Insulinoma is a cancer of the pancreas, which can cause affected dogs to have a poor exercise tolerance or even collapse. Early diagnosis of this condition is essential to provide the most effective therapy.
An insulinoma is a special kind of cancer of the pancreas. These cause symptoms by producing excessive amounts of insulin, which results in the animal suffering low blood sugar levels and feeling light-headed and weak. Animals with insulinomas can also show symptoms such as reduced ability or enthusiasm to exercise and even fainting, particularly after long periods without eating.
Insulinomas can be very challenging to diagnose because:
- The symptoms are not specific to this condition, and
- Blood tests might suggest there is a relative imbalance between insulin and blood glucose but are rarely conclusive.
If your vet suspects that your pet may have an insulinoma on the basis of the symptoms it shows they will need to take some blood tests to confirm exactly what is going on. It is also important to check for evidence of spread of the cancer using abdominal ultrasound and chest X-rays.
Ultimately the diagnosis is made by surgical biopsy but clearly your vet needs to be confident of what they would find in order to perform this operation. Oddly, insulinoma is diagnosed much more frequently in the summer; in one study 9 out of 10 insulinoma cases treated over the course of a 5 year period were diagnosed between May and September!
Patients with insulinoma are treated according to the severity of their problem. In animals where there is an apparently solitary lump in the pancreas, surgery can be performed to remove the part of the pancreas containing the cancer.
If the cancer has already spread to the lymph nodes or the liver, surgery is unlikely to have a beneficial effect and so treatment is aimed at controlling the signs of disease with medication. Patients who are not good surgical candidates receive medical therapy, initially solely with a kind of steroid called prednisolone.
Life expectancy following a diagnosis of insulinoma is related to how badly affected the individual is. If surgery has been performed the development of post-operative complications might significantly influence life expectancy.
Previous reports in the literature describe average life expectancies of approximately 1 year for patients undergoing surgery and 2½ months for medical management. A more recent UK study reported outcomes that appeared to be significantly improved by comparison, with an average life expectancy following surgery of approximately 18 months. For patients who have achieved normal blood glucose control post-operatively, the average survival time was in excess of 3½ years. This compares reasonably favourably with published estimates of up to 381 days.
It should also be remembered that patients receiving medical therapy, whether due to disease relapse after surgery or because surgery was not an option, can still enjoy a prolonged period of normal life. The average life expectancy for these patients in the UK study was 15 months from the time of institution of medical therapy.