Several large clinical trials have shown that tamoxifen can decrease the risk of breast cancer in high-risk women. There are, however, two issues that have prevented widespread use of tamoxifen for breast cancer prevention:

* Who is at risk? The definition of who is high risk is problematic and differs from trial to trial. Generally, high risk includes women with a family history of breast cancer, early menarche, later or no childbirth, or previous breast biopsy, even if negative.

* What are the side effects? In one study, it was found that less than one in five women at high risk would take tamoxifen due to their fears of side effects and the fact that they assumed they were at relatively low risk for developing breast cancer.

Two reports in the February 21, 2007 issue of the Journal of the National Cancer Institute document that tamoxifen can prevent hormone-positive breast cancer in women at high risk.

Researchers affiliated with the Royal Marsden Randomized, Double-Blinded Tamoxifen Breast Cancer Prevention Trial reported 20-year follow-up data. This trial randomly allocated 2,494 women at high risk of developing breast cancer to receive tamoxifen or placebo for eight years. A total of 82 women in the tamoxifen group and 104 in the placebo group developed invasive breast cancer. Researchers affiliated with the first International Breast Cancer Intervention Study (IBIS-I) reported that the breast cancer preventative effects of tamoxifen persist for at least 10 years after a five-year treatment period. This trial randomly allocated 7,145 women at increased risk for developing breast cancer to receive five years of tamoxifen or placebo. With a 96-month follow-up, there were 142 breast cancers in the tamoxifen group and 195 in the placebo group. They observed a preventive effect during the entire period of observation. The main side effects were an increased risk of deep-vein thrombosis and pulmonary embolism during but not after tamoxifen treatment. The estimated risk for developing estrogen receptor-positive breast cancer was 34% lower in the tamoxifen group.

The authors of the present trial sought to determine why few women with increased risk of breast cancer use tamoxifen for chemoprevention. They evaluated 632 women with an average 2.56% risk of developing breast cancer within five years. These women were presented with a tailored decision aid concerning the effectiveness of chemoprevention with tamoxifen and the known side effects. After reviewing the decision aid, 29% of women said they would seek more information from their own physician, and 6% said they would agree to take tamoxifen. These researchers thought that these women had adequate knowledge to make a decision. The stated: “Participants were concerned about the risks of tamoxifen, and many believed that the benefits of tamoxifen did not outweigh the risks.”

Discovering Key to Tamoxifen’s Effectiveness in Treating Breast Cancer may Mean New Treatments

After working initially with human cancer cell lines, Ines Diaz-Laviada and colleagues from the University of Alcala in Madrid also tested one compound on mice and discovered it produced a significant reduction in tumor growth. Their research, published in the British Journal of Cancer, underlines the growing interest in the medical use of active chemicals called cannabinoids, which are found in marijuana.

Experts, however, stressed that the research was still exploratory and many more years of testing would be needed to work out how to apply the findings to the treatment of cancer in humans.

“This is interesting research which opens a new avenue to explore potential drug targets but it is at a very early stage,” said Lesley Walker, director of cancer information at Cancer Research UK, which owns the journal. “It absolutely isn’t the case that men might be able to fight prostate cancer by smoking cannabis,” she added

The cannabinoids tested by the Spanish team are thought to work against prostate cancer because they block a receptor, or molecular doorway, on the surface of tumour cells. This stops them from dividing. In effect, the cancer cell receptors can recognize and “talk to” chemicals found in cannabis, said Diaz-Laviada.

“These chemicals can stop the division and growth of prostate cancer cells and could become a target for new research into potential drugs to treat prostate cancer,” she said. Her team’s work with two cannabinoids — called methanandamide and JWH-015 — is the first demonstration that such cannabis chemicals prevent cancer cells from multiplying.

Some drug companies are already exploring the possibilities of cannabinoids in cancer, including British-based cannabis medicine specialist GW Pharmaceuticals. It is collaborating with Japan’s Otsuka on early-stage research into using cannabis extracts to tackle prostate cancer — the most commonly diagnosed cancer in men — as well as breast and brain cancer.

GW has already developed an under-the-tongue spray called Sativex for the relief of some of the symptoms of multiple sclerosis, which it plans to market in Europe with Bayer and Almirall. Other attempts to exploit the cannibinoid system have met with mixed success. Sanofi-Aventis was forced to withdraw its weight-loss drug Acomplia from the market last year because of links to mental disorders.

Cruel Treatment of Medical Marijuana Patient video posted by Sandy Hutchens Cancer Prevention

Researchers from Fred Hutchinson Cancer Research Center in Seattle looked at 728 women diagnosed with breast cancer. Those women were compared to 367 others diagnosed with both a first and second breast cancer.

The main finding from the study, published online Tuesday in the journal Cancer Research, was that tamoxifen lowered the risk of any second breast cancer overall by about half, said lead author Dr. Christopher Li.

