In early studies, accuracy of CT in predicting pathological T stage after radiotherapy was low (37%) but more accurate in the identification of involved circumferential resection margin (71%) [67]. Other studies demonstrated higher accuracy of T stage, up to 61% and CT correlation with pathologic tumor regression, with frequent overstaging due to residual fibrotic change that could not be distinguished from tumor on CT [68]. Nodal involvement was difficult to assess by CT, although change in nodal size could be appreciated, with one early study demonstrating a sensitivity of 56% and a specificity of 74% for nodal involvement [69]. Staging of Colorectal Cancer More recent studies have supported these earlier conclusions, noting that CT restaging was able to document overall response versus nonresponse to neoadjuvant CRT with limited ability to predict pathologic T and N stage at surgical resection; for example, a study of 270 patients receiving CT, MRI, and US restaging revealed 45% accuracy for CT in predicting specific pT stage and 66% accuracy for pN stage [70]. Two surgical cohorts concluded that local restaging CT prompted 0% to 4% change in surgical management of LARC postneoadjuvant CRT and was mostly helpful in the setting of metastatic disease [71,72]. For lymph node involvement, like all modalities that rely primarily on size as determinant of involvement (eg, TRUS and MRI), CT remains relatively nonspecific for N-stage determination. There is little agreement on the critical cut-off diameter to determine if lymph nodes are involved in the disease process before or after neoadjuvant treatment. Nodal size is not seen as a predictor of nodal status at surgery [8,23]. Accuracies for CT detection of lymph node stage range from 56% to 84% [19,20,24-26]. CT Colonography There is no relevant literature regarding the use of CT colonography in the restaging evaluation rectal cancer postneoadjuvant CRT.
Staging of Colorectal Cancer. In early studies, accuracy of CT in predicting pathological T stage after radiotherapy was low (37%) but more accurate in the identification of involved circumferential resection margin (71%) [67]. Other studies demonstrated higher accuracy of T stage, up to 61% and CT correlation with pathologic tumor regression, with frequent overstaging due to residual fibrotic change that could not be distinguished from tumor on CT [68]. Nodal involvement was difficult to assess by CT, although change in nodal size could be appreciated, with one early study demonstrating a sensitivity of 56% and a specificity of 74% for nodal involvement [69]. Staging of Colorectal Cancer More recent studies have supported these earlier conclusions, noting that CT restaging was able to document overall response versus nonresponse to neoadjuvant CRT with limited ability to predict pathologic T and N stage at surgical resection; for example, a study of 270 patients receiving CT, MRI, and US restaging revealed 45% accuracy for CT in predicting specific pT stage and 66% accuracy for pN stage [70]. Two surgical cohorts concluded that local restaging CT prompted 0% to 4% change in surgical management of LARC postneoadjuvant CRT and was mostly helpful in the setting of metastatic disease [71,72]. For lymph node involvement, like all modalities that rely primarily on size as determinant of involvement (eg, TRUS and MRI), CT remains relatively nonspecific for N-stage determination. There is little agreement on the critical cut-off diameter to determine if lymph nodes are involved in the disease process before or after neoadjuvant treatment. Nodal size is not seen as a predictor of nodal status at surgery [8,23]. Accuracies for CT detection of lymph node stage range from 56% to 84% [19,20,24-26]. CT Colonography There is no relevant literature regarding the use of CT colonography in the restaging evaluation rectal cancer postneoadjuvant CRT.