Liposarcoma: outcome and prognostic factors following conservation surgery and radiation therapy.

PURPOSE: Liposarcoma is among the more common types of soft-tissue sarcoma. This retrospective review was performed to determine the outcome and delineate prognostic factors for this disease when treated by conservation surgery and radiation. METHODS AND MATERIALS: Between 1964 and 1992, 112 consecutive patients with liposarcoma were treated with conservation surgery and radiotherapy. Univariate and multivariate statistics were used to evaluate the outcome with local control, metastatic relapse, and survival as end points, and to delineate independently significant prognostic factors.
RESULTS: Preoperative radiation to a mean dose of 50 Gy was used in 36 patients and postoperative radiation to a mean dose of 61 Gy was used in 76 patients. At a median follow-up of 9 years (range 2-25), 34 patients (30%) developed disease progression at some site. Local recurrence developed in 14 patients (13%), and the actuarial local relapse rate was 13% at 10 years. Metastases developed in 23 patients (21%) with an actuarial metastatic rate of 23% at 10 years. Five-, 10-, and 15-year survival rates were 79%, 69%, and 61%, respectively. The most important factor influencing outcome--whether local control, metastases, or survival--was tumor histologic subtype. Well-differentiated (15 patients) and myxoid (including round cell) (71 patients) subtypes had a local control rate exceeding 90% at 10 years. No patient with well-differentiated liposarcoma developed metastases. The actuarial metastatic rate for myxoid tumors was 22% at 10 years and was higher for large than small tumors. The pattern of metastases for this variant was atypical with a preponderance of extrapulmonary sites. Pleomorphic liposarcoma (26 patients) was a highly malignant tumor with a high local recurrence rate of 37% and a metastatic rate of 41% at 10 years. Larger pleomorphic tumors had a significantly higher metastatic rate than smaller ones. These biologic factors were reflected in progressively decreasing 10-year survival rates from 87% for well-differentiated lesions, through 76% for myxoid tumors, to 39% for pleomorphic tumors. Although other factors such as positive resection margins and prior local recurrence were also independently significant determinants of outcome, histology was the overriding factor.
CONCLUSION: Liposarcoma is a highly pleomorphic disease whose outcome is greatly determined by its histologic subtype: so greatly that results reported without histologic stratification are likely meaningless. Conservation surgery and radiation achieve excellent local results and with relatively little metastatic risk for patients with well-differentiated and myxoid liposarcomas. The same treatment strategy appears appropriate for pleomorphic liposarcoma, but with a much smaller expectation of a satisfactory outcome. The development of effective systemic therapy is an important goal for this variant of liposarcoma.