Stereotactic surgery.

Mutations of an oncogene, K-ras, are associated with the development and progression of many types of human cancer. To elucidate the significance of K-ras mutations in gastric carcinogenesis, we examined K-ras mutations in gastric cancers and in Helicobacter pylori-associated chronic gastritis (H. pylori-CG), which is associated with an increased risk for the gastric cancer development. Specimens of gastric cancer and H. pylori-CG were obtained from 64 gastric cancer patients with H. pylori-CG, 99 cancer-free H. pylori-CG patients and 30 H. pylori-negative healthy subjects. K-ras mutations were examined by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), followed by DNA sequencing analysis. K-ras mutations were detected in 4 of 48 (8.3%) gastric cancers, in 10 of 163 (6.1%) H. pylori-CG and none of the 30 H. pylori-negative healthy subjects. In the gastric cancer patients, mutated K-ras was detected in differentiated type cancers but not in any of the undifferentiated type cancers. K-ras mutations in H. pylori-CG were significantly more frequent in gastric cancer patients than in cancer-free patients (10.9% vs. 3.0%, p = 0.044). In addition, K-ras mutations in H. pylori-CG were significantly more frequent in patients with K-ras mutated gastric cancer than in patients with K-ras unmutated gastric cancer (50.0% vs. 3.7%, p = 0.037). These data suggest that the genetic mechanism(s) of carcinogenesis differs between the differentiated type and the undifferentiated type of gastric cancer and that K-ras mutations may be involved in the early stages of gastric carcinogenesis of the differentiated type.

Biopsy↗

PubMed2002

Tests for equivalence or non-inferiority for paired binary data.

Assessment of therapeutic equivalence or non-inferiority between two medical diagnostic procedures often involves comparisons of the response rates between paired binary endpoints. The commonly used and accepted approach to assessing equivalence is by comparing the asymptotic confidence interval on the difference of two response rates with some clinical meaningful equivalence limits. This paper investigates two asymptotic test statistics, a Wald-type (sample-based) test statistic and a restricted maximum likelihood estimation (RMLE-based) test statistic, to assess equivalence or non-inferiority based on paired binary endpoints. The sample size and power functions of the two tests are derived. The actual type I error and power of the two tests are computed by enumerating the exact probabilities in the rejection region. The results show that the RMLE-based test controls type I error better than the sample-based test. To establish an equivalence between two treatments with a symmetric equivalence limit of 0.15, a minimal sample size of 120 is needed. The RMLE-based test without the continuity correction performs well at the boundary point 0. A numerical example illustrates the proposed procedures.

Biopsy↗