Are rigid probes sufficient to provide reliable data for rectal cancer staging?

Dear Editor,

We read with interest the article entitled “Rectal cancer staging: Correlation between the evaluation with radial echoendoscope and rigid linear probe” by Colaiacovo et al.[1] In 48 preoperative patients with rectal carcinoma, the authors scrutinized if there was a good correlation between T and N staging with radial endoscopic ultrasound (EUS) (i.e., performed with a flexible echoendoscope) versus linear endorectal ultrasound performed with a rigid probe. They found a perfect agreement between the two techniques with regard to T staging and a moderate agreement with regard to N staging. Based on their findings, the authors underlined the equivalence in rectal cancer staging accuracy between flexible radial EUS and rigid linear endorectal ultrasound.

However, we believe that this assumption cannot be completely endorsed due to several reasons. First, to achieve complete staging of rectal cancer, luminal intubation with EUS scope up to 20-25 cm from the anus is needed to investigate the presence of malignant iliac lymph nodes that are designated as M1 stage.[23] This alters patient management with regard to surgical fitness, extent of resection, and/or radiation field. On the other hand, we cannot get any information about iliac lymph nodes with a rigid probe that is designed only for blind rectal examination. Second, a flexible echoendoscope shows the advantage of tumor visualization and traversing stenotic tumors. In this situation, the reliability of data obtained with rigid probes with regard to T and N staging is also questionable. Furthermore, a proximally localized rectal cancer may not be adequately evaluated by rigid probes. In the present study, the authors did not provide any data about the effects of tumor localization and the degree of luminal stenosis induced by the tumor itself on T and N staging with rigid probes.

With the growing acceptance of neoadjuvant treatment for T3, T4, N+ rectal cancer, and sphincter-saving transanal excision for early lesions (T1N0), we believe that flexible echoendoscopes can provide the most reliable data for the locoregional staging of rectal cancer. Adequate training and experience are clearly needed to obtain the highest degree of accuracy.

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