Pocket Oncology (Pocket Notebook Series), 1st Ed.

APPENDIX AND SMALL BOWEL CARCINOMA

Jean K. Lee and Leonard Saltz

SMALL BOWEL CARCINOMA*

Epidemiology

• Small bowel malignant tumors are rare; approximately 8000 new cases & 1150 death annually in US

• Small bowel neoplasms account for approximately 2% of all GI tract CAs; <0.4% of all CA in US

• Recent ↑ in the incidence (14.8/100000) between 1994–2000 w/higher incidence in African-Americans w/slight male predominance (male to female ratio 1.5:1)

• Mean age at dx, 65 y

• Most common malignant small bowel tumors include adenoca (45%), carcinoid (29%), lymphoma (16%), sarcoma (10%) (SEER Program, NCI 1987)

Risk Factors and Pathophysiology

• No clear etiology known for most small bowel CAs; most small bowel adenoca arise from adenomas; likely multistep accumulation of somatic Mts from exposure to carcinogens w/in intestinal lumen

• Several hereditary CA syn a/w predisposition for small bowel adenoca at earlier age of onset (<10% cases):

HNPCC

FAP

Peutz–Jeghers syn

• Pts w/colon adenoca a/w ↑ risk of small bowel adenoca; conversely pts w/small bowel neoplasms w/higher incidence of 2° malignancies involving the colon, rectum, ampulla of Vater, endometrium, & ovary

• Role of chronic mucosal inflammatory states (chronic IBD including CD) in ↑ risk of small bowel adenoca & lymphoma

• Diet (red meat, smoked foods, EtOH intake), tobacco, obesity

• Majority of small bowel adenoca found in the duodenum; possibly due to metabolism of carcinogens in transit through small bowel or interactions w/pancreaticobiliary secretions & carcinogens; exception is CD w/>70% adenoca arising in the ileum; jejunum/ileum for Celiac disease

Clinical Manifestations

• S/s: Nonspecific nature of sx make early dx difficult; majority of pts have adv disease at dx

• Sx are vague & include abdominal pain, N/V, wt loss, anemia, GIB, intestinal obstruction

• Duodenal adenoca often p/w vomiting due to gastric outlet obstruction

Staging and Prognosis

• 5-y survival by stage in small bowel adenoca by SEER database:

Stage I 85%

Stage II 69%

Stage III 50%

• # of LN evaluated strong prognostic factor w/improved 5-y disease-specific survival in pts w/>8 LN evaluated:

Stage I 95%

Stage II 83%

Stage III 56%

• Additional prognostic factors include site of disease (worse for duodenal primaries compared to jejunum or ileum), presence of nodal & distant mets

• Poor prognostic indicators include positive resection margins, lymphovascular invasion, T4 tumor stage, extent of nodal disease, poorly differentiated histology

• In general, 5-y survival of pts w/small bowel adenoca are worse than for similarly staged colon CAs

Management

• Locoregional disease: If resectable (65–75% pts at dx), management w/wide segmental surgical resection of the 1° tumor & mesentery including regional LN; provides staging info regarding the need for adjuvant Rx (see below)

• Pancreaticoduodenectomy recommended for tumors involving the 1st & 2nd portions of duodenum. Adenoca involving the jejunum or proximal ileum treated by wide excision

• Right colectomy indicated for tumors in the distal ileum

• Adjuvant systemic Rx: Lack of prospective data for use of systemic adjuvant Rx; use of OX-based regimen (FOLFOX) recommended in node-positive, completely resected small bowel adenoca based on extrapolation from node-positive colon CA data showing survival benefit (see Colon Cancer section, MOSAIC trial)

• Unresectable or met disease: In general, systemic chemotherapy for small bowel adenoca based on tx established for metastatic CRC according to NCCN Guidelines for Colon CA

• No standard 1st-line chemotherapy regimen or NCCN Guidelines exist for adv small bowel adenoca due to lack of randomized prospective trials

• Systemic chemotherapy based on paradigm for Colon CA, w/5-FU plus platinum drug (FOLFOX, CAPOX, etc.)

• Palliative surgical resection of 1° tumor may be needed in adv cases to prevent bowel obstruction or bleeding

• RT may provide local control for tumors located in the duodenum; endoscopic duodenal stent an option for nonsurgical palliation of duodenal obstruction