The CancerWeb Report, What's New In Cancer: July, 1996
Prostate Cancer

• Sexual dysfunction, the most distressing aspect of prostate cancer - A survey of 431 men aged between 50 and 80 years with prostate cancer, and 435 randomly chosen age-matched controls, was carried out by researchers at the Karolinska Institute and Hospital in Stockholm, Sweden. The found that although most men reported an age-related falling-off in sexual desires/thoughts, capacity for erection, orgasmic pleasure, and ejaculate volume, these complaints were significantly more common among the cancer patients (75-90%) than among the normals (51-78%). Over twice the proportion of prostate cancer patients than normals reported severe distress over these symptoms. Interestingly, urinary and bowel complications - urgency, urinary leakage, or weak urinary stream - were of much less concern, and only 1-3% reported severe distress from these problems. (Helgason, Br J Cancer 73:1417, 1996)

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• A new experimental model for studies of human prostate cancer? - There is a shortage of tumor models that mimic the behavior of human prostate cancer, which typically responds well to androgen deprivation, but then relapses within months to years. Experimental animal tumors and xenografts, that is human tumors growing in mice, show poor response to androgen deprivation, but an article in the July 1, 1996 issue of Cancer Research, describes a xenograft (called CWR22) that behaves very much like the tumors growing in prostate cancer patients. It regresses after androgen deprivation (in his case castration), with a 3,000-fold drop in blood PSA values, that subsequently return to normal. Tumor relapses in some animals, and there is an overall 3-4-fold increase in survival. This model may be very useful in developing new treatment approaches. (Nagabhushan, Cancer Res 56:3042, 1996)

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• Is PSA a good indicator of response to therapy? - Reliance on PSA measurements, originally a diagnostic indicator, as a surrogate for response of prostate cancer to therapy is now widespread, but is it always justified? A preclinical study involving treatment with the drug suramin of mice with two different strains of prostate cancer, one dependent on androgens and the other non- responsive to androgens, sounds a note of caution. Researchers from the M.D. Anderson Cancer Center in Houston found that suramin only inhibited the growth of the androgen-dependent tumor despite the fact that it decreased the expression of the PSA gene and serum PSA levels in animals bearing both tumor lines. PSA levels should be interpreted cautiously in studies of drug therapy that does not affect androgen-dependent disease. (Thalmann, J Natl Cancer Inst 88:794, 1996)

  Editor's Comment: - As a footnote to this report, results presented at the ASCO Meeting, and discussed in the "News" section of the same June 19, 1996 issue of the Journal of the National Cancer Institute (page 791), give some idea of how low PSA levels should fall in treated patients to give some prognostic implications. Whereas 10 years after PSA had fallen to 0.5 ng/mL or less, 84% were still disease-free, only 29% of those whose lowest levels were 0.5 ng/mL and above were disease-free at 5- years, and tumor recurred in all whose levels never fell below 1 ng/mL.