Keeping tabs on prostrate cancer
Prostate cancer is very common among West European and North American men (slightly less so among Jews and Orietals). The risks increase with advancing years, especially after age 50. Prostate cancer currently affects eight per cent of Canadian men, somewhat behind breast cancer in women. Despite the rising incidence, the good news is that this cancer usuaally grows very slowly and, as one eminent clinician puts it, “many more men die with prostate cancer than of it.” Autopsy studies reveal that latent or unsuspected prostate cancer (producing no symptoms or detrimental health effects) exists at death in about 50 per cent of men over 70 years old and 40 per cent of men over age 60. Risks of prostate cancer increase for those with close male relatives who had the disease — double if one close family member had it and 10 times higher if two relatives suffered from it.
No symptoms in its early stages
The prostate gland is a small, chestnut-sized organ of rubbery consistency that becomes harder if cancer is present. (SEE DIAGRAM) Prostate cancer varies greatly in malignant aggressivity, rarely producing symptoms in its early stages. It is usually found only when men see a physician for some other problem and a rectal exam detects a nodule in the prostate. Even if alerting symptoms do appear, they resemble those of benign/harmless prostate enlargement: urination difficulties or perhaps blood in the urine. By the time it is found, prostate cancer has often spread to the lymph nodes, bones or other areas and bone pain, typically in the back or legs, may be its first alerting sign. But prostate cancer produces symptoms only in about a third of those who have it, often remaining dormant, needing no therapy other than regular observation. For example, early prostate cancer in a 78 year old man with an estimated eight year or so life-expectancy may not warrant the risks of surgical removal. But a similar cancer found in a younger man, say at age 65, would likely be removed to prolong survival. Large prostate cancers many not merit prostate removal, since the disease has probably already invaded other sites.
Early detection tests not very reliable
Experts debate the usefulness of screening tests because none of the detectin methods are trustworthy. And even if found early, clinicians don’t always know the best treatment to suggest as many prostate tumours grwoo too slowly to pose a threat.
The detection methods include:
* Digital rectal examination (DRE), the oldest, easiest, quickest and simplest prostate cancer test, is painless and takes only a minute to do. Although it remains the primary detection tool, DREmisses about a third to a half of prostate cancers beyond the finger’s reach, also relying to some extent on the examiner’s experience. Only about one third of suspicious prostate nodules or thickenings prove to be cancerous on biopsy, giving a high “false positive” rate. One Swedish study showed that although prostate cancer was suspected in 45 of 1,163 men aged 50-69, it was confirmed only in 13. The danger of risky investigative procedures following a “false positive” result must be weighed against the possible advantages of prompt treatment.
* Ultrasound prostate exams may be done abdominally, via the urethra, or more commonly by t ransrectal ultrasound examination (TRUS) with a small transducer probe. Improved ultrasound methods can now detect some small tumours not felt digitally, but TRUS picks up only about 75 per cent of cases, still missing a quarter of the cancers felt by rectal exam. The Canadian Task Force considers ultrasound too unreliable and both false positive and false negative results too frequent for its inclusion as a routine prostate cancer test in healthy, symptom-free men. However, TRUS is useful in checking for cancer recurrence after prostate removal.
* Blood tests for prostate-specific tumours markes include the older, less sensitive one for prostatic acid phosphatase (PAP) and the more accurate prostate specific antigen or PSA test developed in 1979. However, as PSA levels may be elevated even with a non-cancerous, enlarged prostate, most experts consider ths marker too inaccurate for routine screening in symptom-free men. But combined with other tests, PSA levels do help to establish the presence of prostate cancer, being particularly useful for monitoring patients for recurrence after treatment.
* Combined screening tests, using all three methods, are more efficient than any one test alone. If only the rectal exam is positive, ther’s a 30-50 per cent chance of prostate cancer being reprsent but if both DRE and PSA results are positive, there’s a 70 per cent chance of prostate cancer. If all three tests — rectal exam, blood PSA and ultrasound — are abnormal, some studies show a 90 per cent accuracy rate. Therefore several health agencies, including the American Cancer Society, suggest sequential screening — routinely doig DRE and blood PSA tests, which are quick, easy and cheap, followed by ultrasound if either test is abnormal. If all three tests are possitive a biospy would follow. This approach is still being evaluated, “but,” says one University of Toronto expert, “many urologists believe in screening men over age 50 who come to their office using rectal and PSA tests, followed by ultrasound if either of these two is possitive.” Even if the ultrasound exam shows nothing (as happens in 20 per cent those with prostate cancer) but the PSA is elevated, some urologist suggest a biopsy.
* Biopsy — the “goal standard” test — takes a core of cells from the suspicious area via the rectum or urethra and is essential to confirm the presence of prostate cancer. It can be done with one of several newly available techniques such as fine needle aspiration, a spring-driven biopsy gun or transrectally (removing tissue through the rectum), a painless office procedure done without anesthetic. The new prostate biopsy techniques are usually done under antibiotic cover to prevent infection.
Treatment choices for prostate cancer
The treatments for prostate cancer are almost as vehemently argued as its detection. There is no single, safe, ideal treatment for prostate cancer. Complete, surgical prostate removal or radiation therapy, sometimes aided by anti-hormonal agents, are the main options. no treatment but a “watch and wait” approach is usually suggested for elderly men with small tumours and a life-expectancy under 10 yearsM, in whom early prostate cancers can usually be left alone. Younger men with cancer confined to the prostate gland may be given a choice of: no treatment (just observation), surgical removal, radiation (usually daily, on an out-patient basis, for five to six weeks) or combination therapy using anti-hormonal agents. Most authorities agree with the U.S. National Institute of health that “radical prostatectomy (complete prostate removal) and radiation are the most effective forms of treatment for tumours limited to the prostate.” Provided the cancer has not yet invaded other areas, removing the prostate is the usual strategy for those who are not too old, too sick or too frail to tolerate surgery. However, the best treatment remains controversial, as prostate surgery carries some risks and removal doesn’t guarantee a cure for tumous that have metastasized (spread). While only some prostate cancers will progress, it’s impossible to tell which and the deciision to remove the prsotate for cancers that may not expand is colured by the knowledge of post-surgical consequences which include: urination difficulties, incontinence and sexaul impotence. However, improved operating techniques now manage to avoid post-operative impotence by saving the nerve that controls potency in about 60 per cent of cases (compared to 100 per cent impotence after the older operations).
Hormone treatments for prostate cancer that has spread formerly involved high does of female hormones (estrogens) to lower testosterone to castration levels, a strategy largely going out of fashion because of feminizing effects and cardiovascular complications.
Ney synthetic anti-androgens are now available with less drastic side effects, including:
* LH-RH analogues (that mimic the brain hormone which triggers testosterone release), such as gosereline (Zoladex) now given as monthly injections. LHRH analogues have few side effects other than a slightly diminished sex drive. But while LHRH-imitators can lower testosterone levels they only control tumour expansion in androgen-dependent cancers that rely on the male hormone for growth.
* Non-steroidal anti-androgens, some of which don’t terminate potency, are bieng tried with varying success, including ketoconazole (an anti-metabolite) and flutamide to block the tumour-stimulating influence of male hormones.
Therapies that offer promise but have yet to be evaluated include: laser and light therapy, high energy shock-wave treatment and microwave coagulation (still purely experimental).
COPYRIGHT 1991 Strategic Inc. Communications Ltd.
COPYRIGHT 2004 Gale Group