7%) were men. Tumor locations included the stomach, small intestine, and rectum in 48 (80%), 11 (18.3%), and 1 (1.7%) patient, respectively. The median tumor size was 3.8 cm (range, 1.6-20 cm). The median duration of follow-up for patients in this series was 4.1 years (range 0.1-12.8 years), with 6 of 60 patients experiencing recurrence. Five of six patients had disease recurrence ref 1 in the liver, and another had local intrapelvic recurrence. All of these recurrences were detected by follow-up CT scan, with 4 of the recurrence events occurring less than 1 year after surgery. Three patients were lost to follow-up before 2 years. All 3 patients lost to follow-up had very low- or low-risk tumors. According to the NIH criteria, 34 (56.6%), 13 (21.7%), and 13 (21.

7%) tumors were classified as very low- or low-, intermediate-, and high-risk, respectively. According to the AFIP criteria, 3 (5.0%), 35 (58.3%), 13 (21.7%), and 9 (15%) tumors were classified as unknown, very low or low, moderate, and high risk, respectively. In the univariate analysis, size and the mitotic index predicted RFS (p = 0.002). When correlating recurrence with tumor location, a trend toward statistical significance became evident (p = 0.051). Table 2 Characteristics of 60 patients with primary resectable GISTs RFS was 93.0% (SE 0.034%), and 89.9% (SE 0.045%) after 2 and 5 years, respectively (Figure (Figure2).2). In our series, the 2-year and 5-year RFS was better than that reported previously. RFS-classified risk groups according to the NIH and AFIP criteria are shown in Figure Figure3.3.

Recurrence events were observed only in the groups classified as high risk by either set of criteria. Figure 2 Recurrence-free survival of total patients. Kaplan-Meier estimates of the recurrence-free survival of patients with primary GIST after complete surgical resection. Figure 3 Recurrence-free survival classified using commonly used criteria. A. Kaplan-Meier estimates of recurrence-free survival of primary resectable GIST patients classified according to NIH criteria. B. Kaplan-Meier estimates of recurrence-free survival of … Next, we estimated the discriminatory capability of the nomogram by using the C index. The C index of the nomogram prediction for all patients was 0.96, which was adequately acceptable. The C indices of the nomogram predictions excluding the low-risk subgroup and limited to only the high-risk subgroup were 0.

91 and 0.65, respectively. Therefore, in 65% of the cases, the nomogram correctly predicted the order of outcome between 2 randomly selected patients who were classified as high-risk according to either the NIH or AFIP criteria. A calibration test was performed to estimate the accuracy of the RFS predicted by the nomogram. Calibration of the nomogram-predicted RFS tended to overestimate GSK-3 recurrence compared with the Kaplan-Meier-observed RFS (Figure (Figure44). Figure 4 Calibration of nomogram-predicted recurrence-free survival (RFS).