What are the first signs of cancer?

Cancer can arise in any part of the body and produce a wide variety of clinical signs. Some of the changes are specific, such as an obvious lump, but others are more vague and can mimic other disease processes. Coughing, vomiting, diarrhoea, lameness, weight loss, depression, fits, loss of appetite and even skin lesions can all be indicators of underlying cancerous processes. If the patient is middle-aged or elderly and does not respond to initial symptomatic treatment then your vet may become suspicious of cancer at an early stage in the illness, but young animals may also be affected and the possibility of cancer cannot be discounted on the basis of age. If your vet suspects cancer then he or she will perform further diagnostic tests to confirm or refute the diagnosis. If a positive diagnosis is made then more precise tests may be necessary in order to decide on the most appropriate treatment. It is important that early and accurate diagnosis is made since many forms of cancer in dogs and cats are treatable and may even be cured with appropriate treatment.

What types of diagnostic test can be performed?

Blood tests - some types of cancer cause direct changes in the blood which can suggest or confirm a diagnosis, such as leukaemias (cancers of white blood cells). Blood tests are also important to detect secondary infections and anaemia which may require extra treatment and to check the functioning of important body systems in older patients. During treatment, repeated blood samples may be required to check that treatment itself is not causing problems.

Cytology - this is the examination of cells using a microscope to identify their nature. The cells are aspirated from the affected area (eg a swollen lymph gland) using a fine needle, a procedure which is almost painless and is usually performed with the patient conscious. A good example would be aspiration of cells from a skin lump to differentiate between a benign fatty accumulation or lipoma and a more serious, cancerous growth.

Biopsy - this is the removal of a larger piece of solid tissue and is necessary in cases where cytology has failed to give a diagnosis or if the lump is hard and cannot be penetrated by a fine needle. Biopsies may be performed surgically, or using special biopsy devices. The procedure is normally carried out under local or general anaesthesia. Again, the sample is examined microscopically.

Endoscopy - this is a means of looking directly inside a body cavity using a long, narrow rigid or flexible telescope called an endoscope. Cancerous masses can be sen and biopsied using special pincer-like attachments, avoiding the need for open surgery. Areas of the body commonly examined in this way include the throat and windpipe, the stomach, the large bowel, the bladder and the nose. The Animal Health Trust is pioneering the use of endoscopy for looking inside the chest of dogs, a procedure still relatively new in human medicine.

Diagnostic imaging - this covers methods of obtaining pictures of the inside of the body, using X-rays, ultrasound, radioactive materials and CT or MRI scanning.

How does diagnostic imaging help in the diagnosis of cancer?

Radiography - is usually the first technique which is used, and can be performed in most veterinary practices. X-ray pictures (radiographs) show the internal structures of the body and will show some deformities of organs that cannot be felt. Bone cancers in particular can often be detected at a very early stage since their radiographic appearance is often quite characteristic and easy to differentiate from benign processes such as arthritis. Radiography is also very useful for looking at the lungs, since they contain air, which appears black on the radiographs, and outlines solid structures clearly. However soft tissues such as muscle and liver appear a uniform grey even when they contain abnormal areas.Radiography is used to delineate a known abnormality or to check other parts of the body, usually the lungs, for secondary tumours which may have spread from the first lesion. Radiography can also be used to monitor the progression or reduction of a known cancer over period of time.

Ultrasound - allows visualisation of the internal structure of soft tissues, and most people are familiar with its use in examining human babies before birth. It can differentiate between different types of tissues and also between fluid and solid matter. Its importance in cancer diagnosis lies in its ability to detect small abnormalities deep within organs and to allow precise, 'ultrasound-guided' aspirate or biopsy to be performed. A good example would be aspiration of cells from small nodes in the spleen to differentiate between benign reactive nodules and cancers; without ultrasound guidance there would be a good chance of aspirating normal splenic cells.

Scintigraphy - involves injection of small volumes of radioactive chemicals into the body , which collect in areas of cancer and other tissue abnormalities which are too small to be seen with other techniques. Examination of the patient using a detector called a 'gamma camera' allows these hidden lesions to be identified. In man scintigraphy is used particularly to detect early secondary tumours in the skeletal system. Scintigraphy is proving to be of enormous benefit at the Trust, both for clinical and research applications. In effect it provides an 'early warning system' when evaluating the health status of small animals and horses alike.

