Small intestinal cancer: a population-based study of incidence and survival patterns in the United States, 1992 to 2006.

BACKGROUND

The etiology of cancers of the small intestine is largely unknown. To gain insight into these rare malignancies, we evaluated contemporaneous incidence and survival patterns.

METHODS

Using small intestine cancer data from 12 population-based registries of the Surveillance, Epidemiology and End Results Program, we calculated age-adjusted and age-specific incidence rates (IRs), IR ratios, and relative survival (RS) rates.

RESULTS

In total, 10,945 small intestine cancers (IR = 2.10/100,000 person-years) were diagnosed during 1992 to 2006, including carcinomas (n = 3,412; IR = 0.66), neuroendocrine cancers (n = 4,315; IR = 0.83), sarcomas (n = 1,084; IR = 0.20), and lymphomas (n = 2,023, IR = 0.38). For all histologic groups, males had significantly higher IRs than females, and distinct age-specific gender patterns were limited to intermediate-/high-grade lymphomas. Neuroendocrine cancer rates varied significantly by race, with rates highest among blacks and lowest among Asians/Pacific Islanders. Carcinoma IRs were highest among blacks; sarcoma IRs were highest among Asians/Pacific Islanders; and lymphoma IRs were highest among whites. Age-specific IR patterns were similar across racial/ethnic groups. During 1992 to 2006, duodenal cancer IRs increased more markedly than those for other subsites. RS varied little by gender or race. Neuroendocrine cancers had the most favorable RS, and carcinomas had the least favorable. The greatest improvement in 5-year RS from 1992 to 1998 to 1999 to 2005 was observed for sarcomas and lymphomas.

CONCLUSIONS

Distinct small intestine cancer IR patterns according to histologic subtype suggest different underlying etiologies and/or disease biology, with susceptibility varying by gender, racial/ethnic groups, and subsite. Temporal patterns support a possible role for diagnostic bias of duodenal cancers.

IMPACT

Future epidemiologic studies of small intestine cancer should consider histologic subtype by gender, race/ethnicity, and subsite.