Intestinal Cancer: Types, Symptoms, Causes, Diagnosis & Treatment

Intestinal cancer refers to malignancies that develop in the small or large intestine, impacting digestion and nutrient absorption. Although it is less common than other gastrointestinal cancers, it can be life-threatening if not diagnosed and treated early. The cancer may originate in the intestines or spread from other organs. Understanding intestinal cancer's types, symptoms, causes, diagnostic methods, and treatment options is crucial for timely intervention and improved prognosis, as its incidence worldwide is increasing.

Types of Intestinal Cancer

Intestinal cancers are classified primarily based on their location and the cellular origin of cancerous tumor. some of the prominent types of intestinal cancer include:

Small Intestinal Cancer

This type is relatively rare and affects the small intestine, which includes the duodenum, jejunum, and ileum. The small bowel/ small intestine plays a key role in nutrient absorption, and tumors in this region can lead to severe malnutrition and obstruction. Common subtypes include:

• Adenocarcinoma: Arises from glandular cells, mostly in the duodenum, often associated with inflammatory conditions such as Crohn's disease.
• Neuroendocrine Tumors (Carcinoid Tumors): Slow-growing tumors that often occur in the ileum and secrete hormones that cause systemic symptoms.
• Lymphoma: Affects lymphoid tissue within the intestine, commonly associated with immunosuppressive conditions or infections such as the Epstein-Barr virus.
• Sarcoma (Gastrointestinal Stromal Tumors - GISTs) : Originates in the connective tissue of the intestinal wall and often presents as an abdominal mass with bleeding.

Colorectal Cancer (Large Intestinal Cancer)

This includes malignancies affecting the colon and rectum. Globally, colorectal cancer is one of the most common types of cancer and is influenced by genetic and environmental factors. Common types include:

• Adenocarcinoma: Accounts for over 90% of colorectal cancers and typically develops from pre-existing polyps.
• Lymphoma: Affects lymphoid tissue within the colon, which can lead to severe immune dysfunction.
• Gastrointestinal Stromal Tumors (GISTs): Similar to small intestinal sarcomas and can arise in any part of the digestive tract.
• Neuroendocrine Tumors: Less common but can develop in the colon and rectum, often diagnosed incidentally.

Intestinal Cancer Symptoms

Intestinal cancer, which includes malignancies of the small and large intestines, often presents with subtle or nonspecific symptoms in the early stages, making early detection challenging. The symptoms largely depend on the tumor's location, size, and rate of progression.

Small intestine cancer symptoms 

Small intestinal cancer often carries mild symptoms, that are majorly asymptomatic and shows the below symptoms:

• Mild, intermittent abdominal discomfort: Patients may experience vague pain or cramping that is often dismissed as indigestion or gas.
• Changes in bowel habits: This may include occasional constipation, diarrhea, or unexplained fluctuations in stool consistency.
• Mild fatigue and weakness: Chronic low-grade anemia may develop due to occult (hidden) blood loss in stools, leading to early fatigue.

Large intestine cancer symptoms 

Large intestinal cancer mostly shows progressive symptoms, that mainly indicate the growth of the tumor and surrounding structure involvement. Some of the large intestinal cancer progressive symptoms are mentioned below:

• Abdominal Pain and Discomfort
• Persistent pain that may be dull, cramping, or colicky.
• Pain intensity may increase over time as the tumor enlarges or causes obstruction.
• Tumors in the small intestine may cause episodic pain that worsens after meals due to partial obstruction.

• Bowel Habit Alterations
• Constipation or Diarrhea: Irregular bowel movements may indicate tumor-related obstruction or irritation.
• Narrowing of stools (pencil-thin stools): Often a sign of a growing tumor in the large intestine causing luminal narrowing.
• Incomplete evacuation: Patients may feel the urge to defecate but pass little stool, which may be associated with rectal or sigmoid colon involvement.

• Rectal Bleeding and Blood in Stool
• Hematochezia (bright red blood in stool): Suggests lower gastrointestinal bleeding, often associated with colorectal tumors.
• Melena (dark, tarry stools): Occurs when bleeding originates higher in the gastrointestinal tract, such as in the small intestine. Chronic blood loss can lead to iron-deficiency anemia, resulting in pallor, fatigue, and dizziness.

