4539 Is high-frequency ultrasound probe a useful modality for invasion depth diagnosis of early gastric cancers?

Abstract

Background: Precise preoperative invasion depth staging is essential to determine a therapeutic strategy for early gastric cancer, because endoscopic mucosal resection (EMR) is satisfactory for intramucosal cancers (m-ca) but gastrectomy is necessary for submucosal cancers (sm-ca). Recently, high-frequency ultrasound probe (HFUP) has become available and it enabled to provide high resolutional images especially for small and superficial gastric cancers. Aims: To clarify whether or not HFUP is useful for invasion depth diagnosis, we prospectively compared its accuracy with endoscopy. Patients and Methods: We prospectively studied 113 consecutive patients with 114 early gastric cancers (T1 stage), consisting of 81 mca and 33 sm-ca, that were subsequently treated by EMR (n=59) or gastrectomy (n=55) between Mar. 1995 and Sep. 1999. The criteria of invasion depth diagnosis were referred to the report for endoscopy (Sano T, et al. Dig Dis Sci 35, 1990) and for HFUP (Yasuda K, et al. Stomach and Intestine 27, 1992). The invasion depth was diagnosed prospectively based on these criteria. HFUP was performed by using 15 or 20 MHz probes. The macroscopic type was divided into Type I (protruded, n=4) and Type II (superficial, n=110). Type II was subdivided into following 3 types; superficial elevated (IIa, n=35), superficial depressed with ulceration (IIc Ul(+), n=26), superficial depressed without ulceration (IIcUl(-), n=42) and flat elevated with depression (IIa+IIc, n=7). Results: No significant difference was found in the overall accuracy between the two modalities, that were 77.8% in endoscopy and 73.7% in HFUP. However, HFUP could provide correct diagnosis in 9 (34.6%) of 26 cases misdiagnosed by endoscopy. Conversely, endoscopy did so in 10 (37.0%) of 27 cases incorrectly diagnosed by HFUP. Both modalities showed a significantly lower accuracy rate in type IIc Ul(+) than in the other macroscopic types (p<0.01, respectively). Misdiagnosis by HFUP found in 27 lesions were due to submucosal fibrosis in 15, ultrasound attenuation in 5, microscopic invasion to the submucosal layer in 3 and technical difficulties in 4. Conclusions: There is no difference in the accuracy of invasion depth diagnosis of early gastric cancer between endoscopy and HFUP, although HFUP is a useful procedure for preoperative staging in colorectal cancers. This difference is considered to be due to the difficulty for HFUP to discriminate submucosal cancer invasion from fibrosis that is often found in gastric cancers.