Beomseok Sohn MD, Presenter: Nothing to Disclose

Chansik An MD, Abstract Co-Author: Nothing to Disclose

Joonseok Lim MD, Abstract Co-Author: Nothing to Disclose

Myeong-Jin Kim MD, PhD, Abstract Co-Author: Nothing to Disclose

To minimize the false-negative rate (FNR) of preoperative MRI in the diagnosis of lymph node (LN) metastasis in patients with clinical T1 or T2 rectal cancer. Local excision can reduce the morbidities from radical surgery, but has shown high local recurrence rates due mainly to undetected LN metastasis. Ideally, minimized FNR for detecting LN metastasis would maximize the identification of patients suitable for local excision.

A total of 246 patients with clinical T1/T2 rectal cancer who underwent MRI within one month before surgery were included in this study. The tumor location, morphology, tumor diameter/volume, and depth of tumor invasion were evaluated using MRI. Patients were categorized into three groups according to the LN size and morphology: Group 1, no discernible regional LN or all visible LNs <3 mm; Group 2, not belonging to either Group 1 or 3; and Group 3, at least one LN >5 mm or showing irregular margins or internal heterogeneity.

Lower LN group and partial tumor invasion of the muscular layer were significantly associated with lower risks of LN metastasis. When it was considered negative for LN metastasis if the patient belonged to LN Group 1 or 2 regardless of the depth of tumor invasion, the FNR were 13.6%. When only LN Group 1 was considered negative for LN metastasis, the FNR was still 9.7%. Addition of invasion depth to the diagnostic criteria decreased the FNR from 13.6% to 5.8% (LN Group 1/2 with partial tumor invasion) and from 9.7% to 3.2% (LN Group 1 with partial tumor invasion).

Inclusion of tumor invasion depth in LN evaluation using preoperative MRI can reduce the FNR for LN metastasis in patients with clinical T1 or T2 rectal cancer.

We can better identify a low risk group for regional LN metastasis among patients with early-stage rectal cancer by assessing the depth of tumor invasion and regional LNs using preoperative MRI. Application of these criteria may help minimize the likelihood of offering local excision to a patient who might have LN metastasis.

Sohn, B, An, C, Lim, J, Kim, M, Patient Selection for Local Excision: Preoperative MRI to Predict Negative Lymph Node Metastasis in Patients with Clinical T1 and T2 Stage Rectal Cancer.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14007143.html