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Cáncer Gástrico: Definición y Epidemiología

Introducción al Cáncer Gástrico

• La clase inicia con una introducción sobre el cáncer gástrico, destacando su relevancia en la salud pública.

• El cáncer gástrico es una neoplasia frecuente del tracto gastrointestinal, siendo la quinta causa de incidencia y la tercera en mortalidad por cáncer según la OMS en 2018.

Tendencias y Estadísticas

• Aunque la incidencia general ha disminuido, se observa un aumento en el tipo difuso de cáncer gástrico, que es más agresivo y afecta a personas jóvenes menores de 40 años.

• La epidemiología muestra que es más común en varones (2:1), con una edad media de diagnóstico alrededor de los 60 años.

Distribución Geográfica

• En Asia oriental (China, Japón) y algunos países latinoamericanos (Guatemala, Costa Rica, Ecuador, Perú y Chile), se reportan las tasas más altas de cáncer gástrico.

• Las tasas son significativamente más bajas en Norteamérica, África del Norte, sur de Asia y Australia.

Detección Temprana y Supervivencia

Desafíos en Detección

• A pesar del avance en métodos diagnósticos, menos del 30% de los casos se detectan en etapas tempranas a nivel mundial.

Tasa de Supervivencia

• La tasa de supervivencia a cinco años está directamente relacionada con el estadio al momento del diagnóstico; más del 90% para casos tempranos localizados solo en mucosa.

• Para casos avanzados, la supervivencia puede caer entre el 10% y el 25%.

Incidencia Regional y Mortalidad

Datos Específicos para Perú

• En Perú hay aproximadamente 6300 nuevos casos anuales; el estómago es uno de los tipos más comunes tanto para hombres como mujeres.

Variaciones por Departamento

• Junín, Huánuco, Huancavelica, La Libertad y Lima presentan mayores tasas de mortalidad debido a factores como acceso limitado a servicios médicos.

Factores de Riesgo Asociados

Clasificación de Factores

• Se identifican factores definitivos (como Helicobacter pylori), probables y cuestionables que aumentan el riesgo de desarrollar cáncer gástrico.

Lesiones Premalignas

• Lesiones como displasia e gastritis atrófica son consideradas premalignas; su presencia requiere seguimiento regular debido al incremento del riesgo asociado.

Pólipos Gástricos

• Los pólipos adenomatosos también son un factor relevante aunque menos frecuentes comparados con aquellos encontrados en colon.

Understanding Gastric Cancer Risk Factors

Histological Characteristics of Polyps

• The decision to remove gastric polyps depends on their histological characteristics; some may not require removal if they do not raise suspicion for malignancy.

Surgical History and Genetic Factors

• Previous gastric surgeries, especially those related to a history of gastric cancer, increase the risk of developing gastric cancer.

• Genetic predispositions such as familial gastric cancer and hereditary syndromes like Peutz-Jeghers syndrome are significant risk factors.

Peutz-Jeghers Syndrome Insights

• This syndrome is characterized by polyp formation in the digestive tract and an increased incidence of various cancers, including ovarian and breast cancers.

Chronic Conditions and Lifestyle Influences

• Chronic irritation from reflux can lead to mucosal inflammation, increasing cancer risk.

• High salt intake has been linked to mucosal damage and higher infection rates with Helicobacter pylori (HP), which can elevate cancer risk.

Obesity and Other Contributing Factors

• Obesity is associated with increased risks due to its relation to gastroesophageal reflux disease (GERD).

• Conditions like pernicious anemia, which affects vitamin B12 absorption, are also linked to higher gastric cancer risks.

Protective Factors Against Gastric Cancer

Dietary Considerations

• Regular consumption of fruits, vegetables, and vitamin C may offer protective benefits against gastric cancer.

Controversial Protective Elements

• The role of hyperplastic polyps in diet-related protection remains unclear; high nitrate diets or green tea consumption have not been conclusively proven as protective.

Gastric Cancer Pathophysiology

Carcinogenesis Cascade Overview

• The progression from chronic gastritis to gastric cancer involves several stages: atrophy, metaplasia, dysplasia leading ultimately to malignancy.

Molecular Alterations in Cancer Development

• Infections like HP can trigger autoimmune responses that alter acid secretion and promote bacterial overgrowth—factors contributing to carcinogenesis.

Genetic Mutations Impacting Cancer Risk

• Mutations in genes such as P53 disrupt DNA repair mechanisms leading to abnormal cell proliferation; alterations in CDH1 are particularly associated with diffuse gastric cancer.

Understanding Gastric Cancer Progression

Pathway from Normal Stomach to Cancer

• The progression from a normal stomach to gastric cancer can be initiated by exposure to pathogens like Helicobacter pylori (HP), leading to chronic conditions such as gastritis.

• Chronic gastritis can evolve into atrophic gastritis, which may further progress to intestinal metaplasia, characterized by the transformation of gastric epithelium into intestinal-type cells with goblet cells.

