Unfortunately, NETs are often not diagnosed before they metastasize.2 At diagnosis, disease extent varies according to location of the primary tumor (see chart).1
Disease extent of selected gastrointestinal and bronchial sites* at diagnosis1
Survival depends on stage and histology
Long-term data from the SEER database (1973-2004) show the malignant potential of NETs: Patients with well-differentiated grade 1/grade 2 neoplasms with distant metastases have a median survival of 33 months.1 The median survival of patients with distant metastases who have anaplastic NETs is only 5 months.1
Across all types of neuroendocrine neoplasms, prognosis seems to be dependent on both histology and disease extent. Well-differentiated grade 1 NETs generally are associated with less-aggressive behavior, grade 2 NETs have a more variable clinical course, and poorly differentiated grade 3 neuroendocrine carcinomas are characterized by extremely aggressive tumor biology and poor prognosis.3 In patients with distant metastases, for example, the 5-year survival probability for well-differentiated G1/G2 NETs is 35%; for patients with poorly differentiated neuroendocrine carcinomas, it drops to just 4%.1
The presence of distant metastases is a particularly important predictor of outcome in patients with pancreatic NETs. One study found that the likelihood of death after resection of the primary tumor was 2-fold higher in patients with distant metastases than in patients without.4 Other researchers have reported that survival duration was decreased in patients who have distant disease compared with those who have localized disease (hazard ratio = 3.40).5
Metastatic potential also varies between G1 and G2 bronchial NETs; although the former are associated with significantly better survival,6 they still are considered to be malignant tumors with no histologic characteristics that are reliable predictors of metastatic behavior.7
Survival rates depend on many factors
Survival can, however, vary widely across specific types of NETs.
- Median 5-year survival for patients with GI NETs with distant metastases range from 5 months for colon tumors to 56 months for ileal/jejunal tumors1
- Metastatic pancreatic NETs are considerably more malignant, with a median 5-year survival of only 23 months among patients with distant metastases1
- Median 5-year survival among patients with well-differentiated lung NETs with distant metastases is only 16 months8
It is important to note, however, that survival rates vary across studies, and results from institutional series tend to report longer survival times than population-based studies, such as SEER. Overall, reliable data about NETs are difficult to obtain, because they typically are underreported. For example, a significant number of NETs are not classified using the International Classification of Diseases for Oncology (ICD-O-3) codes associated with carcinoid tumors.1
The table below shows the most recent survival times and 5-year survival rates reported by the following SEER program database for all NETs according to disease grade and stage:
The variation in median survival duration based on extent of disease underscores the importance of early diagnosis and use of the correct combination of tools to determine tumor specifics. Physicians should also consider leveraging the expertise of related specialists in both diagnosis and ongoing management to help improve patient outcomes.
The NET Alliance™ recognizes the serious nature of this disease and the importance of actively managing it.
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