Modified staging system for extremity soft tissue sarcomas.

Abstract

The establishment of a universally acceptable staging system for soft tissue sarcomas has been hampered by the low incidence, various grading systems, and lack of consensus regarding the value of different prognostic factors. We aimed to evaluate prognostic factors in patients with extremity soft tissue sarcomas and to test the validity of the AJCC/UICC staging system. Prospectively collected data from 316 previously untreated patients with primary extremity soft tissue sarcomas treated at a single institution between 1989 and 1995 were studied. The influence of clinical and pathological factors on local recurrence, distant metastasis, and disease-specific survival was analyzed by univariate and multivariate techniques. Large tumor size and high histological grade were independent adverse prognostic factors for distant metastasis. Large size, high grade, and positive microscopic surgical margins were independent adverse prognostic factors, and liposarcoma histology was an independent favorable prognostic factor for disease-specific survival. Within each histological grade, there was a progressive decline in survival with increasing tumor size, as reflected by an almost linear increase in hazard ratios. Similarly, there was a progressive fall in survival with increasing grade within each size group (<5 cm, 5 to 10 cm, 10 to 15 cm, and > 15 cm). AJCC staging did not correlate well with prognosis. Survival for intermediate-grade tumors smaller than 5 cm (stage IIA) was better than that for low-grade tumors larger than 5 cm (stage IB) (86% vs. 73%). Survival for high-grade tumors smaller than 5 cm (stage IIIA) was better than that for intermediate-grade tumors larger than 5 cm (stage IIB) (72% vs. 57%). A modified staging system was formulated based on the additive influence of size and grade on the estimated hazard ratios for disease-specific survival, as follows: stage IA, G1T1; stage IB, G1T2 or G2T1; stage IIA, G1T3 or G2T2 or G3T1; stage IIB, G1T4 or G2T3 or G3T2; stage IIIA, G2T4 or G3T3; stage IIIB, G3T4; and stage IV, M1 (G1, G2, G3 = low, intermediate, and high grade; T1, T2, T3, T4 = tumor size < 5 cm, 5-10 cm, 10-15 cm, and > 15 cm, respectively). The 5-year disease-specific survivals of stages IA, IB, IIA, IIB, IIIA, and IIIB were 100%, 83%, 74%, 61%, 39%, and 18%, respectively. The 5-year disease-specific survival for stages I, II, III, and IV were 90%, 67%, 31%, and 6% respectively. The survival difference between each stage was statistically significant (P < .001). Histological grade and tumor size are equally important determinants of distant metastases and survival. The AJCC/UICC staging system is based primarily on the grade of the tumor, with size used to subgroup each stage. A staging system for extremity soft tissue sarcomas with equal emphasis on grade and size is proposed that correlates extremely well with prognosis.