Purpose: To quantify microscopic invasion of intrahepatic cholangiocarcinoma (IHC) into nontumor tissue and define the gross tumor volume (GTV)-to-clinical target volume (CTV) expansion necessary for radiotherapy.
Methods and materials: One-hundred IHC patients undergoing radical resection from January 2004 to July 2008 were enrolled in this study. Pathologic and clinical data including maximum tumor diameter, tumor boundary type, TNM stage, histologic grade, tumor markers, and liver enzymes were reviewed. The distance of microinvasion from the tumor boundary was measured by microscopy. The contraction coefficient for tumor measurements in radiographs and slide-mounted tissue was calculated. SPSS15.0 was used for statistical analysis.
Results: Sixty-five patients (65%) exhibited tumor microinvasions. Microinvasions ranged from 0.4-8 mm, with 96% of patients having a microinvasion distance ≤6 mm measured on slide. The radiograph-to-slide contraction coefficient was 82.1%. The degree of microinvasion was correlated with tumor boundary type, TNM stage, histologic grade, and serum levels of carbohydrate antigen 19-9, alanine aminotransferase, aspartate aminotransferase, γ-glutamyltransferase and alkaline phosphatase. To define CTV accurately, we devised a scoring system based on combination of these factors. According to this system, a score ≤1.5 is associated with 96.1% sensitivity in detecting patients with a microextension ≤4.9 mm in radiographs, whereas a score ≥2 has a 95.1% sensitivity in detecting microextension ≤7.9 mm measured on radiograph.
Conclusions: Patients with a score ≤1.5 and ≥2 require a radiographic GTV-to-CTV expansions of 4.9 and 7.9 mm, respectively, to encompass >95% of microinvasions.
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