• Unexplained Weight Loss
• Cancer-induced hypermetabolism and systemic inflammatory responses contribute to weight loss, however, reduced nutrient absorption, especially in small intestinal cancers, exacerbates malnutrition.

• Fatigue and Weakness
• Chronic bleeding from tumors can cause persistent tiredness due to anemia, systemic inflammation, and increased energy expenditure for cancer treatment, resulting in reduced oxygen-carrying capacity.

• Loss of Appetite and Nutritional Deficiencies
• Tumor-related metabolic alterations can suppress hunger.
• Malabsorption syndromes may occur if the tumor affects the small intestine, thereby leading to deficiencies in essential vitamins and minerals.

• Bloating and Nausea
• Tumors causing partial obstruction can result in bloating and discomfort, particularly after meals.
• Delayed gastric emptying and intestinal motility disturbances can lead to persistent nausea.

• Intestinal Obstruction (Advanced Cases)
• Complete obstruction: Severe abdominal cramping, nausea, vomiting, and the inability to pass stool or gas.
• Bowel perforation (in extreme cases): Can lead to peritonitis, a life-threatening emergency requiring immediate surgery.
  

Intestinal Cancer Causes

Genetic Factors

• Family History: Individuals with a firs t-degree relative diagnosed with colorectal cancer have a higher risk.
• Inherited Syndromes: Conditions like Lynch syndrome (Hereditary Nonpolyposis Colorectal Cancer, HNPCC) and Familial Adenomatous Polyposis (FAP) significantly increase risk.
• Gene Mutations: Mutations in APC, KRAS, TP53 and SMAD4, as well as mismatch repair (MMR) genes, contribute to tumorigenesis.

Chronic Inflammatory Conditions

• Ulcerative Colitis & Crohn’s Disease: Long-standing inflammation can lead to DNA damage and malignancy.

Dietary & Lifestyle Factors

• High Consumption of Red & Processed Meat: These foods contain Contains carcinogens like heterocyclic amines and polycyclic aromatic hydrocarbons.
• Low Fiber Diet: Fiber promotes bowel motility and reduces exposure to toxins.
• Obesity & Sedentary Lifestyle: These factors Increases inflammation and insulin resistance, promoting cancer growth.
• Smoking & Heavy Alcohol Consumption: Tobacco carcinogens and ethanol metabolism generate DNA-damaging agents.

Metabolic & Microbiome Factors

• Type 2 Diabetes: Hyperinsulinemia and chronic inflammation contribute to tumor progression.
• Gut Microbiome Dysbiosis: Imbalance in gut bacteria, particularly the overgrowth of Fusobacterium nucleatum, promotes inflammation and carcinogenesis.

Environmental & Medical Factors

• Carcinogen Exposure: Prolonged exposure to industrial chemicals, pesticides, or radiation increases the risk.
• Previous Radiation Therapy: Radiation in the abdominal region may damage DNA and trigger cancer.

Early detection through regular screening (such as colonoscopy, stool tests, genetic testing) is crucial for prevention and better outcomes.

Intestinal cancer diagnosis

Accurate diagnosis is crucial for improving the patient’s prognosis and determining the most effective treatment plan for intestinal cancer. The diagnostic process involves a combination of clinical assessment, advanced imaging, and pathological analysis.

Medical History and Physical Examination

A thorough initial evaluation helps identify risk factors and early symptoms.

• Medical History: A detailed discussion covering persistent symptoms such as unexplained weight loss, changes in bowel habits, abdominal pain, rectal bleeding, and fatigue. Dietary habits and family history of colorectal or gastrointestinal cancers are also assessed.
• Physical Examination: Includes palpation of the abdomen to detect any lumps, tenderness, or organ enlargement. Signs of anemia (such as pale skin and fatigue) may indicate chronic blood loss from a gastrointestinal tumor.

