The small intestine is responsible for the majority of nutrient absorption in the body. Despite its substantial length, cancer originating here is rare compared to malignancies found in the large intestine (colon). This rarity often contributes to a delayed diagnosis due to a low index of suspicion among medical professionals.
Incidence and Prevalence: Setting the Rarity Standard
Cancers of the small intestine are statistically uncommon, accounting for less than five percent of all cancers that occur within the gastrointestinal tract. In the United States, the disease represents only about 0.6 percent of all new cancer diagnoses annually. The age-adjusted incidence rate in the U.S. is approximately 2.1 to 2.3 cases per 100,000 people each year.
This incidence rate contrasts sharply with colorectal cancer, which has significantly higher annual case numbers. There are over ten times more diagnoses of large intestine cancer than small intestine cancer annually. The lifetime risk of developing this malignancy is low, estimated at about 0.3 percent for both men and women.
Small intestine cancer typically affects older adults, with the median age at diagnosis generally falling around 66 years old. Incidence rates are consistently higher for men than for women. While the overall incidence remains low, recent data indicates a slight but consistent increase in the rate of new diagnoses in developed nations.
Breakdown by Cancer Subtype
“Small intestine cancer” is an umbrella classification for four distinct types of malignancies, each arising from different cell lines within the intestinal wall. The statistical distribution of these subtypes determines which is the most commonly encountered in clinical practice.
Neuroendocrine tumors (NETs), previously known as carcinoids, are the most frequently diagnosed subtype in the United States, accounting for over 54 percent of cases. These tumors originate from hormone-producing cells and often grow slowly. Adenocarcinoma is the second most common type, making up roughly 30 to 40 percent of cases, and tends to be more aggressive.
The remaining cases are primarily split between lymphoma and sarcoma. Lymphoma, which develops from lymphatic tissue, accounts for around 15 to 20 percent of small intestine cancers. Sarcomas, which arise from connective tissues like muscle or fat, are the least common group, with gastrointestinal stromal tumors (GISTs) being the most prevalent form found here.
Survival Statistics and Prognosis
The prognosis for small intestine cancer is closely linked to the stage at which the disease is discovered, a pattern consistent with most cancer types. The overall five-year relative survival rate for all stages combined is approximately 71.1 percent. This figure represents the percentage of people who are alive five years after diagnosis compared to the general population.
Survival statistics show a marked difference based on how far the cancer has spread. When the cancer is localized (confined to the small intestine walls), the five-year survival rate is 85.6 percent. This rate drops to 79.6 percent if the cancer has spread regionally to nearby lymph nodes or tissues.
The prognosis becomes significantly less favorable if the disease has spread to distant organs, a stage known as metastatic cancer. For distant-stage disease, the five-year survival rate falls to 46.6 percent. Beyond staging, the specific cancer subtype also influences outcomes, with neuroendocrine tumors generally having a better prognosis than aggressive adenocarcinomas.