Update: 25.07.2008
New drug shows promise against aggressive prostate cancer in small trial
British researchers believe a new drug could treat up to 80 per cent of patients with an aggressive and previously drug-resistant form of prostate cancer.
A phase I clinical trial by the Institute of Cancer Research and the Royal Marsden Hospital found that the drug abiraterone caused tumours to shrink and levels of prostate specific antigen (PSA) - a protein associated with prostate cancer activity - to drop in the majority of the 21 patients who received the drug.
The results suggest the drug could benefit up to 10,000 British men each year who are diagnosed with aggressive prostate cancer.
Dr Sally Burtles, director of drug development for Cancer Research UK, said: "We are delighted that this drug, originally developed by us, is continuing to show promise and has the potential to make a real difference to men with an aggressive form of prostate cancer."
The drug works by blocking the production of key hormones involved in driving prostate cancer growth, both in the testes and in the tumour itself.
This is particularly important in aggressive forms of prostate cancer, in which the tumour tissue is believed to produce its own supply of hormones for tumour growth and therefore cannot be treated with existing drugs that only block hormone production by the testes.
According to lead researcher Dr Johann de Bono, "The Royal Marsden patients in this study have been monitored for up to two-and-a-half years and with continued use of abiraterone they were able to control their disease with few side-effects." The researcher also noted that some patients were able to stop taking morphine for the relief of bone pain.
"These men have very aggressive prostate cancer which is exceptionally difficult to treat and almost always proves to be fatal," he continued.
"We hope that abiraterone will eventually offer them real hope of an effective way of managing their condition and prolonging their lives."
The results of the phase I clinical trial, which involved 21 men with prostate cancer that had already proven resistant to several hormone therapies, are published in the Journal of Clinical Oncology.
Cancer Research UK's prostate cancer expert, Professor Malcolm Mason, who is based at Cardiff University School of Medicine, said: "These early results are extremely exciting but there's a lot more work needed to establish what abiraterone's place will be in treating men with prostate cancer.
"At the moment the studies are being done on a small number of men with very advanced disease so it's much too early to say what role the drug might have in treating others with earlier stage prostate cancer. We need the results of a much larger study to see if this early promise will be fulfilled."
Update: 22.07.2008
Drug for deadly prostate cancer
Scientists are hailing a new drug to treat aggressive prostate cancer as potentially the most significant advance in the field for 70 years.
Abiraterone could potentially treat up to 80% of patients with a deadly form of the disease resistant to currently available chemotherapy, they say.
The drug works by blocking the hormones which fuel the cancer.
The Institute of Cancer Research hopes a simple pill form will be available in two to three years.
An advanced clinical trial involving 1,200 patients around the world is currently under way, with more trials likely later this year.
Prostate cancer is the most common cancer among men.
It is estimated that up to 10,000 men a year in the UK are diagnosed with the most aggressive - and almost always lethal - form of prostate cancer.
Typical life expectancy following chemotherapy is no more than 18 months.
It had been assumed that the cancer was driven by sex hormones such as testosterone produced in the testicles.
Current treatments work by stopping the testicles from producing testosterone.
New action
However, experts have now discovered that the cancer can feed on sex hormones from all sources, including supplies of the hormone produced by the tumour itself.
Abiraterone works by blocking production of the hormones throughout the body.
The latest study, published in the Journal of Clinical Oncology, is based on just 21 patients with advanced, aggressive prostate cancer treated with the drug - but data has been collected on a total of 250 worldwide.
It found significant tumour shrinkage, and a drop in tell-tale levels of a key protein produced by the cancer called prostate specific antigen in the majority of patients.
Many of the patients have reported a significant improvement in the quality of their lives.
Some were able to stop taking morphine for the relief of pain caused by the spread of the disease to their bones.
Real hope
Lead researcher Dr Johann de Bono said the findings needed to be confirmed in larger trials.
At this stage, no patient has taken the drug for longer than two-and-a-half years, and so it has not been possible to determine exactly what the effect of the drug on life expectancy will be.
But he said: "We believe we have made a major step forward in the treatment of end-stage prostate cancer patients.
"These men have very aggressive prostate cancer which is exceptionally difficult to treat and almost always proves to be fatal.
"We hope that abiraterone will eventually offer them real hope of an effective way of managing their condition and prolonging their lives."
It is hoped the drug will also aid other cancer patients, including those with breast cancer.
Professor David Webb, an expert in clinical pharmacology at the University of Edinburgh, said: "This agent clearly looks promising, but it is still at the early stages of clinical development.
"It will be crucial to look carefully at the balance between its benefits and harms, before drawing firm conclusions about the usefulness of this new drug.
"Important side effects often only emerge with the larger clinical studies that now need to be done."
John Neate, of The Prostate Cancer Charity, said: "This is an exciting development which has been eagerly anticipated."
Cancer of the prostate gland, a walnut-sized organ surrounding the urethra in males, is the most common cancer in North American males. About 180,000 new cases of prostate cancer in the United States and 16,900 in Canada are diagnosed every year. For unknown reasons, the prevalence in black men is nearly twice as high as in white men. Prostate cancer risk increases with age, and some evidence suggests that high-fat diets may increase the risk of developing the disease.
