For more than three decades the go-to drug for breast cancer patients that interferes with the activity of estrogen, tamoxifen may also be valuable in reducing the risk of death for folks fighting lung cancer.

Scientists monitored the health of more than 6,600 female patients registered with the Geneva Cancer Registry in Switzerland, who had been diagnosed with breast cancer between 1980-2003, until the end of 2007 for the incidence and death from lung cancer. Nearly half (3,066) of those patients participating in the study received anti-estrogen therapy.

Overall, just 40 patients developed lung cancer, statistically small by any measure and not much different statistically between women participating in the study and cases among the general population. The real difference -- 87 percent -- was the declining number of cases leading to death from lung cancer while taking anti-estrogen therapy among patients in the study group compared to the general population.

BTW, check with your doctor to ensure you're not taking a drug -- an SSRI like Prozac or Paxil -- that suppresses the CYP2DG enzyme, a critical trigger that allows tamoxifen to do its job.

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If you're taking medications -- for example, a selective serotonin reuptake inhibitor (SSRI) such as fluoxetine (Prozac) or paroxetine (Paxil) -- or other antipsychotic or cardiac drugs and you're a female patient taking tamoxifen, you may want to schedule an appointment with your doctor very soon.

The problem: Some drugs suppress the presence of the CYP2DG enzyme, a critical trigger that allows the liver to convert tamoxifen into the more active endoxifen that, in turn, may prevent breast cancer or a repeat battle with this frightening disease.

Follow-up research to previous studies conducted at the Mayo Clinic College of Medicine that identified fluoxetene and paroxetene as potentially harmful for breast cancer patients taking tamoxifen has expanded the list of drugs inhibiting CYP2D6 levels to include drugs that treat infectious diseases, depression, psychosis and heart problems. (Check the Medscape link below for a full list of drugs that affect CYP2DG levels and many alternatives.)

As a result of this research, the Mayo Clinic has been testing breast cancer patients for the CYP2DG enzyme before prescribing tamoxifen in excess of three years, considered a controversial practice among some experts.

Still, there's no question, avoiding drugs that interact poorly with tamoxifen is the best course of action for patients taking tamoxifen. For your own peace of mind, however, PLEASE do your homework and talk to your doctor before making any changes to your treatment regimen.

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Journal of Clinical Oncology, Vol. 28, No. 16, pp. 2768-2776, June 1, 2010

Medscape May 5, 2010 Free Subscription/Registration Required

HealthCentral June 1, 2009