What is Scintigraphy?

Scintigraphy is a diagnostic technique which uses a sophisticated camera to obtain two-dimensional images showing the areas in the body which take-up an injected radio-labelled isotope. Using advanced computer technology, these images can then be analysed to provide both qualitative and quantitative information. If, for instance, illness or injury is causing increased metabolic activity or blood flow, the area involved will emit a higher level of gamma radiation (seen on the image as a 'hot spot').

The amount of radiation emitted by the animals during scintigraphy is much lower than that used in radiography. However, every precaution is taken to ensure the safety of the operators and the animals concerned. All treated animals are placed in dedicated kennels or stables for a minimum of hours after the scan. Following our relocation programme, the Centre for Small Animal Studies and the Centre for Equine Studies are now on one site and able to share facilities. This is particularly relevant in relation to scintigraphy which, necessarily, requires expensive equipment but can be applied to horses as well as small animals. The Animal Health Trust has the potential to become the world's leading centre for veterinary scintigraphy because of its combination of: The most sophisticated equipment available, supported by state-of-the-art computer technology. An agreement with the manufacturers that all hardware and software will be upgraded constantly for at least 5 years A dedicated building housing a scintigraphy suite which was specifically designed for horses and small animals A level of expertise which is second to none.

Why Scintigraphy?

The most essential element of effective veterinary care is the ability to diagnose abnormal conditions quickly and accurately. Sometimes this is possible by undertaking a simple physical examination. In other cases, it may be necessary to use such techniques as radiography or ultrasound scanning. These enable us to look for anything unusual in the structure and shape of an affected area. However, certain conditions will not manifest themselves in this way, or at least not until they have reached advanced stages when treatment is less likely to be successful. The advantage of scintigraphy is that it allows us to detect sub-clinical signs of damage. Scanning can provide visual information about function, such as blood flow or tissue turnover. Such an indication of increased activity in a specific area allows diagnosis of a range of conditions at a sufficiently early stage to improve the success of treatment considerably.

Applications of scintigraphy

Abdominal abscesses
One of the conditions most likely to be detected by this technique is the presence of abdominal abscesses. This is a fairly common occurrence but it is very difficult to diagnose by traditional means until the abscess has grown to a size where successful treatment is jeopardised. Even if clinical signs indicate the early presence of such an abscess, localisation is far from easy. Scintigraphy, however, will detect the area of increased activity and identify the exact position of an abscess. This provides a means of differential diagnosis in, for example, cases which present with fever of unknown origin. If it is assumed initially that this has a virological cause, valuable time may be lost before appropriate treatment can be implemented.

Thyroid disorders
Scintigraphy is particularly valuable in conditions which do not, necessarily, result in any morphological abnormality. Hyper- or hypo-thyroidism, for example, can be detected much earlier using scintigraphy than by any other method. Lameness Horses are referred to the Trust because they display signs of lameness with no obvious diagnosis. Many are suffering from, for example, joint disease or stress fractures. In the early stages, it is impossible to detect these from X-rays or ultrasound. However, scintigraphic scans can identify the precise area of sub-clinical inflammation. This enables medical or surgical treatment to be implemented at an early stage and to a definitively targeted area. Without this diagnostic aid, veterinary surgeons often have little option but to administer systemic anti-inflammatory drugs. The ability to confine treatment to the affected area makes such treatment more effective and reduces the likelihood of side effects. Cancer Investigations have indicated a great potential for the use of scintigraphy in the early detection of tumours in dogs and cats. Perhaps more than any other illness, cancer responds far more favourably to early treatment than to that instituted after the tumours have become large enough to be apparent on scans or X-rays.

