Conference Coverage

IMRT bests conventional radiation for soft-tissue sarcomas of the extremities


 

AT THE ASTRO ANNUAL MEETING

ATLANTA – Intensity-modulated radiation therapy proved significantly better than conventional radiation for local control of soft-tissue sarcomas of the extremities, according to new study results, investigators reported at the annual meeting of the American Society for Radiation Oncology.

The 5-year local control rate with intensity-modulated radiation therapy (IMRT) was 92.4%, compared with 85% for external-beam radiation therapy (EBRT), said Dr. Kaled M. Alektiar, a radiation oncologist at Memorial Sloan-Kettering Cancer Center in New York.

The benefits of IMRT were seen despite a preponderance of higher risks in patients treated with IMRT. And, "the morbidity profile, especially for chronic lymphedema of grade 3 or higher, was significantly less," Dr. Alektiar said.

He and his coinvestigators looked at 320 patients who underwent definitive surgery and radiation therapy at Memorial Sloan-Kettering for primary, nonmetastatic soft-tissue sarcomas of the extremities. Of this group, 155 received EBRT with a conventional technique, usually three-dimensional conformal radiation, and 165 patients received IMRT.

Most of the tumors (74.7%) were in the lower extremity, 45.6% were at least 10 cm in diameter, 92.2% were in deep tissue, 82.5% were high grade, and 40% had close or positive surgical margins. The majority of patients (75.9%) received adjuvant chemotherapy.

There were significantly more patients with positive or close margins in the IMRT group than in the conventional EBRT group (47.9% vs. 31.6%; P = .003), and more patients treated with IMRT had high-grade histology tumors, although this difference had only borderline significance (86.7% vs. 78.1%; P =.055).

Additionally, significantly more patients in the IMRT group received preoperative radiation (21.2% vs. 3.2%; P less than .001). Otherwise, the groups were balanced in terms of demographics, tumor size, depth, and use of CT in treatment planning.

The median follow-up was 49.5 months (42 months for patients treated with IMRT, and 87 months for those treated with EBRT). The 5-year local recurrence rates were 7.6% for IMRT and 15% for conventional EBRT. The median time to local recurrence was 18 months in each group.

Eight patients required amputations for salvage, including three in the IMRT cohort and five in the conventional radiation cohort.

In multivariate analysis, three factors that were significantly prognostic for local failure were IMRT (hazard ratio, 0.46; P = .02), age less than 50 years (HR, 0.44; P = .04), and a tumor size of 10 cm or less in the longest dimension (HR, 0.53; P = .05).

Overall survival at 5 years was 69.1% for IMRT and 75.6% for EBRT, a difference that was not significant.

Rates of grade 3 or 4 acute toxicities, including infected and noninfected wound complications and radiation dermatitis, were similar between the groups. Patients treated with IMRT had significantly shorter treatment interruptions, at a mean of 0.8 days, compared with 2.2 days for patients treated with conventional EBRT. Chronic grade 3 or higher lymphedema did not occur in any patients treated with IMRT, compared with four patients treated with conventional EBRT (P = .053).

The study was supported by a grant from the Clinical and Translational Science Center at Weill Cornell Medical College, New York. Dr. Alektiar reported having no relevant financial disclosures.

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