Gastric cancer: an update

Utilidad de la laparoscopia de estadificación frente a la tomografía axial computarizada para detectar metástasis peritoneales en el adenocarcinoma gástrico avanzado

  Introducción. El adenocarcinoma gástrico es una de las neoplasias más frecuentes. La tomografía computarizada abdominal con contraste es el método estándar para la estadificación; tiene una sensibilidad del 30 al 73 % y una especificidad del 83 al 100 %. La laparoscopia detecta hasta el 30 % de los casos de enfermedad metastásica que no se haya observado en los estudios de imágenes. En la Clínica Universitaria Colombia se realiza estadificación rutinaria con tomografía y laparoscopia más lavado peritoneal. Objetivos. Determinar la utilidad de la laparoscopia para detectar la carcinomatosis peritoneal en los pacientes con adenocarcinoma gástrico avanzado en un centro de referencia. Materiales y métodos. Se llevó a cabo un estudio descriptivo y retrospectivo, en el cual se analizaron todas las historias clínicas de los pacientes con cáncer gástrico atendidos en la Clínica Universitaria Colombia entre el 2013 y el 2016. Se confrontó el hallazgo de la laparoscopia con el de la tomografía abdominal, buscando falsos negativos para la enfermedad peritoneal. Resultados. Se incluyeron 94 pacientes con adenocarcinoma gástrico. La localización en el cuerpo gástrico fue la más frecuente (47,9 %). La tomografía reportó estadio T3 en el 56,4 %, N0 en el 55,3 % y M0 en el 97,9 % de los casos. La laparoscopia reportó estadio T3 en el 43,6 %, ganglios comprometidos en el 56,4 % y carcinomatosis peritoneal (M1) en el 11,7 %. Discusión. Un radiólogo experimentado detecta una gran proporción de las enfermedades peritoneales, pero la laparoscopia detecta hasta 11 % de aquellas que no son evidentes en los exámenes de imágenes. El lavado peritoneal no prolonga el tiempo quirúrgico ni incrementa la morbilidad, lo cual favorece su realización rutinaria. Se puede recomendar la laparoscopia en aquellos pacientes con resultados tomográficos negativos, evitando la cirugía cuando la neoplasia es irresecable. La laparoscopia tiene un impacto positivo en el manejo integral del cáncer gástrico, acorde con la literatura mundial.

Could quantitative real-time polymerase chain reaction assay serve as an alternative test method to evaluate human epidermal growth factor receptor 2 status of gastric carcinoma in the South Asian setting?

BACKGROUND

Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification are/is linked to a dismal outcome of gastric carcinoma (GCa). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are key methods to identify patients for HER2 targeted therapy. Drawbacks of both the methods warrant novel tests. Hence, we evaluated the value of quantitative real-time polymerase chain reaction (qPCR) as an alternative test method, relative to IHC to detect HER2 status of GCa and to find relationship between these  results with demographic/clinicopathological data.

METHOD

Twenty GCa patients with known IHC HER2 scores were evaluated. qPCR was performed for the HER2 gene and amyloid precursor protein (reference gene) in formalin-fixed paraffin-embedded GCa tissue. Cycle threshold values (Ct) were analyzed using the Pfaffl method to detect HER2 gene amplification.

RESULTS

HER2 positivity rates by IHC and qPCR were 20% and 35%, respectively. The sensitivity and specificity of qPCR were 67% and 76%, respectively, relative to IHC. qPCR results were reproducible. The diagnostic consistency between IHC and qPCR (κ = 0.146) was slightly agreeable (0.01 < k < 0.20), with a 65% concordance. Based on McNemar's test, there was no significant difference between the results of the two tests. IHC HER2 protein expression had relationship with the tumor (TNM) stage and Lauren histological type (p < 0.05). Positive HER2 gene expression by qPCR showed relationship with depth of invasion, lymph node involvement, and degree of differentiation (p < 0.05).

CONCLUSION

Cost-effective qPCR could serve as an alternative test method for detection of HER2 status of GCa. Both HER2 overexpression by IHC and gene amplification by qPCR are associated with adverse clinicopathological features.

