MEDICAL MATTERS:Lack of certainty leads to anxiety for patients, writes MUIRIS HOUSTON
DESPITE THE many advances of modern medicine, it remains surprisingly common for doctors to be unable to offer a definitive diagnosis to a patient.
Even after fairly extensive investigation, the cause of a collection of symptoms can remain elusive. For example, we use the term pyrexia of unknown origin (PUO) when someone has a persistent elevated temperature for which the initial series of investigations draws a blank.
Medicine has strategies for dealing with these situations, but for the patient it is most unsatisfactory and can be frankly worrying. Without a named disease, there may be a feeling of not being taken seriously. For the doctors looking after that person, the lack of definition may lead to them feeling professionally inadequate.
In the US, the National Institutes of Health (NIH) has set up the Undiagnosed Disease Program for patients who are seriously unwell. Success for the programme comes when doctors are able to identify a known disease that has eluded diagnosis.
Their success rate remains frustratingly low, but even patients who are told they have a named incurable condition are perversely grateful. For families in particular, there is a relief in a condition being given a diagnostic label, even when no cure is available.
In cancer care, 3-5 per cent of malignancies are classified as cancer of unknown origin (CUO). It occurs when a secondary cancer, known as a metastasis, is identified but despite a thorough medical history, physical examination and standard investigations, the primary tumour cannot be found.
The natural progression of cancer of unknown origin is quite different to cancers where the primary site is known. However, CUOs tend to spread unusually rapidly; they are also unpredictable in their pattern of spread and are often quite aggressive tumours.
Assuming the usual blood tests, X-rays and even scans have been carried out on the patient with cancer of unknown primary with no positive results, what happens next?
CAT scans have been shown to help in about 40 per cent of CUOs and can also guide doctors when trying to biopsy a suspicious area in the body. MRI scans are helpful in women suspected of having primary breast cancer. And PET (positron emission tomography) scans are good at picking up hidden lung cancers and head and neck cancers.
PET’s ability to track active processes such as blood flow and metabolism enables it to assess the body’s functioning at any given time. PET is based on the principle that most disease states cause increased cellular activity, making it ideal for finding cancer cells.
Another widely used technique is that of immunohistochemistry, the science of identifying known tumour markers in tissue biopsies. Among the 10 or so markers tested for is prostate specific antigen (PSA) in men who have bone secondaries but in whom it has been difficult to locate a primary tumour in the prostate. The ovarian cancer marker CA125 is a useful option in women with secondary cancer growth in the abdomen.
Doctors may also deploy scopes in an effort to find the cancer. Bronchoscopy may pick up evidence of lung cancer, while a gastroscopy may reveal a hidden stomach cancer.
However, a combination of diagnostic imaging, immunohistochemistry and endoscopy may identify just three in every 10 hidden primary cancers. There is hope that genetic profiling may increase the detection rate to 80 per cent.
But it’s not all doom and gloom: young men with secondary growths in lymph nodes between the lungs respond well to treatment.
How do you treat these CUOs? Usually there is a well-founded suspicion of where the primary is and so the chemotherapy regime for that cancer is started. For those truly mysterious tumours, cancer specialists will often try a combination of two chemotherapy drugs while assessing the patient’s response.
Having an undiagnosed condition is a challenge. When that disease is a cancer with a hidden primary, one could be forgiven for thinking the gods really were against you.