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Prostate Cancer Explained

Posted Aug 24 2008 1:49pm
ROBERT DREICER, MD: Prostate cancer is, in the United States, a very common cancer. Other than skin cancer, it's the most common cancer in men. This year, it's estimated about 230,000 cases of prostate cancer will be diagnosed.

ANNOUNCER: Prostate cancer is also the second-leading cause of cancer death among men in the US. About 30,000 men die of the disease each year. The most significant risk factor is age.

PHILIP KANTOFF, MD: Probably more than any other cancer, prostate cancer is related to age. You rarely see prostate cancer in men under the age of 40. Maybe 10 percent of men who develop prostate cancer will do so in the range of 40 to 50 and the incidence of prostate cancer rapidly increases as a function of age after that.

ANNOUNCER: Other risk factors include diet and family history. Some combination of genetics and environmental factors lead to a high prevalence among African Americans.

WILLIAM OH, MD: Within the United States, the men at highest risk are African Americans. And, again, we're not certain to what extent this is contributed to by environmental factors or true genetic factors, but the bottom line is that we know, epidemiologically, that African-Americans have the highest rate of prostate cancer in the world and, therefore, we target our screening more aggressively towards African Americans.

ANNOUNCER: Screening used to be limited to a fairly primitive method called a digital rectal exam.

WILLIAM OH, MD: A digital rectal examination or DRE is when a urologist or an oncologist or a primary physician inserts a gloved finger into the rectum to feel where the prostate is. And this is the traditional way in which prostate cancers were detected before the advent of PSA screening. So if there's an abnormal prostate on examination, that's similar to finding a lump on the breast.

ANNOUNCER: PSA, short for prostate specific antigen, is a protein produced by prostate cells. Levels tend to rise with non-cancerous changes to the prostate that are normal with aging, a condition called benign prostatic hyperplasia, or BPH. However, a high or rising level can also indicate cancer. Doctors used to consider a PSA of 4 units a critical mark.

WILLIAM OH, MD: In general, this traditional cutoff for an elevated PSA was 4 or higher. However, we've become much more sophisticated over the last decade in understanding what the context is for a high PSA. So, for example, a level of 4 in a 50-year-old man would be considered abnormal, even though it's considered normal for the total range, and that's because men who are younger tend to have smaller prostates and therefore have a lower PSA at their baseline. Whereas, if you were 70 years old or 75 years old and had a history of having trouble urinating, BPH symptoms, a PSA of 4 could be perfectly within normal range.

ANNOUNCER: The PSA count is not a direct indicator of cancer, so it can not be the basis of diagnosis.

PHILIP KANTOFF, MD: Maybe a third of men with levels of PSA less than 10, which is the most common scenario, actually have prostate cancer. So the diagnosis of prostate cancer is not made on the basis of PSA, it's made on the basis of a biopsy of the gland.

WILLIAM OH, MD: Generally, the way the diagnosis is made is that an ultrasound's inserted into the rectum, which is adjacent to where the prostate is, and needles are placed by the urologist into the prostate. At least six biopsies are usually mandated, although now the standard has gone up to eight to ten biopsies taken. After the biopsies are removed from the body, they're sent to the laboratory and a pathologist reviews them.

ANNOUNCER: With PSA testing now very common in the United States, prostate cancer is usually caught very early. If it has spread, it probably has only done so at a level far below the resolution of imaging devices.

But doctors still want to know whether the disease is likely contained within the prostate, and how aggressive the disease may be.

PHILIP KANTOFF, MD: What is useful is taking a composite picture of the factors that characterize this cancer including: the clinical stage; the PSA; the Gleason score, or the grade of the cancer; and the percent of the biopsies that are positive; and also what has emerged over the last year or so, the rate change of the PSA over the previous year. How rapidly the PSA is going up. These five factors collectively will determine, to a large extent, the likelihood the cancer is all confined to the prostate, and therefore curable, or has escaped the prostate, and not curable with local therapy alone.

ANNOUNCER: One option for local therapy to cure early-stage prostate cancer is surgery, called a radical prostatectomy. Radiation therapy is another option, generally with a choice of techniques.

ROBERT DREICER, MD: One is external beam radiation therapy and what that simply means is using a machine that generates fine, controlled beams of X-rays and treats the body from the outside. The other major type of radiotherapy is brachytherapy or using radioactive seeds, which may be small little pellets, or wires that are placed directly into the prostate in a specific pattern to deliver high fields of radiation therapy.

ANNOUNCER: Yet another technique is called cryotherapy, which uses liquid nitrogen to kill prostate cells by freezing them. When doctors suspect prostate cancer is more advanced or more aggressive, therapies may be combined.

PHILIP KANTOFF, MD: For people on the higher end of the risk strata, having higher PSAs, have higher-grade cancers, more cores that are positive suggesting a higher volume of cancer, surgery might still be an option, but, generally, we begin to talk about multimodality therapy, combining hormonal therapy with external beam radiation, one form or another, or, conceivably, more aggressive experimental approaches.

ANNOUNCER: Sometimes prostate cancer reappears. The first sign is usually a return of PSA in the blood, or a rise from very low values. At that time, or later after careful monitoring, a patient may undergo what is known as hormonal- or androgen-deprivation therapy. This is to eliminate testosterone from the body, or to interfere with its use by the cancer.

Hormonal therapy involves either the surgical removal of the testicles, or the use of medications. Hormonal therapy is also used in treating men with prostate cancer who are first diagnosed with advanced disease, when the cancer has already spread beyond the prostate.

PHILIP KANTOFF, MD: The reason that this strategy is used is because the prostate cancer cell or tumor relies on the male hormone for existence and for growth. So if you deprive the cancer cell or the tumor of male hormone, you cause the cell generally to stop growing and in some cases can cause the cell to die and the tumor to regress.

ANNOUNCER: Hormonal therapy tends to fail after a period of time. But even then, further treatments are available. Recent research shows chemotherapy can increase life expectancy, and improve quality of life.

Some of the biggest advances in the treatment of prostate cancer may lie ahead, and may run parallel to the so-called "targeted" approaches being studied in other cancers.

ROBERT DREICER, MD: We are now evolving in oncology in general to a whole new area where therapies are more -- we like to use the word "biologically rational." It actually is targeting something we know about a specific cancer cell and a specific disease to try to disrupt function.

So what we're doing in prostate cancer is akin to what's being done in colon cancer and breast cancer. We're a little bit further behind in prostate cancer, because it's sometimes a little bit more difficult to study this disease, but we are beginning to make some progress.

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