Gene Expression Profiling of Gastric Cancer

Gastric cancer is the second leading cause of cancer death worldwide, both in men and women. A genomewide gene expression analysis was carried out to identify differentially expressed genes in gastric adenocarcinoma tissues as compared to adjacent normal tissues. We used Agilent's whole human genome oligonucleotide microarray platform representing ~41,000 genes to carry out gene expression analysis. Two-color microarray analysis was employed to directly compare the expression of genes between tumor and normal tissues. Through this approach, we identified several previously known candidate genes along with a number of novel candidate genes in gastric cancer. Testican-1 (SPOCK1) was one of the novel molecules that was 10-fold upregulated in tumors. Using tissue microarrays, we validated the expression of testican-1 by immunohistochemical staining. It was overexpressed in 56% (160/282) of the cases tested. Pathway analysis led to the identification of several networks in which SPOCK1 was among the topmost networks of interacting genes. By gene enrichment analysis, we identified several genes involved in cell adhesion and cell proliferation to be significantly upregulated while those corresponding to metabolic pathways were significantly downregulated. The differentially expressed genes identified in this study are candidate biomarkers for gastric adenoacarcinoma.

Prognostic significance of p53 protein expression in early gastric cancer

Mutations of the p53 tumor suppressor gene have been associated with abnormalities in cell cycle regulation, DNA repair and synthesis, apoptosis, and it has been implicated in the prognosis of advanced gastric cancer. The aim of this study was to evaluate the occurrence of p53 gene mutation and its possible prognostic implications in early gastric cancer. In a retrospective study, we studied 80 patients with early gastric cancer treated surgically between 1982 and 2001. Mutation of p53 gene was investigated in surgical gastric specimens by immunohistochemistry, and results were analyzed in relation to gender, age, macroscopic appearance, size and location of tumor, presence of lymph nodes, Lauren's histological type, degree of differentiation, and the 5-year survival. The expression of p53 was more frequent among the intestinal type (p = 0.003), the differentiated (p = 0.007), and the macroscopically elevated tumors (p = 0.038). Nevertheless, the isolated expression of p53 was not associated with the 5-year survival, or with the frequency of lymph node involvement. The degree of differentiation was detected as an independent factor related to the outcome of patients (0.044). Significantly shorter survival time was found in p53-negative compared with p53-positive patients, when considering the degree of differentiation of tumors, as assessed by Cox regression analysis (0.049). The association of p53 with the intestinal type, the degree of differentiation and morphological characteristics, may reflect the involvement of chronic inflammatory process underlying early gastric cancer. In this population sample, the expression of p53 alone has no prognostic value for early gastric cancer. However, the significant difference in p53 expression between subgroups of degree of differentiation of tumors can influence post-operative outcome of patients and may be related to possible distinct etiopathogenic subtypes.

The distinctive gastric fluid proteome in gastric cancer reveals a multi-biomarker diagnostic profile

BACKGROUND

Overall gastric cancer survival remains poor mainly because there are no reliable methods for identifying highly curable early stage disease. Multi-protein profiling of gastric fluids, obtained from the anatomic site of pathology, could reveal diagnostic proteomic fingerprints.

METHODS

Protein profiles were generated from gastric fluid samples of 19 gastric cancer and 36 benign gastritides patients undergoing elective, clinically-indicated gastroscopy using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry on multiple ProteinChip arrays. Proteomic features were compared by significance analysis of microarray algorithm and two-way hierarchical clustering. A second blinded sample set (24 gastric cancers and 29 clinically benign gastritides) was used for validation.

RESULTS

By significance analysyis of microarray, 60 proteomic features were up-regulated and 46 were down-regulated in gastric cancer samples (p < 0.01). Multimarker clustering showed two distinctive proteomic profiles independent of age and ethnicity. Eighteen of 19 cancer samples clustered together (sensitivity 95%) while 27/36 of non-cancer samples clustered in a second group. Nine non-cancer samples that clustered with cancer samples included 5 pre-malignant lesions (1 adenomatous polyp and 4 intestinal metaplasia). Validation using a second sample set showed the sensitivity and specificity to be 88% and 93%, respectively. Positive predictive value of the combined data was 0.80. Selected peptide sequencing identified pepsinogen C and pepsin A activation peptide as significantly down-regulated and alpha-defensin as significantly up-regulated.

CONCLUSION

This simple and reproducible multimarker proteomic assay could supplement clinical gastroscopic evaluation of symptomatic patients to enhance diagnostic accuracy for gastric cancer and pre-malignant lesions.