A nomogram to predict postresection 5-year overall survival for patients with uterine leiomyosarcoma†

Uterine leiomyosarcoma (LMS) is a rare neoplasm with an annual incidence of 0.64 per 100,000 women.1 It accounts for <5% of all uterine malignancies and approximately 30% of all uterine sarcomas.2 The disease is characterized by a propensity for early hematogenous spread, leading to high local and distant failure rates.3-5 In contrast to the much more common uterine adenocarcinoma, lymphatic spread is a rare event, and the overall prognosis is poor.6 Surgical resection, including hysterectomy and bilateral salpingo-oophorectomy, is the recommended initial treatment strategy. Although most frequently diagnosed while still confined to the uterus, the clinical course of LMS is difficult to predict. To date, no adjuvant treatment strategies have demonstrated a survival benefit. Current staging systems fail to identify which patients are at highest risk for death; thus, it is difficult to select patients in whom to test potentially beneficial adjuvant strategies.7-10 Until recently, the rarity of this disease hampered the development of a uterine LMS-specific staging system. Physicians used a modification of the 1988 International Federation of Gynecology and Obstetrics (FIGO) staging system,11 an organ-based staging system that was developed primarily for the staging of uterine endometrial adenocarcinomas. Alternatively, the American Joint Committee on Cancer (AJCC) uses a separate staging system specifically for soft tissue sarcomas. AJCC is a compartment-based, mixed clinical-pathologic staging system that, among other variables, includes information on tumor size and grade. However, the AJCC system is used primarily for the staging of soft tissue sarcomas of the extremity or trunk and has limited value for the staging of visceral tumors. The predictive accuracy of both the FIGO and AJCC staging systems for patients with uterine LMS has been assessed and compared.5,12 The strength of the FIGO staging system was its ability to identify patients with the poorest prognosis, whereas the strength of AJCC was its ability to identify patients with a better prognosis. However, significant prognostic overlap between stages was observed in both staging systems. Furthermore, because uterine LMS is diagnosed most frequently while it is still confined to the uterus and is predominantly high-grade in nature, the traditional staging systems tend to group most patients within certain stages (ie, stage I in FIGO and stage III in AJCC), falsely suggesting prognostic homogeneity in a highly heterogeneous group of patients. These findings implicate an urgent need for a more robust prognostic model for patients with uterine LMS. Recognizing the shortcomings of the traditionally used staging systems, FIGO recently developed a new classification specifically for uterine LMS to include variables such as tumor size, extrauterine spread, and invasion of abdominal tissues.13 Apart from disease stage, other reported potentially important prognostic factors in patients with uterine LMS include age, mitotic index (MI), and lymphovascular invasion (LVI), none of which are incorporated into the currently used staging systems.14-17 The purpose of the current study was to combine both the AJCC and FIGO stage-defining variables with other prognostic factors and develop a novel uterine LMS-specific nomogram to predict postresection 5-year overall survival (OS).