PERITUMORAL TISSUE REACTION AT TRANSRECTAL US AS A POSSIBLE CAUSE OF OVERSTAGING IN RECTAL-CANCER - HISTOPATHOLOGIC CORRELATION

PURPOSE: To assess if peritumoral tissue reaction (PTR) can be differe ntiated from tumor with transrectal ultrasound (TRUS) to avert oversta ging. MATERIALS AND METHODS: Preoperative TRUS results in 40 consecuti ve patients with biopsy-proved rectal cancer were compared with histop athologic reports on the specimens (study 1). To lest the hypothesis t hat areas more anechoic than the tumor were deemed responsible for inc orrect staging in study 1, a prospective study was undertaken in anoth er 40 consecutive patients (study 2). The thickest part of PTR was mea sured, and results were compared with the histopathologic findings. RE SULTS: In study 1, 28 (70%) of 40 rectal cancers were staged correctly with TRUS. PTR was responsible for the misinterpretation in six of se ven overstaged cases. In study 2, 38 (95%) of 40 cancers were staged c orrectly, and the presence or absence of PTR was described in 39 cases (98%). A statistically significant positive correlation was noted bet ween histopathologic classification of PTR and its thickness measured with TRUS (P = .0001). CONCLUSION: Because of its more anechoic appear ance, PTR may be differentiated from the tumor by means of TRUS. This may lead to a statistically significantly higher accuracy of TRUS in t he staging of rectal cancer due to the avoidance of overstaging.