• Atrophic gastritis results in glandular loss and decreased acid secretion, increasing susceptibility to HP infections and potentially leading to dysplasia and adenocarcinoma over several years.

• Premalignant lesions such as metaplasia and dysplasia indicate a higher risk for cancer progression, necessitating treatment interventions for patients with these conditions.

Characteristics of Helicobacter Pylori

• HP is a gram-negative spiral bacterium that induces persistent inflammatory reactions in the gastric mucosa, altering mucus layers and causing chronic inflammation.

• Endoscopic findings may reveal nodular patterns indicative of HP infection; however, not all infected individuals will exhibit these characteristics.

Endoscopic Findings and Histological Correlation

• Endoscopic images can show vascular patterns indicating gastric atrophy; histological confirmation is essential for accurate diagnosis.

• Metaplastic changes may present as white nodules during endoscopy, requiring histological validation for proper assessment.

Classification Systems for Gastritis

• The Sydney classification system guides biopsy sampling locations in the stomach to differentiate between atrophic and non-atrophic gastritis effectively.

• The Olga system evaluates the extent of atrophy based on biopsy results, influencing surveillance strategies according to cancer risk levels.

Surveillance Recommendations

• Regular biopsies are recommended for monitoring patients with varying degrees of atrophy; those classified under higher risk categories require more frequent follow-ups due to significantly increased cancer risks.

Rare Forms of Gastric Cancer

• Hereditary diffuse gastric cancer is rare but aggressive, often presenting with thickened stomach walls that complicate biopsy procedures.

• This type of cancer is associated with CDH1 gene mutations and typically affects younger individuals under 40 years old.

Cáncer Gástrico: Diagnóstico y Clasificación

Criterios de Diagnóstico Hereditario

• La asociación del cáncer gástrico con otros tipos de cáncer, como el cáncer de mama, sugiere la posibilidad de un componente hereditario en pacientes jóvenes.

• Se deben considerar criterios diagnósticos específicos, como tener dos o más familiares de primer grado con cáncer gástrico difuso antes de los 50 años.

• Antecedentes personales o familiares de cáncer gástrico y mamario pueden indicar un tipo hereditario del cáncer gástrico.

Importancia del Seguimiento Genético

• Es crucial realizar estudios genéticos y endoscopias de seguimiento para pacientes diagnosticados con este tipo de cáncer.

• La falta de seguimiento adecuado puede llevar a que los pacientes sean diagnosticados en etapas avanzadas, reduciendo significativamente su esperanza de vida.

Clasificaciones Histológicas del Cáncer Gástrico

Tipos Intestinal y Difuso

• El cáncer gástrico se clasifica en dos tipos principales: intestinal (más frecuente) y difuso (menos frecuente pero en aumento).

• Según la OMS, el tipo intestinal incluye subtipos como tubulares, papilar y mucinoso; mientras que el difuso es más agresivo y pobremente diferenciado.

Características del Cáncer Intestinal vs. Difuso

• El patrón intestinal afecta principalmente a hombres mayores de 50 años, siendo más prevalente en regiones como China, Corea y Japón. Crece exofíticamente formando úlceras.

• El tipo difuso afecta por igual a hombres y mujeres jóvenes (menores de 40 años), tiene una presentación infiltrativa y está relacionado con factores hereditarios. Su incidencia está aumentando globalmente.

Clasificación según Etapas del Cáncer

Cáncer Temprano vs Avanzado

• El cáncer gástrico temprano se limita a la mucosa sin afectar capas más profundas; mientras que el avanzado penetra hasta la serosa o más allá.

• Existen diferentes subtipos dentro del cáncer temprano basados en características morfológicas: protruidos, superficiales elevados, planos, deprimidos y excavados (úlcera).

Técnicas Endoscópicas para Detección

Uso de Cromendoscopía

• La cromendoscopía electrónica ayuda a identificar lesiones precoces al realzar bordes e identificar mejor las características morfológicas durante la endoscopia.

• Las tinciones específicas permiten visualizar mejor las lesiones pequeñas que podrían ser indicativas de malignidad antes que crezcan significativamente o se conviertan en casos avanzados.

Understanding Gastric Lesions and Their Implications

Characteristics of Ulcers

• The presence of elevated lesions can indicate potential malignancy, especially when there is an "amputation" of folds observed in the tissue.

• A comparison between benign and malignant ulcers shows that benign ones typically have regular borders without retraction, while malignant ones may exhibit deep lesions causing mucosal retraction.

Biopsy Techniques

• It is crucial to take biopsies from both the edges of the ulcer and the surrounding antral area to check for Helicobacter pylori (HP), which is associated with peptic ulcer disease.

Identifying Vascular Patterns

• Utilizing specific staining techniques like FE (Fuji) helps visualize vascular patterns in lesions, aiding in distinguishing between adenomas and potentially neoplastic changes.

