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Note from Dr Stuttaford: As with all the questions we answer, we have to deal with the underlying principles that the question highlights rather than a special case. We don't know the details of any correspondent's medical history, nor can we examine them. Only a patient's own GP, oncologist or urologist would be in a position to explain the treatment recommended that may well, quite rightly, be different from the usual practice.

I developed prostate cancer in 1998 (age 61) and was treated with radiotherapy the same year. My PSA reading dropped immediately to less than 1.0 and remained at that level until 2003, when it began a slow rise (with occasional reversals) to 9.0 in November 2006. My consultant has been monitoring my PSA with a view to an eventual commencement of hormonal treatment. I have not been told what level of PSA will trigger the hormone medication, and I am concerned by recent media reports of cancer treatments being started too early, simply to let NHS people tick the 'treatment in progress' box. What is the PSA number that, in your opinion, would represent the optimum level at which medication could commence? Michael Hewitt, Ousden, Suffolk

You and I had our prostate cancers diagnosed at much the same time and so I read your letter with great interest. The good news is that your PSA dropped so rapidly after the radiotherapy. It never returns to its lowest point immediately, but the faster it does the better the outlook, and the more likely that the initial tumour has been well zapped.

As in your case my PSA, after a radical prostatectomy rather than radiotherapy, began to climb after about five or six years. My consultant and I belonged to the school of thought that believes that the PSA should preferably be treated with hormones once it has reached one or two, after starting, in my case, at less than 0.05. For me, this corresponded with an increase in the speed at which the PSA had begun to rise. Any acceleration in the rate of rise in the PSA is always an important factor in determining treatment. Patients who have radiotherapy as their initial treatment will rarely have such a low PSA after therapy as those who have an apparently successful radical.

I don't think you need be concerned that GPs and oncologists will start hormone therapy early just so that they can tick the box for treatment in progress. The other side of this is that by not having hormone treatment early the NHS is saving several thousand pounds a year. In my opinion, the advantage of early treatment is that there does seem to be some, possibly debatable, evidence that starting treatment sooner rather than later may give the patient a slightly longer period of remission.

The disadvantage is that a patient has to put up with the side effects of the hormones for a longer time. As in every branch of medicine there is always a balance between the advantages and disadvantages, and where this balance is set is a matter for discussion between the doctor and the patient. I was impressed by the thought that starting hormones with a PSA of between 1 and 2 has in some studies been shown to give a fractionally longer period of remission. Many of my patients have taken the other view and decided to have a longer period without the inconveniences brought on by hormone therapy.

My prostrate cancer was diagnosed in 1997 after a biopsy. Radiotherapy treatment followed. My PSA readings fluctuate summer and winter, but have now recently increased to 2.4/2.5. Is this fluctuation unusual and does the increase indicate that the cancer may be returning? Roger Gillham, Windsor

After radiotherapy, especially with the doses given in 1997, it is unusual for the PSA level to reach levels of less than 0.05 per cent. That a PSA reading has remained constant between around 2.4 and 2.5 for ten years is an excellent result. If your PSA is beginning to show a steady increase, (this wasn't absolutely clear from your question), it is a matter that needs to be discussed with a patient's oncologist. Doctors are usually alerted to a possible change in their patient's condition if they have three or more PSA results that have risen when tested at agreed intervals. Always remember that there are other factors that might have caused an increase but never take a chance.

I am 58 and subject to a "watch and wait" regime of quarterly PSA tests, having been diagnosed with prostate cancer (mid-range gleason score) some 18 months ago. My PSA reading was eight at the time of biopsy and diagnosis, then declined to five over the course of the following year but has now risen to nine. I find this graph somewhat puzzling! As a result of the recent increase, I am to undergo a bone scan and pelvic MRI before a further meeting with my consultant in July. If the scans reveal anything untoward, I imagine that some sort of treatment will be recommended. However, what if the scans are "clean", so we can be fairly confident that the cancer has not spread? I believe I am right in saying that I am comparatively young to have prostate cancer. Is this an important factor in deciding whether, when and how to start intervening? I was successfully operated on for colon cancer in 2002 and am currently in the clear on that front. Name withheld, Cambridge

The regime that you describe is not now known as watchful waiting, but by any other term that implies that the doctor's have, as in this case, kept a very close eye on what is happening. When a PSA shows a regular and persistent rise it is important that the cause for it should be discovered, hence the reasons for bone scans, MRI etc. It is never possible to be certain that any patient, whatever their PSA, hasn't micrometastases elsewhere in the body. These are small groups of aberrant cells that have spread from the initial cancer, possibly before treatment started, remain dormant but have the potential to coalesce into a tumour if they become activated. If a secondary is found other treatment will be instituted.

The age at which men are developing prostate cancer is falling. Most of these cancers still start in the sixties and beyond but all urologists are seeing the occasional patient in their forties and many more in their fifties. Last year I met a man who had developed cancer of the prostate at the age of 36, but that is very unusual.