August - December 2005 Issue
Drug Therapies Can Help Prostate Cancer Patients Survive Longer
Nancy B. Davis, MDMedical College of Wisconsin Medical Oncologist
Medical oncology is the branch of cancer care that treats tumors with chemotherapy and other drugs. It offers life-extending options for patients with prostate cancer.
Q. For prostate cancer, when does medical oncology enter the picture?Medical oncology for prostate cancer starts with hormone therapy. This therapy is standard for men who have relapsed after surgery or radiation therapy or those who have metastatic prostate cancer (cancer that has spread to other parts of the body). Hormone therapy involves injections of a hormone drug that turns off testosterone production. The drug actually starves the cancer cells, because testosterone is what feeds prostate cancer. The injections are usually given three to four times a year, but now a yearly implant is available for some patients.
Q. What are the side effects of hormone therapy?In general, side effects can include hot flashes, weight gain, breast growth and tenderness, loss of libido and impotence.
Q. How effective is this therapy?It is exceedingly effective in that more than 98% of men respond to hormone therapy initially. It does not cure prostate cancer but it's effective at inducing remission.
Typically, what we see is that the Prostate-Specific Antigen (PSA) decreases and/or symptoms of metastatic disease improve with hormone therapy. Eventually, nearly all men develop resistance to hormone therapy.
Although PSA screening is recommended because early stage prostate cancer is curable with surgery or radiation, metastatic prostate cancer is not considered a curable disease.
Q. What options are there after hormone therapy?Chemotherapy can improve survival in advanced prostate cancer. Chemotherapy is indicated for men whose cancer has stopped responding to hormone therapy and who have metastatic disease. After we exhaust the line of hormone therapies, chemotherapy — specifically, a drug called Taxotere — is indicated for men with cancer that is resistant to hormone therapy and shows evidence of metastesis.
Taxotere is a chemotherapy agent that blocks the growth and division of cancer cells and can induce remission. About 60% of men will respond to Taxotere. This means that the PSA will decrease, any bone pain or symptoms will improve, and, if they have measurable soft tissue disease, that will shrink as well. Taxotere has been shown in two large studies to improve survival in these patients when compared to older chemotherapy regimens or supportive care.
Q. How long does Taxotere therapy last?Usually Taxotere is given by vein once every three weeks for six cycles, or 18 weeks of chemotherapy. However, if a man is still responding after 18 weeks, we may push on for a few more cycles if it is being well tolerated.
Unfortunately, chemotherapy affects more than just cancer cells. All chemotherapies usually have side effects on other rapidly growing and dividing cells — like hair (so we get hair loss), the lining of the mouth (so we end up, sometimes, getting ulcerations inside the mouth) and blood cells (so we cause myelosuppression, which is a decrease in white blood cells, red blood cells and platelets).
Q. Are there any alternatives to Taxotere? Nothing has been proven to be better than Taxotere for first-line chemotherapy in hormone refractory prostate cancer. There are, however, many chemotherapy agents that are active in prostate cancer, and by active I mean they will decrease the PSA, they will improve your symptoms, and they will improve your quality of life — but they have not been shown to prolong life.
Q. What kind of prostate cancer research are you involved in?We have a trial open right now evaluating a second-line chemotherapy agent for men who have progressed or relapsed after Taxotere chemotherapy. This is a randomized study looking at the use of chemotherapy plus steroid hormones versus steroid hormones alone.
In addition, the department of urology has a vaccine study for men with intermediate-grade metastatic prostate cancer. This study involves attempting to use the patient’s own immune system to eradicate the prostate cancer. While there have been a number of vaccines targeting different markers of the prostate cancer cells, some have worked and some have only been very interesting for a while, without success in large studies. Hopefully, this particular vaccine will be one of the ones that are effective.
Finally, another study we have open is looking at intermittent versus continuous use of hormone therapy for men who have not previously been treated with hormones for metastatic prostate cancer. This study is pretty exciting because the standard therapy is continuous hormones every three to four months for life. This study is looking at whether we can give hormone therapy in intermittent bursts and then take a break, or drug holiday, from therapy. Potential benefits from an intermittent approach include relief from side effects and improved quality of life during drug holidays. But underlying this study is also the question: Can the usefulness of hormone therapy in metastatic prostate cancer be prolonged past an average of 2 years? In other words, is it possible to delay development of a hormone resistant state through intermittent exposure to hormone therapy until the cancer starts to re-grow, and then use it again, and then take another break?
Author: Nancy B. Davis, MD
Source: Every Day
Date: August - December 2005