External validation of a nomogram predicting overall survival (OS) of women with uterine leiomyosarcoma (ULMS).

Abstract

5090 Background: A nomogram for predicting OS of women with ULMS was developed , given the poor prognostic performance of FIGO and AJCC staging systems. We aimed to determine the validity of the ULMS nomogram using independent, external cohorts. Methods: The ULMS nomogram incorporates 7 clinical characteristics: age at diagnosis, tumor size, grade, involvement of cervix, locoregional metastases (direct extrauterine spread, locoregional lymph node), distant metastases, and mitotic index (per 10 HPF) to predict OS following primary surgery. Two independent cohorts from sarcoma centers (1 US, 1 Europe) were included. Eligible women were treated at the institutions (1994-2010) and had undergone hysterectomy. Women with locally advanced or metastatic disease who underwent more extensive surgery were included if the primary tumor (uterus) was resected. Women who previously underwent resection of the primary tumor or recurrences at other institutions were included if they received followup care at 1 of the centers. Women who presented with unresectable disease who never underwent surgery and those with insufficient information on any of the nomogram variables were excluded. Results: 187 women with ULMS were identified who met the above criteria (median age 51 yrs, median tumor size 9 cm, median mitotic index 20). Tumors were generally high grade (88%), FIGO stage I-II (61%) without cervical involvement (93%) and without locoregional (77%) or distant metastases (83%). Median and 5-yr OS rates were 4.5 (95% CI 3.2-5.3) yrs and 46%, respectively; 65 women (35%) were alive at last follow up. The nomogram concordance index was 0.67(SE=0.02) which was as high as the concordance index from the initial cohort used for nomogram development. The concordance between actual OS and nomogram predictions suggests excellent calibration of the nomogram in the validation cohort. Predictions were within 1% of actual 5-yr OS rates, except for the patients with a 5-yr OS rate of greater than 0.68. Conclusions: The ULMS nomogram was externally validated and can be generalized to independent cohorts. The nomogram provides a more individualized and accurate estimation of OS of women diagnosed with ULMS following primary surgery.