Value of MDCT in preoperative local staging of rectal cancer for predicting the necessity for neoadjuvant radiochemotherapy.

Purpose: Neoadjuvant therapy may reduce local rectal cancer recurrence after total mesorectum extirpation. This study was performed to assess whether multi-detector row CT (MDCT) is capable of reliably differentiating UICC I (surgery) from UICC II-IV (neoadjuvant therapy).

Materials And Methods: 29 patients underwent preoperative MDCT of the abdomen in a portal venous phase. Two blinded readers independently evaluated the datasets on a dedicated workstation using axial and coronal reformations. Local tumor extension (T), nodal status (N) and distant metastases (M) were evaluated and the UICC stage was determined. Findings were correlated with postoperative histology.

Results: Histologically, 9 patients were UICC I; 20 UICC > I (II: 7; III: 11; IV: 2). Reader 1 correctly identified 3 / 9 as UICC I, overstaged 6 / 9, and correctly staged 20 / 20 as UICC > I. Reader 2 correctly identified 4 / 9 as UICC I, overstaged 5 / 9, understaged 4 / 20 and correctly staged 16 / 20 as UICC > I (PPV UICC I 100 % [50 %] reader 1 [reader 2], NPV 77 % [76 %], accuracy 79 % [69 %]). Reasons for overstaging by reader 1 (reader 2) included false-positive lymph nodes (LN) in 5 (5), overgrading T 1 tumors as T 3 in 1(0), and T overgrading in 4 / 5 (2 / 5) patients with false-positive LN.

Conclusion: MDCT failed to reliably identify UICC I in rectal cancer patients. Therefore, a strategy based solely on MDCT to identify patients who would benefit from neoadjuvant therapy does not seem appropriate.