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Xofigo for Advanced Prostate Cancer Approved by FDA

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Xofigo approved three months ahead of schedule under priority review program

The U.S. Food and Drug Administration today approved Xofigo (radium Ra 223 dichloride) to treat men with symptomatic late-stage (metastatic) castration-resistant prostate cancer that has spread to bones but not to other organs. It is intended for men whose cancer has spread after receiving medical or surgical therapy to lower testosterone.

Prostate cancer forms in a gland in the male reproductive system found below the bladder and in front of the rectum. The male sex hormone testosterone stimulates the prostate tumors to grow. According to the National Cancer Institute, an estimated 238,590 men will be diagnosed with prostate cancer and 29,720 will die from the disease in 2013. [Read more…]

Genistein in Soybeans May Halt Prostate Cancer Spread

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Genistein, an antioxidant found in soybeans, almost completely prevented the spread of human prostate cancer in mice, according to a study published in the journal Cancer Research. In the study, genistein was used in an amount equivalent to what a human being would consume in a soybean-rich diet.

Genistein decreased metastasis of prostate cancer to the lungs by 96% compared with mice that did not eat the compound, the first demonstration that genistein can stop prostate cancer metastasis in a living organism. "These impressive results give us hope that genistein might show some effect in preventing the spread of prostate cancer in patients," said the study’s senior investigator, Raymond C. Bergan, MD, director of experimental therapeutics for the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.

"Diet can affect cancer and it doesn’t do it by magic," Bergan said. "Certain chemicals have beneficial effects and now we have all the preclinical studies we need to suggest genistein might be a very promising chemopreventive drug."

Bergan has already shown in prostate cell cultures that genistein slows detachment of cancer cells from a primary prostate tumor, and checks cell invasion. It does this by blocking activation of p38 MAP kinases, molecules which regulate pathways that activate proteins that loosen cancer cells from their tight hold within a tumor, pushing them to migrate. "In culture, you can actually see that when genistein is introduced, cells flatten themselves in order to spread out and stick strongly to nearby cells," he said.

Researchers implanted groups of mice with an aggressive form of prostate cancer, having first fed them genistein. The amount of the chemical in the mouses’ blood was equivalent to human blood concentrations after eating soy foods, said Bergan. Genistein stopped lung mestasis almost completely, although it did not reduce the size of the tumors that developed within the prostate. Repeating the experiment produced he same result.

The size of tumor cells’ nuclei in the animals’ tissue was checked, to see whether he cells had flattened t in rder to spread. "Within a tumor, it is hard to tell where the borders of cells stop, so one way to measure adherence is to look at the size of the nuclei in cells and see if they are wider due to cell spread," Bergan said. "And that is what we found, demonstrating that the drug is having a primary effect on metastasis."

"What we think is happening here is that the cells we put in the mice normally like to move. When genistein restricted their ability to do so, they tried to compensate by producing more protein involved in migration. But genistein prevented those proteins from being activated," he said. "This is really a lesson for researchers who depend on biomarker studies to test whether a treatment is working. They need to be aware that those biomarkers might be telling only half of the story."

Source: Cancer Research, a journal of the American Association for Cancer Research. March 15, 2008.

Hormonal Components in Some Dietary Supplements May Promote Progression of Prostate Cancer

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A recent study by researchers at UT Southwestern Medical Center concludes that hormonal components in over-the-counter dietary supplements may actually accelerate the progression of prostate cancer, at the same time decreasing the effectiveness of anti-cancer drugs.

The study, published in the January 11, 2008 issue of Clinical Cancer Research, strongly advises patients to tell their doctor if they are taking any herbal or hormonal dietary supplements. It is also recommended that the use of such supplements is routinely documented as part of the patient’s health assessment.

"Physicians need to ask their patients not only about the prescription drugs they may be taking, but—perhaps even more importantly—about the over-the-counter drugs and supplements, which may have a profound impact on certain health conditions," said Dr. Claus Roehrborn, chairman of urology at UT Southwestern and one of the study’s authors.

The research commenced when two UT Southwestern patients developed aggressive prostate cancer mere months after starting daily use of the same dietary supplement—one for muscular development, the other for sexual enhancement. When Dr. Roehrborn and Dr.Shariat, a resident in urology and the study’s lead author, and their colleagues analyzed the product (not named in the study) they found that the label listed ingredients not present, misrepresented the concentrations of the ingredients that were present, and did not list all the steroid hormones in the product.

