Cancer in primary care
Screening case histories
Dr William Hamilton provides two case studies which illustrate the implications of screening test results in discussing cancer risk and treatment options with the patient
Tracy – moderate dyskaryosis
Tracy is single, 28, and a receptionist at the local dental surgery. She doesn't come to the surgery much, other than for smears and for travel advice for her exotic foreign holidays. Her smear report says 'moderate dyskaryosis – referral recommended'.
What do you do?
GPs have three main functions in cervical screening . First, to organise both the taking of the smears and a watertight system of dealing with results. Second, to discuss their results with women, and, third, to ensure referral when required.
You will want to discuss with Tracy the natural history of abnormal smears and the (uncomfortable) fact that she has quite advanced changes, for which treatment is recommended. The risk for Tracy of progression to cancer is probably higher than 1% a year. You will also want to make the referral for colposcopy and ensure it is prioritised.
Ivor – a raised PSA
Ivor is a manager in one of the local factories and is aged 53. He has executive screening as one of the benefits of his job. He has come to see you because the doctor at the screening medical found his PSA to be 4.7ng/ml.
The doctor has posted Ivor a printout of the results and recommended he see you for further investigation. He has no symptoms.
•What is the chance that Ivor has prostate cancer?•Should he have a transrectal ultrasound and biopsy? If so, will it hurt?•What happens if he does nothing?
With a PSA over 4ng/ml, the risk is somewhere between 24% and 38%, depending on which screening study you read. These risks are, of course, quite high but the real question is this: what is the risk of clinically significant cancer that poses a threat to life?
No study has ever been able to put an accurate figure to that question but it is clearly less. Although you will make a referral, a rectal examination is appropriate, as you may be able to palpate an enlarged prostate or perhaps a nodule.Most urologists would recommend a transrectal ultrasound and biopsy. It may be painful (though it may not) and patients may experience rectal bleeding afterwards. Several biopsies will be taken, as a cancer may be missed in a single core (or indeed in several cores). If a cancer is found, one treatment option is watchful waiting, though this is less popular than it was. While the current evidence is not definitive, there may be small reductions in mortality when treated surgically. Ivor is young and the urologist is likely to recommend surgery or one of the newer treatments such as brachytherapy or high-frequency ultrasound. Even if the benefits of surgery prove to be real, the numbers needed to treat (NNTs) in the surgical trials were quite large, so doing nothing at the treatment stage is a reasonable option and, by extension, doing nothing at the diagnostic stage would be reasonable too. If such an option were chosen, regular PSAs would be wise.Dr William Hamilton is a GP and senior research fellow, academic unit of primary health care, University of Bristol