Endoscopic Procedures

Endoscopic techniques allow direct visualization of the intestinal lining, aiding in early detection and biopsy collection.

• Colonoscopy: In this procedure, a colonoscope is inserted into the colon to examine if for polyps, tumors, or abnormal tissue. Biopsies can be taken during the procedure for histopathological evaluation.
• Upper Endoscopy (Esophagogastroduodenoscopy–EGD): Helps visualize the esophagus, stomach, and duodenum. This is particularly useful for detecting small intestinal cancers in the proximal region.
• Capsule Endoscopy: A small, pill-sized camera is swallowed to capture detailed images of the small intestine, which is particularly useful for identifying tumors or obscure gastrointestinal bleeding that other methods may miss.

Imaging Tests

Advanced imaging techniques would help to determine tumor size, location, and potential spread to nearby or distant organs.

• CT Scan (Computed Tomography) and MRI (Magnetic Resonance Imaging): These scans Provides detailed cross-sectional images to assess tumor invasion, lymph node involvement, and distant metastases.
• PET Scan (Positron Emission Tomography): Uses radioactive glucose tracers to detect active cancerous areas, aiding in staging and treatment planning.
• Barium X-ray (Small Bowel Follow-Through): Involves swallowing a barium contrast material, which coats the intestinal lining and highlights abnormalities such as strictures, tumors, or polyps on X-ray imaging.

Biopsy and Pathological Analysis

A biopsy is the gold standard test in confirming an intestinal cancer diagnosis

• Tissue Sample Collection: A small piece of abnormal tissue is obtained during endoscopy, surgery, or image-guided procedures.
• Histopathological Examination: The sample is analyzed under a microscope to identify cancerous cells, determine the cancer subtype (such as adenocarcinoma, or lymphoma, neuroendocrine tumor, etc.), and assess its aggressiveness.
• Molecular and Genetic Testing: Advanced tests like molecular and genetic testing usually done to identify genetic mutations, such as KRAS, BRAF, or MSI (microsatellite instability), which can guide targeted therapy.

Blood Tests

Blood tests usually help in assessing the overall health, understand indirect signs of cancer, and support in treatment response.

• Complete Blood Count (CBC): Identifies anemia, which may result from chronic blood loss due to a gastrointestinal tumor.

Tumor Markers

Some of the tumor markers are as mentioned below

• Carcinoembryonic Antigen (CEA): Elevated levels are seen in colorectal and intestinal cancers making it useful for monitoring treatment response.
• CA 19-9: May be elevated in advanced cases, though it is not specific to intestinal cancer.
  

Intestinal Cancer Treatment

The treatment of intestinal cancer depends on the type of intestinal cancer, its stage, and the patient’s health. Options include:

• Surgical Treatment: Surgical treatment is one of the primary choice of treatment, especially in case of early diagnosed cancer. Some of the cancer types are: 
• Segmental Resection or Colectomy: Removal of the cancerous segment of the intestine.
• Laparoscopic Surgery: Minimally invasive surgery with quicker recovery times and reduced complications.
• Stoma Creation (Colostomy/Ileostomy): Performed in some cases after tumor removal, particularly for rectal cancers.

• Radiation Therapy: Radiation therapy can be given as an adjuvant therapy along with chemotherapy and surgery. Some of the important types are:
• External Beam Radiation: Used in rectal cancer and locally advanced cases.
• Intraoperative Radiation Therapy (IORT): Targets residual cancer cells during surgery.

• Chemotherapy and Targeted Therapy: Systemic chemotherapy and immunotherapy options, including checkpoint inhibitors are used for advanced-stage cancers.
  

Intestinal Cancer Survival Rate

The survival rate for intestinal cancer varies based on the type and stage. For small intestine adenocarcinoma, the 5-year survival rate is around 70–80% for localized cases, 50–60% for regional spread, and 10–20% for distant metastases, with an overall survival of 30–40%. Colorectal cancer has a better prognosis, with a 90% survival rate for localized cases, 70% for regional spread, and 15–20% for distant metastases, with an overall survival rate of 65%. Early detection and appropriate treatment significantly improve outcomes.