IMRT reduced recurrence rates in primary soft tissue sarcoma
Patients with primary soft tissue sarcomas of the extremity who underwent intensity-modulated radiation therapy experienced significantly reduced rates of local recurrence compared with those who underwent conventional external beam radiation therapy, according to study results.
Adjuvant radiation therapy — known to improve local control for soft tissue sarcoma of the extremity following limb-sparing surgery — may be given via brachytherapy or external-beam radiation therapy (EBRT). EBRT options include conventional EBRT, intensity-modulated radiation therapy (IMRT) and proton therapy.
The use of IMRT in the treatment of extremity soft-tissue sarcoma is limited, but surveys suggest it is increasing, according to Michael R. Folkert, MD, radiation oncology resident in the department of radiation oncology at Memorial Sloan Kettering Cancer Center, and colleagues.
Due to encouraging results with IMRT, Memorial Sloan Kettering Cancer Center has started increasing its use of IMRT rather than EBRT. However, no direct comparison between the two approaches has been reported.
In the current study, Folkert and colleagues evaluated outcomes of 165 patients who underwent IMRT between 2002 and 2010, then compared results with those from 154 patients who underwent conventional EBRT as far back as 1996.
Treatment groups were comparable in terms of tumor location, histology, tumor size, depth and chemotherapy use.
Patients in the IMRT group were more likely to be older (P=.08), have more tumors with high-grade histology (P=.05), and have close (<1 mm) or positive margins (P=.04). They also were more likely to have received preoperative radiation (P=.001) and nerve manipulation (P=.04).
Median follow-up was 90 months in the conventional EBRT arm and 42 months in the IMRT arm.
Results showed patients who underwent IMRT experienced a lower rate of 5-year local recurrence than those who underwent conventional EBRT (7.6% vs. 15.1%; P=.05). After adjustments for patient age and tumor size, IMRT retained significance as an independent predictor for reduced local recurrence (HR=0.46; 95% CI, 0.24-0.89).
Median time to local recurrence was comparable between the IMRT group (18 months; range, 9-33) and the conventional EBRT group (18 months; range, 2-69).
The rate of 5-year DFS was higher in the IMRT group (57.2% vs. 56.3%), but the rate of 5-year OS was higher in the conventional EBRT group (75.6% vs. 68.1%).
Disclosure: The researchers report employment/leadership positions with and stock ownership in ZIOPHARM Oncology.