Patho physiology: Carcinoid tumors are a type of neuroendocrine tumor, which means they come from cells of the nervous and endocrine system, and can produce hormones. When they secrete excess hormones such as histamine and serotonin, they can cause symptoms such as flushing, stomach cramps, and diarrhea. This is called carcinoid syndrome. When these tumors spread to the liver, patients usually begin to develop malignant carcinoid syndrome. In fact, this syndrome develops when vasoactive substances produced by a carcinoid tumor escape hepatic degradation and gain access to the systemic circulation.Carcinoids arising in the stomach are usually associated with low gastric acid production, a condition termed hypochlorhydria or achlorhydria. These tumors rarely become malignant and never metastasize, but they sometimes produce histamine.Carcinoid tumors arising in the lung generally produce serotonin, gastrin, adrenocorticotropic hormone (ACTH), and histamine. Carcinoids that develop outside the appendix are often malignant, while tumors developing in the appendix are usually benign if smaller than 2 cm in diameter. Rectal carcinoid tumors often produce polypeptides (PPs), polypeptide Y, neuropeptide Y, and other peptides, but none of the patients with this disease location have symptoms related to the production of such molecules. Few patients have liver metastases, but if they do have liver metastases, they do not have hormone-related symptoms.
Treatment: Somatostatin analogues have been the treatment of choice in symptomatic patients with carcinoid tumors, but more recent studies have indicated a cytostatic effect of somatostatin analogues. Tumor-targeted radioactive treatment based on somatostatin analogues is now under clinical evaluation. Preliminary data indicate interesting clinical potentials. If metastasis of carcinoid tumor has occurred and in cases where surgical excision is not suitable, consider treatment with currently recommended chemotherapy. Chemotherapeutic agents currently used in clinical trials to palliate metastatic carcinoid disease include the following: Alkylating agents, Doxorubicin, 5-Fluorouracil, Dacarbazine, Actinomycin D, Cisplatin, Etoposide, Streptozotocin, Interferon alfa, Somatostatin analogs with a radioactive load • A combination of the agents listed above is typically used.
Research: Cells of the human bronchial carcinoid cell line NCI-H727 and the human pancreatic carcinoid cell line BON-1 were treated with increasing concentrations of imatinib using standard procedures to assess in vitro growth-inhibitory activity. A clinical trial using a two-stage phase II design to assess the response rate and safety profile of imatinib at a dose of 400 mg given twice daily in patients with advanced carcinoid tumors was completed. In both cell lines, there was a dose- and time-dependent cytotoxic effect. The clinical trial enrolled 27 evaluable patients. Median duration on trial was 16 weeks. One patient had a partial response, 17 had stable disease, and 9 had progressive disease by the Response Evaluation Criteria in Solid Tumors criteria. Median progression-free survival time was 24 weeks. Median overall survival is 36 months. Seven patients who achieved a biochemical response had a superior progression-free survival time compared with patients without biochemical response (115 weeks compared with 24 weeks; P = 0.003). An increase in plasma basic fibroblast growth factor was associated with a shorter progression-free survival duration (P = 0.02) Our data suggest that imatinib is active in vitro and has a modest clinical activity in carcinoid patients. Changes in tumor markers may help select patients who are likely to benefit from therapy.
Statistics: Of 26665 lung cancers registered during the period, 265 (1%) had carcinoid tumors, of which 11 were diagnosed coincidentally at autopsy. In the remaining 254 patients, TCs were found in 188 cases, and ACs were found in 59 cases; seven cases had unclassifiable carcinoids. Of the 217 resected tumors, 173 (80%) were TCs. General surgeons performed 94 resections, including 11 of 17 pneumonectomies. All six bronchial resections were performed by thoracic surgeons. Of the 33 operated patients who died during follow-up, 18 had metastatic carcinoid tumors, of which 10 (56%) were ACs. In 37 non-resected patients (15 with AC and seven with unclassifiable histology), metastatic or locally advanced disease (N=21, 12 of which were ACs) was the main cause of inoperability and death. Five-year survival for all patients was 92% for TC and 66% for AC; for resected patients, the survival rates were 96% and 79%, respectively. All incidence rates (per 100,000 population per year) extracted from 1993 to 2004 were age-adjusted using the US 2000 standard population for both databases and presented in terms of site, sex, and race. To further examine trends in NET disease, incidence rates were calculated for separate time periods (1993-1997 and 2000-2004). The observed 5-year survival was calculated using the actuarial method.16 Tumors were staged as localized (localized to organ of origin), regional (local lymph nodes and nearby organ invasion), distal (disseminated disease), or unknown extent of disease