Prognosis

Primary tumor location and tumor size are the most relevant prognostic factors. Thus, appendiceal and rectal neuroendocrine tumors are mostly small tumors that almost never metastasize.4243 In contrast, thymus neuroendocrine tumors arise with distant metastases in about 30%4344 and gastric and small intestinal carcinoids in up to 100%.4546 In gastric neuroendocrine tumors, pathogenesis also determines prognosis. The multiple carcinoid tumors found in the case of hypergastrinemia with ECL cell hyperplasia (type I or II) have a much better prognosis than solitary tumors unassoci-ated with hypergastrinemia (type III).

Tumor size also predicts the risk of metastatic spread in neuroendocrine tumors, whereas in other gastrointestinal tumors the depth of tumor invasion is a better prognostic factor.47 The appendiceal, colon, and rectal neuroendocrine tumors are mostly small and usually do not metastasize. Generally, tumors smaller than 1.5 or 2 cm have a low risk of metastatic spread. However, size is less predictive of prognosis in small intestinal carcinoids. Even tumors smaller than the critical size of 1.5 cm may have nodal or distant metastases (Table 86-5).

Identifying molecular alterations or other factors that categorize patients with aggressive tumors could be of great clinical value, allowing more aggressive treatment.22 In general, all cytosolic and granular markers are found in well-differentiated endocrine tumors. In poorly differentiated neuroendocrine carcinomas, however, only cytosolic markers and synaptophysin are generally widely expressed.48 The presence or type of somatic MEN 1 mutation has not been correlated with disease phenotype and to date has no role for neuroendocrine tumors in clinical prognosis.49 Loss of

TABLE 86-5. Tumor Location and Tumor Stage in Carcinoid Tumors (n = 71)

Organ

Size and Pos.

Size and Pos.

Distant Metastasis

<1.5 cm

LN

>1.5 cm LN

Stomach

_

_

4

4

1/4 (25%)

Duodenum

3

0

Small bowel

5

1

17

16 (94%)

7/17 (41%)

Appendix

13

0

Rectum

3

0

T-

Bronchus

9

0

12

6 (50%)

2

Thymus

5

2 (40%)

1

neuropilin-2 expression in neuroendocrine cells has been shown to accompany tumor progression in neuroendocrine tumor.50 Moreover, MIB-1 antibody reacts with the Ki-67 nuclear protein associated with cell proliferation and has been used to profile tumor aggressiveness. Although studies of Ki-67 have been helpful in assessing the malignant behavior of neuroendocrine tumors, multiparametric approaches examining the full range of cyclins, cyclin inhibitors, factors controlling apoptosis, oncogenes, and tumor suppressor genes are essential to resolve this issue.51

The overall survival in all groups of neuroendocrine tumors is about 50% to 60% at 5 years, 30% to 40% at 10 years, and 25% at 15 years. Five-year survival rate in patients with a distant metastases is about 20%. Thus, neuroendocrine tumors have a moderately good prognosis, and long-term survival is possible even in advanced stages.

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