Sunday, April 04, 2004

Apparently some think that its not being used enough.....

A drug that cuts the rate of breast cancer by 50 percent in women most at risk is not being used as much as it could be, because doctors are failing to offer it and some patients are confused about taking it, researchers reported Monday.

Women may be afraid to take the drug tamoxifen because it raises the risk of cancer of the uterus, as well as the risk of blood clots that can cause heart attacks, embolisms or strokes, the team at Northwestern Memorial Hospital in Chicago found.

They looked at the records of 219 women with higher-than-average breast cancer risk. Only 63 percent of the women were offered tamoxifen and only 26 percent accepted, they found......

Tamoxifen, a pill used to treat breast cancer, has been shown to reduce cancer rates by 49 percent in women who have a high risk of the disease either because they have had precancerous lesions, a strong family history, or for other reasons.

My goodness, why wouldn't women want to reduce their breast cancer risk by almost half? This article has fallen prey to the old statistical bogeyman of absolute versus relative risk, and how that effects decision-making. The basis for those recommendations is the NSABP P-1 trial A Clinical Trial to Determine the Worth of Tamoxifen for Preventing Breast Cancer, also known as the Breast Cancer Prevention Trial or BCPT. The results, found here indicate that 368 out of 13175 women had either invasive or in situ cancers diagnosed during the follow-up period, an incidence of 2.79 percent. In the placebo group 244 out of 6707, or 3.64 percent had a cancer diagnosed, compared with 124/6681 or 1.86 percent in the Tamoxifen group. So while the absolute reduction of breast cancer was by about 1.8 percent, the relative risk numbers get the play. More on how that affects decision making later on. As expected the absolute and relative risk numbers were better in patients with atypical ductal hyperplasia and lobular carcinoma in situ. Of the Tamoxifen group 18 out of 6681 (0.26 percent) developed a pulmonary embolus, compared to 0.089 percent (6/6707) in the placebo group (RR=3.01), 0.52 percent developed a DVT, compared with 0.32 percent in the placebo group (RR=1.6), and for endometrial cancer 36 of 6681 in the Tamoxifen group (.053 percent) had a diagnosis, compared with 15/6707 (0.22 percent) in the placebo group (RR=2.53). Of course the risks were higher in women greater than age 50, and the prevention benefits of Tamoxifen also start to increase after that age.

So while taking this medication may reduce your risk of developing breast cancer by fifty percent , it can raise your risk of endometrial cancer 150%, increase the risk of DVT by 60% and raise the risk of PE by 200%. It can cause an increased chance of uterine sarcoma and cataracts as well.

Now if the woman has had a hysterectomy, the endometrial cancer risk is eliminated, and the endometrial cancer is diagnosed at an early stage if a uterus is present. The risk of thromboembolic disease is roughly equivalent to that of HRT. But those numbers can be plenty worrisome for woman considering this for prevention.

Determining risk has been assisted by computer-based Gail algorithms. Such tools may be found here and here. They will take a number of factors such as age at menarche, relatives with breast cancer, gravidy and parity, and number of biopsies done to deliver 5-year and lifetime estimated absolute risks. Anything above 1.6%-1.7% is considered "high risk". The participants in the BCPT all had a risk percentage >1.66%.

So when a woman is told that her risk of developing breast cancer over the next five years is 2 percent (meaning her chances of NOT developing breast cancer is 98%) and we can reduce her risk to one percent with Tamoxifen, with the side effects described above. Not as dramatic as made out by the relative risk, is it? Tamoxifen isn't cheap either with a months supply running about $60.

In my own practice I offer Tamoxifen to patients with LCIS or atypical ductal hyperplasia. I discuss the risks and benefits and give them some literature to review. They return in a few weeks and we discuss it some more. About 1/3 of the patients start on Tamoxifen. Studies comparing Tamoxifen with other agents, such as the STAR trial are ongoing.
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