Gross tumor volume delineation in patients undergoing breast–conserving surgery: a comparative study of preoperative magnetic resonance imaging, postoperative specimen, and lumpectomy cavity based on surgical clips

Objective To explore the gross tumor volume (GTV) difference and correlation between preoperative magnetic resonance imaging (MRI), postoperative specimen, and lumpectomy cavity based on surgical clips. Methods Fifty patients with breast cancer undergoing breast-conserving surgery were enrolled as subjects from 2014 to 2015. GTVMRI was defined as tumor volume based on preoperative MRI scans, while GTVMRI+ 1 was defined as GTVMRI plus a 1.0-cm margin. GTVES was defined as the volume of excised specimen, while GTVPAT was defined as the pathological volume of the specimen. GTVTB was defined as tumor volume based on lumpectomy cavity localized by surgical clips on computed tomography images. Comparison between any two GTVs was made by Friedman test and Wilcoxon test. A correlation analysis was made by Spearman rank correlation. Results The median values of GTVMRI, GTVMRI+ 1, GTVPAT, GTVES, and GTVTB were 0.97(0.01-6.88), 12.58(3.90-34.13), 0.97(0.01-2.36), 15.46(1.15-70.69), and 19.24(4.72-54.33) cm3, respectively. There were no significant differences between GTVMRI and GTVPAT, between GTVMRI+ 1 and GTVES, and between GTVES and GTVTB (P=0.188, 0.07, 0.264). Neither GTVES nor GTVTB was correlated with GTVMRI(P=0.071, 0.378) or GTVMRI+ 1(P=0.068, 0.375). GTVTB was positively correlated with GTVES (r=0.488, P=0.004). Conclusions For patients undergoing breast-conserving therapy, during lumpectomy guided by palpation rather than imaging, neither the volume of excised specimen nor lumpectomy cavity based on surgical clips are correlated with tumor volume based on preoperative MRI. Key words: Magnetic resonance imaging; Breast conservation therapy; Excised specimen; Lumpectomy cavity; Primary tumor