Human Epidermal Growth Factor Receptor 2 (HER-2) Status in Gastric and Gastro-Esophageal Junction (GEJ) Carcinoma

Positive HER-2 status was defined as either immunohistochemistry (IHC) score of 3+ or IHC score 2+/in situ hybridization (ISH) score +, as per the trastuzumab Summary of Product Characteristics (SPC). The HER-2 status in tumor specimens was determined using the pathologist's choice of IHC and ISH techniques in local laboratories, and using IHC 4B5 and silver ISH (SISH) in centralized laboratories. The kappa coefficient was used to evaluate the true concordance between the HER-2 status determined by local and centralized laboratories. The kappa coefficient value was interpreted according to the Landis and Koch classification as follows: a) less than (<) 0: less than chance agreement, b) 0.01-0.20: slight agreement, c) 0.21-0.40: fair agreement, d) 0.41-0.60: moderate agreement, e) 0.61-0.80: substantial agreement, and f) 0.81-0.99: almost perfect agreement.

The Lauren classification is based on examination of histologic specimens under the microscope and divides adenocarcinoma of the stomach into 3 types: 1) Diffuse type: tumor cells are poorly differentiated, behave aggressively and tend to scatter throughout the stomach (rather than form glands). This type metastasizes to other parts of the body much quicker than intestinal type tumors, 2) Intestinal type: tumor cells are well differentiated, grow slowly and tend to form glands, 3) Mixed type: this type is made up of both intestinal and diffuse types.

The TNM stage system includes information about the size of the primary tumor (T), whether the cancer has spread to nearby lymph nodes (N) and whether the cancer has metastasized to other parts of the body (M). In the T classification TX indicates that the main tumor cannot be measured, T1, T2, T3 and T4 refer to the size and/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into nearby tissues. In the N classification NX indicates that the cancer in nearby lymph nodes cannot be measured, N0 indicates that there is no cancer in nearby lymph nodes, N1, N2 and N3 refer to the number and location of lymph nodes that contain cancer. The higher the number after the N, the more lymph nodes that contain cancer. In the M classification MX indicates that the metastasis cannot be measured, M0 indicates that the cancer has not spread to other parts of the body and M1 indicates that the cancer has spread to other parts of the body.

Positive HER-2 status was defined as either immunohistochemistry (IHC) score of 3+ or IHC score 2+/in situ hybridization (ISH) score +, as per the trastuzumab Summary of Product Characteristics (SPC). The HER-2 status in tumor specimens was determined using IHC 4B5 and silver ISH (SISH) in centralized laboratories. The weighted kappa coefficient was used to evaluate the true concordance between the HER-2 status determined by IHC 4B5 and SISH. The weighted kappa coefficient value was interpreted according to the Landis and Koch classification as follows: a) less than (<) 0: less than chance agreement, b) 0.01-0.20: slight agreement, c) 0.21-0.40: fair agreement, d) 0.41-0.60: moderate agreement, e) 0.61-0.80: substantial agreement, and f) 0.81-0.99: almost perfect agreement.