-Term given to an embryologically related groupof tumours of endocrine organs. They are believed to arise from neuroendocrine cells,
which are derived from neural crest,and, whose normal function is to serve at neuroendocrine interface.
-APUD= amine precursor uptake and decarboxylation. -Tumours of this system = APUDomas; secretehormone of the tissue of origin -The term was coined in about 1974; has since been revised and called NEUROENDOCRINEGASTROENTEROPANCREATIC TUMOURS;
Cells with these properties have been grouped together as the APUD system.
They contain characteristic granules on electron microscopy
They secrete polypeptides or amines or both
The cells included here are:
The chromaffin cell system- These are found in the adrenal medulla and in association with the paravertebral plexuses.
The non-chromaffin cells of the paraganglia (Carotid body, glomus jugulare).
The argentaffin (Kultschitzky) cells.( found in the intestine). Similar cells occur in the salivary glands, pancreas, and bronchial mucosa. The argyrophil cells. These are widely distributed in the intestine.
Neural crest cells are a transient , multi- potent,migratory cell population unique to vertebrates that give rise to a diverse cell lineage including melanocytes,craniofacial cartilage and bones,smooth muscle , peripheral and enteric neurons and glia.
EMBRYOLOGY OF NEURAL CREST CELLS:-
After gastrulation,neural crest cells are specified at the border of the neural plate and the non neural ectoderm. During neurulation,the border of the neural plate,also known as the neural folds,converge at the dorsal midline to form the neural tube. Subsequently,neural crest cells from the roof plate of the neural tube undergo an epithelial to mesenchymal transition,delaminating from the neuroepithelium and migrating through the periphery where they differentiate into varied cell types.
EMBRYOLOGY OF NEURAL CREST CELLS:-
Neuroendocrine tumors are:
CHARACTERISTICS OF NET’s
-Rare-Usually small, <1cm-Slow growing over months to years-Usually metastasize before becomingsymptomatic, often when tumour > 2cm-Expression is episodic, may be silent for years- often misdiagnosed-Complex diagnosis requiring advanced radiographic studies.
-In the past all NET’s were termed carcinoid; -Has since been classified into: 1. CARCINOID 2. NON-CARCINOID -According to WHO 5 major categories: i. well differentiated endocrine tu’s ii. Well differentiated endocrine ca’s iii. Poorly differentiated endocrine ca’s iv. Mixed endocrine and exocrine ca’s v. Neuro-endocrine – like lesions
pancreas -If tumour can still be localized – resection -Preoperative planning: TPN containing amino- acids, (steroids, Zn supplementation, Abics: Useful for the rash) Medical: -Long term chemotherapy: streptozotocin +/- 5-
attempted -Even with metastasis debulking is indicated Medical: -Long term octreotide useful for control of diarrhoea as well as benefit with tumour arrest or regression. - Chemotherapy is rarely of benefit
They originate in the enterochromaffin cells of the intestine and have the ability to produce various peptides and hormones.
Previously categorised by their embryological origin – foregut, midgut & hindgut.
Revised classification has taken into account tumour location, histological grade and proliferative index
Neuro-endocrine tumours of the gastrointestinal tract (carcinoids) are rare tumours
Origin of carcinoid tumors
Digestive sys-tem 64%
small intestinecolon & rectumstomachothers
Distribution in the GIT
-Typical small neoplasm occurring in submucosa
-Growth of the tumor is slow; vast majority are < 1cm ( 5% > 2cm)
-It grows outward leaving the mucosa intact -As it reaches the serosa it can cause a
desmoplastic reaction and lead to kinking of the bowel
Carcinoid syndrome is almost uniquely associated with midgut carcinoids (neuro-endocrine tumours of the gastrointestinal tract)
Carcinoid syndrome was first described by Thorson and co-workers in 1954
Systemic symptoms are caused by an excess of biogenic amines, peptides and other factors (serotonin, tachy- and bradykinins and histamine) in the circulation only after liver metastases.