Most prostate cancers are adenocarcinomas, cancers that arise in glandular cells of the prostate’s epithelial tissue. Prostate cancers usually progress slowly and produce no symptoms in the initial stages. Eventually, the tumor may enlarge the prostate gland, pressing on the urethra and causing painful or frequent urination and blood in the urine or semen. Sometimes pain in the lower back, pelvis, or upper thighs may signal that prostate cancer cells have spread to the ribs, pelvis, and other bones. All these symptoms, however, may have other causes, such as infection of the prostate or prostate enlargement, a natural result of the aging process.
The prognosis for prostate cancer is quite good if it is caught and treated early. The five-year survival rate for American men with prostate cancer is almost 92 percent, but this number rises to almost 100 percent if the tumor is caught early.
Prostate Cancer, malignancy of the prostate gland, a walnut-sized organ located under the bladder in males. The prostate gland surrounds the urethra, which is the tube that carries urine from the bladder to the penis. The American Cancer Society estimates that about 180,000 new cases of prostate cancer are diagnosed annually in the United States and that about 32,000 men die from the disease each year. According to the Canadian Cancer Society, each year prostate cancer is diagnosed in about 16,900 men in Canada and about 4,200 die from the disease. Prostate cancer is the second leading cause of cancer death, after lung cancer, in men living in the United States and Canada.
RISK FACTORS
The specific mechanisms that lead to the development of prostate cancer are still unknown, but several risk factors for the disease have been identified. Incidence increases with age—prostate cancer seldom develops before the age of 40 and is chiefly a disease found in men over the age of 65. It is most common in North America and in northwestern Europe but rare in South America, the Near East, and Africa. In the United States, black males, who suffer from the disease 37 percent more often than white males, have the world’s highest incidence. A growing body of evidence links diets rich in animal fats with prostate cancer. Dietary differences are believed to explain why the incidence of prostate cancer is 120 times greater in the United States than in China, where fatty foods are not part of the general diet.
Some foods seem to act as a shield against this disease. Studies show that tomato-based products protect against prostate cancer, possibly because tomatoes are rich in a substance called lycopene. Lycopene is an antioxidant, a chemical agent that inhibits or retards the cellular process of oxidation. Too much cellular oxidation can be dangerous to a person’s health because it produces molecules called free radicals that increase the risk of cancer developing in body tissues. Long-term, moderate doses of vitamin E, another type of antioxidant, may block the progress of prostate tumors.
Environmental factors, such as workplace exposures to cadmium, have also been associated with increased risk of prostate cancer. Family history plays another important role. Men whose fathers or brothers develop prostate cancer are more likely to develop the disease. Researchers are beginning to identify genetic markers of prostate cancer. For instance, the gene known as hereditary prostate cancer 1 (HPC1) appears to significantly predispose men to prostate cancer when inherited in a mutated form.
SYMPTOMS AND DIAGNOSIS
Prostate cancer usually progresses slowly and produces no symptoms in its initial stages. Warning signs may eventually include difficult or painful urination; frequent urination, especially at night; and blood in the urine or semen. Pain in the lower back, pelvis, or upper thighs may signal that prostate cancer cells have spread to the ribs, pelvis, and other bones. All these symptoms, however, may have other causes, such as infection and prostate enlargement, which are a natural result of the aging process.
Many doctors perform screening tests for prostate cancer during regular physical exams in order to identify the disease in its earliest—and most curable—stages. Doctors perform a digital rectal examination, in which the physician uses a gloved finger to gently check the smoothness of the rectal lining. If cancer is present, a physician may feel a nodule or other prostate irregularity. Another screening test, called the prostate-specific antigen (PSA) test, measures levels of a protein called prostate-specific antigen in the blood. Prostate cancer cells overproduce this protein, causing an elevation of PSA levels in blood. If screening tests indicate cancer is present, a physician will usually perform a biopsy, in which a tissue sample is removed from the prostate and examined under a microscope. The American Cancer Society recommends that men aged 50 years and older should have an annual digital rectal exam and PSA test. Men who have a high risk for the disease (blacks or those with a family history of prostate cancer) should talk to their doctors about starting annual screening tests at a younger age.
The prostate gland is a walnut-sized organ that rings the male urethra. The secretions of the prostate and Cowper’s glands add nutrients to semen, the fluid in which sperm is ejaculated from the body. Cancer of the prostate gland is a common type of cancer in men.
TREATMENT
Localized cancers may be treated with hormones and anticancer drugs, which shrink the prostate tumor and suppress its ability to metastasize (spread to surrounding tissue). Certain drugs can slow the cancer’s growth after it has spread beyond the prostate.
In many cases, a prostatectomy—the surgical removal of the prostate—is performed, often in conjunction with radiation. However, this surgery can cause impotence and urinary incontinence. An alternative is brachytherapy, or seed implant therapy, in which radioactive iodine “seeds” are inserted into the prostate. The procedure, performed under local anesthesia, spares healthy, nearby tissue and appears to be as effective as surgery for men with early stage prostate cancer.
In men over the age of 70, the disease often progresses so slowly that death results from other causes before symptoms of prostate cancer have time to emerge. For this reason, some physicians believe that many patients in this age group can forego surgery and other treatments as long as their condition is regularly monitored—a treatment known as watchful waiting.
Several potential treatments are under investigation, including cryosurgery, in which freezing temperatures destroy cancer cells, and gene therapy, which bolsters immune-system defenses against cancer.
PROGNOSIS
According to the American Cancer Society, 92 percent of men diagnosed with prostate cancer survive at least five years after diagnosis, and 67 percent survive ten years. If the cancer is discovered while still localized, the five-year relative survival rate is nearly 100 percent. About 79 percent of prostate cancers are discovered at this stage.
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