• Irregular glandular patterns with dilated vessels suggest a higher likelihood of malignancy compared to orderly arrangements seen in benign conditions.

Classification of Gastric Cancer

• Advanced gastric cancer is classified using Borman's system from 1 to 5, where Borman 1 indicates well-defined polypoid growth, while Borman 4 represents diffuse infiltration leading to rigidity in the gastric wall.

Clinical Presentation and Diagnosis

• Early-stage gastric cancers are often asymptomatic (80%), discovered incidentally during screenings; however, advanced stages present classic symptoms such as weight loss and abdominal pain.

• Symptoms like early satiety, nausea, vomiting, melena, or ascites may occur if the cancer infiltrates distal stomach areas.

Physical Examination Findings

• In advanced cases, physical exams may reveal palpable masses or hepatomegaly due to metastasis. Specific signs include Virchow's node (supraclavicular lymphadenopathy), Sister Mary Joseph nodule (umbilical metastasis), and Krukenberg tumor (ovarian involvement).

Laboratory Investigations

• Blood tests may show anemia related to occult blood loss. Liver function tests can indicate hepatic infiltration due to metastatic disease.

Advances in Endoscopic Diagnosis and Staging of Gastric Cancer

Historical Context and Diagnostic Techniques

• The use of radiological diagnostics has diminished, with endoscopy becoming the primary method for screening gastric cancer.

• A double contrast technique was previously employed, using a probe to introduce both contrast and air for enhanced imaging; however, it is now rarely used.

• Endoscopic diagnosis is considered the most reliable and well-tolerated method, with low mortality rates associated with biopsies.

Challenges in Early Detection

• Early lesions are more challenging to diagnose compared to advanced ones; large lesions can sometimes be misidentified.

• Techniques like chromoendoscopy are utilized primarily for early lesion identification rather than larger tumors.

Staging Methods

• Staging typically involves tomography; endoscopic ultrasound (EUS) may be used for small lesions to assess depth of invasion.

• Blood tests are conducted to evaluate anemia and liver function, while diagnostic laparoscopy may be necessary in certain cases.

Understanding Tumor Depth and Classification

• The TNM classification system is crucial for determining tumor depth: T1 indicates early-stage cancer confined to mucosa, while T2 or higher signifies advanced disease.

• EUS helps assess whether an endoscopic resection is feasible based on lesion depth.

Patterns of Tumor Dissemination

• Lymphatic spread is common in advanced gastric cancers, often affecting nearby structures such as the lesser curvature or adjacent organs.

• Direct invasion into surrounding tissues occurs frequently, particularly with tumors located at specific anatomical sites like the pylorus or greater curvature.

Peritoneal Carcinomatosis Indicators

• Signs of peritoneal carcinomatosis include ascites and peritoneal nodules; once present, the disease becomes incurable.

• Recurrence post-curative surgery often manifests as peritoneal dissemination.

Treatment Considerations Based on Stage

• Treatment strategies depend on staging; early-stage cancers (T1 or less) may allow for endoscopic resection if adequately assessed through prior studies.

Cancer Treatment Approaches

Overview of Treatment Options

• Discussion on treatment strategies for T2 and beyond, including preoperative chemotherapy, surgery, and postoperative adjuvant therapy.

• In cases of inoperable patients or those with metastasis, the focus shifts to palliative care, pain management, and supportive chemotherapy.

Surgical Interventions

• Surgical options range from subtotal gastrectomy to total gastrectomy depending on tumor location; distal tumors may allow for subtotal procedures if no organ invasion is present.

• Total gastrectomy involves complete removal of the stomach along with lymph nodes; an esophagojejunostomy is performed to connect the esophagus to the intestine.

Post-Surgical Considerations

• Patients post-surgery may experience complications such as dumping syndrome due to altered anatomy affecting nutrient absorption.

• Emphasis on careful evaluation of surgical techniques based on tumor location and potential complications.

Endoscopic Treatments for Early Cancers

Indications for Endoscopic Procedures

• Endoscopic treatments are reserved for early-stage cancers like well-differentiated adenocarcinomas under 2 cm without vascular involvement.

• Two main techniques discussed: endoscopic mucosal resection (EMR) and submucosal dissection (ESD), each with distinct risks and benefits.

Technique Comparisons

• ESD allows deeper resection but carries higher risks of perforation; EMR is quicker but less comprehensive.

• Both procedures aim for complete resection while minimizing recurrence risk; choice depends on lesion size and endoscopist expertise.

Preventive Measures Against Advanced Cancer

Importance of Prevention

• Stressing the need for preventive measures starting from age 40–45 through regular screenings and awareness of family history.

• Recommendations include lifestyle changes, nutritional improvements, and eradication of Helicobacter pylori (HP).

Goals in Cancer Prevention

• The ultimate goal is to prevent advanced cancer stages that limit curative treatment options; emphasis on proactive health measures.