Hormone analysis showed the presence of testosterone and estradiol, a sex hormone. Testing of the product’s effect on human prostate cancer-cell lines revealed that the product was a more potent stimulator of cancer-cell growth than testosterone. Use of the anti-cancer drug bicalutamide, in increasing concentrations, proved ineffective.

"Bicalutamide is an oral nonsteroidal anti-androgen used to treat prostate cancer," Dr. Shariat said. "The fact that this supplement caused the drug to be less effective is very troubling." The researchers filed an adverse event report with the Food and Drug Administration, which in turn issued a warning letter to the manufacturer, who withdrew the product from the market.

"Unlike prescription and over-the-counter drugs, the law does not require nutritional supplements to undergo pre-market approval for safety and efficacy," Dr. Shariat said. "The current FDA regulatory system provides little oversight or assurances that dietary supplements will have predictable pharmacological effects or even that product labels provide accurate information for consumers."

It is estimated that 42% – 69% of U.S. adults use dietary supplements, at an estimated cost of $34 billion. People often use supplements in the belief that these natural products are safe and drug-free. The sale of androgenic steroids meanwhile is increasing exponentionally, with 2004 sales U.S. expenditures on testosterone supplements totalling an estimated $425 million.

"Given that testosterone supplements are in high demand, there is significant concern that supplements, in addition to the one we evaluated, may pose an urgent human health risk," Dr. Shariat said.

Researchers from Baylor College of Medicine in Houston also contributed to the research.

"The current FDA regulatory system provides little oversight or assurances that dietary supplements will have predictable pharmacological effects or even that product labels provide accurate information for consumers."

Prostate Cancer Mortality Rate Lower with Surgery Than Other Treatment Options

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Prostate cancer patients who opt for radiation treatment, hormone therapy, observation, or other forms of treatment for localized prostate cancer have a higher rate of death within 10 years than patients who have undergone surgery for prostate cancer, according to a recent Swiss study, published in the Archives of Internal Medicine.

As there have not yet been any notable randomized trials for prostate cancer treatments, treatment decisions are currently strongly influenced by the patient and physicians’ personal perferences and experiences, say the study’s authors.

Researchers used data from the Geneva Cancer Registry to assess all 844 patients diagnosed with localized (not yet spread) prostate cancer in Geneva between 1989 and 1998.

Of those men, 158 received prostatectomy, or surgery to remove all or part of the prostate; 205 had radiation treatment (radiotherapy); 378 chose watchful waiting, which entails active follow-up and treatment if the disease progresses; 72 underwent hormone therapy; and 31 had another type of therapy.

After 10 years, survival rates were 83 percent for those who underwent surgery to remove the prostate (prostatectomy), 75 percent for radiation therapy, 72 percent for watchful waiting, 41 percent for hormone therapy and 71 percent for other treatments.

"At 10 years, patients treated with radiotherapy or watchful waiting had a significantly increased risk of death from prostate cancer compared with patients who underwent prostatectomy," the authors wrote.

The increased mortality associated with radiotherapy and watchful waiting was primarily observed in patients under 70 years of age and in patients with poorly differentiated tumors, or tumors that have certain cellular characteristics and are more likely to spread aggressively.

While the authors recognize that their study can be improved through randomized clinical trials, they noted that "until clinical trials provide conclusive evidence, physicians and patients should be informed of these results and their limitations."

Source: Archives of Internal Medicine  2007;167(18):1944-1950.

GVAX Prostate Cancer Vaccine in Phase 3 Clinical Trials

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Doctors at a San Francisco Bay Area hospital are now in phase three clinical trials of GVAX, a prostate cancer vaccine developed by Cell Genesys, Inc. (CEGE)

While vaccines are commonly thought of as a preventive measure, they may also be used to treat an existing disease. Dr. Ari Baron, an oncologist from California Pacific Medical Center is leading the clinical trial on the GVAX prostate vaccine.

According to ABC news, Dr. Baron explains how the vaccine is placed just under the skin to trigger an immune response: "White blood cells in your skin see these foreign cells. They’re stimulated then to respond to them, if you will, and train your immune system to make perhaps antibodies or t-cells against the prostate cancer." GVAX is specifically designed for metastatic prostate cancer.

Dr. Baron says that early data have been promising, and the current Phase 3 trials will provide additional data to determine how effective the vaccine is in treating prostate cancer. California Pacific Medical Center is recruiting patients for its clinical trials.

Source: AB News/KGO TV (7/7/07)