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Higher Faslodex Dose Better for Recurrent or Metastatic Breast Cancer

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Faslodex (chemical name: fulvestrant) is a type of hormonal therapy medicine used to treat postmenopausal women diagnosed with advanced-stage hormone-receptor-positive breast cancer in two situations:

  • if the cancer failed to respond or stopped responding to another hormonal therapy (tamoxifen, for example)
  • if the cancer is a recurrence of early-stage breast cancer that developed while a woman is taking hormonal therapy

Hormonal therapy medicines work by blocking the effects of estrogen on breast cancer cells or by lowering the amount of estrogen the body produces.

A study has found that women diagnosed with recurrent or metastatic hormone-receptor-positive breast cancer lived longer when they got 500 mg of Faslodex (double the usual dose) compared to women who got 250 mg of Faslodex (the usual dose).

Recurrent breast cancer is cancer that has come back after initial diagnosis and treatment. Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver. Both recurrent and metastatic breast cancer are advanced-stage breast cancer.

The study, "Final analysis of overall survival for the phase III CONFIRM trial: Fulvestrant 500 mg versus 250 mg," was presented at the 2012 San Antonio Breast Cancer Symposium.

Faslodex is an estrogen receptor downregulator (ERD). Like tamoxifen, Faslodex works by blocking estrogen receptors. Faslodex sits in the estrogen receptors in breast cells. If Faslodex is in the estrogen receptor, there is no room for estrogen and it can't attach to the cell. If estrogen isn't attached to a breast cell, the cell doesn't receive estrogen's signals to grow and multiply. Faslodex also:

  • reduces the number of estrogen receptors
  • changes the shape of breast cell estrogen receptors so they don't work as well

Faslodex is injected into a muscle once a month.

The results are a follow-up analysis of the CONFIRM (Comparison of Faslodex in Recurrent or Metastatic Breast Cancer) trial. The study randomly assigned 736 women diagnosed with estrogen-receptor-positive breast cancer that was recurrent or metastatic after treatment with either tamoxifen or an aromatase inhibitor to get either 250 mg or 500 mg of Faslodex.

At the 2009 San Antonio Breast Cancer Symposium, the researchers reported that the CONFIRM trial showed that the 500 mg dose of Faslodex was linked to better progression-free-survival (the length of time the women lived without the cancer growing). The results also suggested that the 500 mg dose of Faslodex might improve overall survival (how long the women lived, with or without the cancer growing), but the difference wasn’t statistically significant, which means that it might have been due to chance and not because of the difference in Faslodex dose.

Because some doctors believe that the 250 mg dose of Faslodex is too low, the researchers decided to reanalyze the data from the women in the CONFRIM trial who were still alive to see if the 500 mg dose did improve overall survival.

With 3 more years of follow-up information, the researchers found that the 500 mg dose of Faslodex improved overall survival by more than 4 months compared to the 250 mg dose.

Side effects and overall quality of life were about the same for all the women no matter which dose of Faslodex they got.

If you’ve been diagnosed with recurrent or metastatic hormone-receptor-positive breast cancer, you and your doctor will consider a number of treatment options, including hormonal therapy and chemotherapy. Because the breast cancer is hormone-receptor-positive, hormonal therapy medicines are still good treatment options even if you’ve been treated with hormonal therapy in the past. Faslodex, which works differently than tamoxifen and the aromatase inhibitors, might be a good choice, depending on your unique situation. If your doctor does recommend Faslodex, you might want to ask how much you’ll receive. If the standard dose (250 mg) is recommended, consider asking your doctor about this study and whether the higher 500 mg dose makes sense for you. Together, you and your doctor will decide on a treatment plan that’s best for you.

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