Diarrhoea (±80% of patients), mainly caused by serotonin excess, also histamine, kallikrein, prostaglandin, substance P and motilin
Flushing (± 94% ), linked to several humoral factors – tachykinins, serotonin & histamine. Provoked by e.g. nuts & cheese, certain drugs & alcohol
Carcinoid heart disease (± 40% ), characterised by so-called ‘plaques’ at the right side of the heart with involvement of the tricuspid and pulmonary valves and endocardium
Pellagra (± 5% ) characterised by dermatitis,
diarrhoea & dementia – result of niacin deficiency
Intermittent bronchial obstruction (10%) often accompanies flushing,
Carcinoid crisis – rare, potentially fatal – provoked by anaesthesia /surgery if not treated sufficiently with somatostatin analogues
Carcinoid tumours less than 1cm in diameter & confined to the mucosa and submucosa generally remain subclinical for years.
Larger than 1 cm – generally malignant & have metastasized to regional lymph nodes and later to the liver and other locations.
Patients have generally been complaining for years of intermittent abdominal discomfort, erroneously diagnosed as a functional disorder such as irritable bowel.
Intermittent intestinal obstruction due to kinking of the small bowel can occur at a later stage as a result of the desmoplastic reaction in the mesentery
Incidence of midgut (neuro-)endocrine tumours is ± 0.2-2/100 000 population/year
Equal distribution between males & females Incidence is higher in black than white people Most prevalent location is the terminal ileum
close to the ileocaecal valve Is often multiple In up to 15% of patients other malignancies such
as gastrointestinal adenocarcinoma and breast cancer have been demonstrated
Biochemical diagnosis includes measurements of serum chromogranin A and urinary excretion of 5-HIAA. Estimation of plasma serotonin is facultative
Tumour imaging - transabdominal ultrasound is the initial imaging
procedure in most patients with metastasized carcinoids.
◦ Contrast-enhanced three-phase CT or MRI followed by needle biopsy for pathology can be performed.
◦ In-pentetreotide scintigraphy is positive in 80-90% of patients
◦ Echocardiography is mandatory in patients with carcinoid heart disease
SURGERY: -Based on site, size and presence/absence
of metastasis. -<1cm: no nodal involvement – segmental
resect. ->1cm: + nodes – wide excision of bowel
and mesentery. -For tumours with widespread metastasis,
Sx is still of benefit.
-Is directed to patients with malignant carcinoid syndome and those with widespread metastasis. -Somatostatin analogues ( sandostatin): relief of symptoms (diarrhoea + flushing); also tumor regression (17%) -Serotonin receptor antagonists: used with limited
success. (methysergide no longer used) -Cytotoxic chemotherapy: agents used Streptozotocin + 5-FU/cyclophoshamide (33%)
Targeted chemotherapy agents have been approved in Pancreatic Neuroendocrine Tumors by the FDA based on improved progression free survival
EVEROLIMUS is labelled for patients with unresectable,locally advanced or metastatic disease. The safety and effectiveness of everolimus in carcinoid tumors have not been established.
SUNITINIB is labelled for treatment of progressive,well differentiated PNETs in patients with unresectable,locally advanced or metastatic disease
Platinum & Etoposide combination is sometimes given in pulmonary carcinoids.
This is a type of radioisotope therapy where the tumor is treated intravenously with a peptide or hormone conjugated to a radionuclide or radioligand. This is also called as peptide receptor radionuclide therapy or hormone delivered radiotherapy and can attack all lesions in the body .
Typically radiolabelling octreotate to lutetium 177, yttrium 90 or indium 111 is done.
This is a highly targetted and effective therapy with minimal side effects in tumors with high levels of cell surface somatostatin receptors. Radiation is taken up at the sites of tumor or excreted in urine.
