The CancerWeb Report, What's New In Cancer: January, 1997
Prostate Cancer

• Another warning about excessive reliance on PSA measurements - An article by researchers at the Walter Reed Army Medical Center and the National Cancer Institute in Washington, DC, described a lack of correlation between the presence and absence of soft tissue metastatic disease seen and measured by CT scan, and PSA values determined at the same time. The patients enrolled in this study, reported in the journal Cancer Investigation, had a median age of 63 and were all unresponsive to hormone treatment. Among 177 prostate cancer patients, 19% had metastases equal to or larger than 2 cm in size, mostly in the lymph nodes but also in the liver. PSA measurements, however, did not differ between those with or without this soft-tissue metastatic disease. It is apparent that PSA values do not always reflect the true extent of disease. (Figg, Cancer Invest 14:513, 1996)

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• How best to identify p53 abnormalities in prostate cancer - Increasing attention is being paid to determining abnormal mutants of human chromosomes, such as the tumor-suppressing p53 in human cancers, as a possible guide to prognosis and treatment. Before reliance is placed on such genetic indicators however, we must be very sure of two things - the best way to identify these abnormalities, and of what exactly the alterations imply for the patient. An article in the January 1, 1997 issue of the Journal of the National Cancer Institute by the Cooperative Prostate Network in the US concluded that a combination of two measurements is necessary to identify all the possible p53 changes. Both tests are based on what is known as the polymerase chain reaction (PCR), but one starts from DNA (DNA-PCR-SSCP), while the other starts from RNA (ribonucleic acid) which is converted to its corresponding DNA before PCR is carried out (TR-PCR-SSCP). This is because many cancers contain more than one altered p53 gene. This situation may apply also to tumors other than prostate cancer. (Gumerlock, J Nat Cancer Inst 89:66, 1997)

  Editor's Comment: - p53 measurements more typically look at the protein product by immunologic methods rather than the specific mutations that may be present. It is interesting that a short report from a group of researchers in University College, Dublin, Ireland (Leahy, J Pathol 180:364, December, 1996) also concluded that measurement of overexpressed p53 protein was a better guide to identifying high-risk colorectal patients than was determination of specific mutations by PCR-SSCP, which showed no relationship to outcome.