute via the SPORE in Soft Tissue Sarcoma (P50 CA140146 to SS) and the Cancer Center Support Grant P30 CA008748. Michael R. Folkert receives travel funding from Varian, Inc. and research support from Augmenix, Inc. None of the other authors have conflicts to disclose. None of the authors have a personal or institutional financial interest in the materials or devices described in this submission.
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