Exercise induced pulmonary haemorrhage (EIPH)
One of the most challenging problems to equine veterinary science is the high proportion of horses which 'bleed' after competing in athletic events. This condition, known as exercise-induced pulmonary haemorrhage, affects over 50% of competition horses. However, there is no means of quantifying this problem and, therefore, it is difficult to assess its severity. Before any progress can be made in terms of prevention or therapy for the condition, this must be addressed. The Horserace Betting Levy Board is currently funding a project at the Trust to develop a means of quantifying the bleeding. This will involve the radioactive labelling of red blood cells. The Animal Health Trust has an international reputation for developing innovative methods of diagnosis and treatment.

CT and MRI scanning -produce finely-detailed cross-sectional images of the body which yield far more information about the tissues than do the other imaging techniques. The Animal Health Trust has its own MRI scanner (the first veterinary scanner in Europe) and uses it particularly to diagnose brain tumours and to map out the extent of other cancers before radiotherapy or major surgery. Brain tumours cannot be diagnosed without the use of CT or MRI scans and so the introduction of scanning to veterinary diagnosis has opened up a whole new area of diagnosis and treatment. For cancers elsewhere MRI allows accurate treatment planning and just as importantly shows if surgery is unlikely to be successful, preventing the patient from undergoing an inappropriate procedure.

Treatment
What should I do if a find a lump on my pet?

Not all lumps turn out to be tumours but it is important to ask your veterinary surgeon to have a look when you first notice one. A small tumour, even a cancer, is more likely to be cured if it is treated early. A biopsy may be necessary to determine the exact nature of the lump.

Can tumours in pets be treated?

Although 1 in 3 dogs will develop a tumour the majority, including many that are cancerous, can be cured if caught early. Some tumours, while not curable, may be kept under control for a good period of time to allow the pet to enjoy a normal, happy quality of life. Unfortunately, there are some tumours that are too advanced for any treatment and euthanasia is often the kindest option.

What types of treatment can be used?

There are several ways to treat cancer including surgery, radiotherapy, and anticancer drugs. A combination of treatments is often used to give the best control. Referral to a specialist centre for treatment may be necessary for more advanced tumours.

Is surgery always necessary?

Surgery remains the best way to treat most tumours and in many cases can be curative. In most instances the goal of surgery is to remove all of the tumour cells present in a given location, thereby curing the patient or at the least relieving symptoms for an extended period of time. Success depends on many factors, including size and location of the tumour, specific tumour type, and type and extent of the surgical procedure. The last factor is influenced by the experience of the surgeon and referral may be necessary. Some cancers are too large or are in locations where they cannot be removed completely by surgery alone. In these cases surgery may be used to remove as much of the cancer as possible, while minimising damage to surrounding normal tissues and vital structures. Because cancer cells will have been left behind, some additional form of cancer treatment is used following debulking surgery, such as radiation or anti-cancer drugs.

If my pet has radiotherapy will all of its hair fall out?

In the majority of dogs the only side effect will be a small area of hair loss at the tumour site; nausea, vomiting, diarrhoea and other unpleasant side effects commonly reported in people are not a problem in animals. Radiotherapy uses high energy x-rays to kill the cancerous cells. The radiotherapy is given as a course of treatments over a few weeks. Many tumours that are not operable can be treated by radiotherapy including those affecting the mouth, nose, other head and neck sites, skin and brain. Cures are achieved in certain cases and a considerable number of tumours shrink to a very small size and only regrowing after many months of good quality of life.

Will my pet be very ill if it has anti-cancer drug treatment?

Certain types of cancer can be controlled well by anti-cancer drugs, in particular tumours of the lymph glands (lymphoma or lymphosarcoma), leukaemia and some cancers with a high likelihood of spread. This is a form of chemotherapy however serious side effects are infrequent in animals following anti-cancer treatment. Unfortunately anti-cancer drugs rarely cure animal tumours but for certain cancers they can produce remissions with excellent quality of life for the patient.

Is cancer treatment for pets worth doing?

As in humans, tumours are more common in older pets but with due care there is often no reason why they should not be treated. Many pets if it were not for their tumour, would be otherwise healthy individuals. Surgery, and to a lesser extent radiotherapy, can often be curative. Drug treatment and radiotherapy can often achieve good periods of remission with return to excellent quality of life. For a 10 year old dog, an extra 12 months is an extra 10% of its life. Which ever treatment is used the paramount consideration is always quality of life.