HORMONE DELIVERED RADIOTHERAPY
Metastasis to liver can be treated by hepatic artery treatments based on the observation that tumor cells get nearly all their nutrients from the hepatic artery. Hepatic artery embolization or chemoembolization occludes the blood flow to the tumor achieving significant shrinkage in over 80% of cases.
Selective internal radiation therapy deliver radioactive microsphere by injection into the hepatic artery.
Radiofrequency ablation is used when a patient has relatively few metastases.
Cryoablation has been less successful for GEP-NETs than RFA.
EPOTHILONE B:- A novel cytotoxic agent It is a potent anti angiogenesis agent. It acts by blocking the polymerization of
tubulin in blood vessels Action is similar to that of taxane More suitable for slow growing tumors.
-Best prognosis of all small bowel tu’s -Resection of localized tu – 100% survival
rate -65% for patients with regional disease; - 25-35% for patients with distant
multiple endocrine neoplasia type 1 (MEN1) multiple endocrine neoplasia type 2 (MEN2) von Hippel-Lindau (VHL) disease neurofibromatosis type 1 tuberous sclerosis Carney complex
Immediate onset of a debilitating and life-threatening condition associated with carcinoid syndrome
May occur spontaneously or may be precipitated by anesthesia, chemotherapy, infection, stress, catecholamines, tumor manipulation or embolization procedures
Symptoms include prolonged severe flushing, diarrhea, hypotension,tachycardia, severe dyspnea, peripheral cyanosis and sometimes hemodynamic instability.
Appropriate precautions include immediate therapy and close monitoring before, during and after surgical treatment.
Prophylactic administration of octreotide must be given by continuous intravenous infusion at a dose of 50 μg/h for 12 hours prior to and at least 48 hours after the procedure to prevent a cardiovascular carcinoid crisis.
Carcinoid Crisis - Prevention
For anaesthetic purposes,patients with carcinoid tumors should be regarded as suffering from a multi-system disease and so require thorough pre-planning f/b post operative management in a high dependency environment.
Main aims are to maintain normal haemodynamics and prevention of occurrence of carcinoid crisis.
Principles of anaesthetic management for carcinoid
History and Examination: signs/symptoms suggestive of ongoing
There is a risk of hypo or hypertension developing intraoperatively
The response to inotropes or vasopressors is unpredictable. Norepinephrine and epinephrine can be hazardous in carcinoid patients
Practically,small doses of phenylephrine has been helpful.
Aprotinin – a kallikrien antagonist has a significant place in symptomatic control peroperatively.
If prolonged vasocontriction is required,vasopressin can be used.
Vasoactive hormone release intraop is best treated with iv boluses of 20-50microgram of octreotide titrated to hemodynamic response
Blood loss monitoring is very important. For prolonged hypertension,labetolol
infusion have been used.
As with the intra-operative management, post-operative care focuses on the provision of stable cardio-respiratory conditions and adequate analgesia.
High-dependency care is recommended. Ongoing hormonal control of the tumour is important as post-operative crisis are possible and surgery may have been aimed at reducing the bulk of carcinoid tumour present, rather than eliminating it.
Intravenous and then subcutaneous octreotide follow-up will help control any further hormone release and there may well be residual, hormonally active tumour remaining.
Forty-eight hours of invasive monitoring, analgesia and fluid management may be required to ensure safe recovery from the surgery.
POST OPERATIVE MANAGEMENT
There has been a review of the biology of enteroendocrine tumours over the past 1-2 decades, and significant advances have been made. There is a need for enhanced awareness of theheterogenous features of these tumours as well asmultiplicity of modalities available for their treatment. Increasing acceptance of the more aggressive and
customized treatment with recognition that favorable responses in these pts result from sequential use of multiple modalities.
Miller’s Anaesthesia-7th edition Churchill and Davidson-5th & 6th editions Oxford journal- CEACCP 2011;11(1):9-13 Int Anesthesiol Clin 1997;35(4):129-42 http://pharmalicensing.com