“For the estrogen receptor-positive cancer, we have targeted therapy that again has been proven to again reduce mortality,” said Li. “That’s one of the reasons why ER-negative cancers are more worrisome because we don’t have a targeted treatment for them.”

Li said it’s important to remember that any treatment has risks and benefits associated with it, and tamoxifen is no exception.

Tamoxifen lowers breast cancer patients’ risk of dying of the disease, and has also been shown to lower a woman’s risk of developing a recurrent breast cancer and a second breast cancer, he noted. But use of tamoxifen also comes with risk of stroke, as well as the risk of endometrial cancer, he added.

“So here we’re finding that we’re adding potentially another risk to the risk-benefit equation,” Li said. “We’re finding that there is this increased risk in this more aggressive subtype of second breast cancer. However, we also overall found using tamoxifen did lower the risk of any type of second breast cancer overall.”

“For that reason, we don’t really think that this study changes the overall risk-benefit equation because the benefits for most women who are eligible to use this treatment are going to still outweigh the risks.”

Every tumour is a mix of receptor-positive and receptor-negative cells, she said. If the types of cells that predominate are receptor-negative, it gets read as an increased risk of receptor-negative breast cancer if tamoxifen is taken for five or more years.

Dr. Jay Harness,Tamoxifen And The Side Effects put up by Sandy Hutchens.

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The research released Wednesday is the first to show Iressa can be more effective than chemotherapy as a first-line treatment, and some experts are hopeful it will prompt the Food and Drug Administration to allow wide use of the drug, made by AstraZeneca PLC. Others are skeptical. Though the study shows an effect on cancer growth over one year, the drug’s impact on long-term survival is still in question. Also, the study was done in Asia, and the drug seems to work best with specific patients — Asians, women and nonsmokers who carry a specific gene mutation.

“I’d venture to say that additional studies will be requested in the United States population,” said Dr. Len Lichtenfeld, the American Cancer Society’s deputy chief medical officer.

AstraZeneca, which funded the study, is not planning a new push for expanded FDA approval of the drug, a company spokeswoman said. But the company is continuing to share data about the drug with federal health officials, she added.

Iressa is a daily pill that more precisely targets cancer rather than healthy cells. It’s an attractive alternative to standard chemotherapy, which involves trips to a hospital or clinic for infusions of poisonous chemicals that cause nausea and hair loss. In 2003, the FDA approved Iressa as a last-resort treatment for patients with the most common form of lung cancer, called non-small-cell lung cancer. The market was significant: Lung cancer kills more Americans than any other kind of tumor, and the Cancer Society estimates it will cause nearly 160,000 U.S. deaths this year. Non-small-cell lung cancer represents 85 percent of lung cancer cases.

But in 2005, the FDA stopped allowing new patients to go on Iressa after early results from a federally sponsored study failed to show it improved lung cancer patients’ survival rates. Another lung cancer pill, Roche Group’s Tarceva, acts in a way similar to Iressa and remained on the market as a treatment for patients not helped by chemotherapy. There wasn’t widespread outcry at the loss of Iressa because Tarceva remained available, said Dr. Edward Kim, a lung cancer specialist at the University of Texas M.D. Anderson Cancer Center.

Interest in Iressa continued, though, as doctors have become increasingly interested in personalized approaches to cancer treatment. Studies have shown some drugs work better in certain breast and colon cancer patients than others, and earlier studies have found that Iressa dramatically shrunk tumors in patients who had lung cancers with a specific genetic mutation. That kind of scenario is observed in only a small fraction of U.S. lung cancer patients, but is much more common in Asia, scientists say.

The latest study was led by Dr. Tony Mok of the Chinese University of Hong Kong, and involved about 1,200 patients throughout southeast Asia. The study group included the kind of people most likely to have the mutation, said Dr. Pasi Janne, a Dana-Farber Cancer Institute lung cancer specialist.

The study measured cancer growth within a year after treatment, comparing patients who got Iressa to others who got chemotherapy. After one year, 25 percent on Iressa were alive without their cancer getting worse, as compared to 7 percent of those on chemo. Results were even better in those with the mutation. In those without the mutation, chemotherapy was more effective. The study was published online Wednesday by the New England Journal of Medicine. A second study released by the journal concluded that large-scale screening of lung cancer patients for the genetic mutation is feasible and can lead to wiser treatment.

Cancer Facts : How Does Lung Cancer Develop? embedded by Sandy Hutchens

Lung cancer develops when smoking, air pollutants and free radical formation damages sensitive lung tissue, causing the cellular DNA to restructure and malfunction. Avoid lung cancer by quitting smoking with information from a doctor in this free video on cancer.

Expert: Dr. David Cathcart
Bio: Dr. David Cathcart specializes in occupational medicine and has an in-depth knowledge of cancer, as well as experience dealing with cancer patients and treatment for multiple years.