Aromatase Inhibitors for Breast Cancer

 

Majid Ali, M.D.

Does Extending the Use of Aromatase-Inhibitor Drugs  for Ten Years Increase Overall Survival Rate?

The Answer of a 2016 Trial: No.

Please carefully the text from the trial report.


Below is the conclusion of a trial published in The New England Journal of Medicine on July 21, 2016. The abstract of results of the trial are included below.

“The extension of treatment with an adjuvant aromatase inhibitor to 10 years resulted in significantly higher rates of disease-free survival and a lower incidence of contralateral breast cancer than those with placebo, but the rate of overall survival was not higher with the aromatase inhibitor than with placebo.”

“We showed that treatment with an aromatase inhibitor for an additional 5 years after initial treatment for 4.5 to 6 years was beneficial in preventing disease recurrence, independent of nodal status, prior adjuvant chemotherapy, time since the last dose of aromatase inhibitor, and duration of prior therapy with tamoxifen or an aromatase inhibitor. The risk of disease recurrence and contralateral breast cancer was significantly lower (by 34%) among women who continued aromatase inhibitor for 10 years than among women who received placebo after the initial 5 years of aromatase-inhibitor therapy. No overall difference in survival was noted at a median follow-up of 6.3 years. The significant benefit in disease-free survival includes not only a numerically larger reduction in events of local, regional, and distant recurrence but also an apparently greater proportional reduction in events of contralateral breast cancer, which may partly explain the absence thus far of an observed overall survival benefit.”


 

 

 


 

Trial Outcome

Goss PE, Ingle JN, Pritchard KI, et al. Extending Aromatase-Inhibitor Adjuvant Therapy to 10 Years. N Engl J Med 2016; 375:209-219.

RESULTS

We enrolled 1918 women. After a median follow-up of 6.3 years, there were 165 events involving disease recurrence or the occurrence of contralateral breast cancer (67 with letrozole and 98 with placebo) and 200 deaths (100 in each group). The 5-year disease-free survival rate was 95% (95% confidence interval [CI], 93 to 96) with letrozole and 91% (95% CI; 89 to 93) with placebo (hazard ratio for disease recurrence or the occurrence of contralateral breast cancer, 0.66; P=0.01 by a two-sided log-rank test stratified according to nodal status, prior adjuvant chemotherapy, the interval from the last dose of aromatase-inhibitor therapy, and the duration of treatment with tamoxifen). The rate of 5-year overall survival was 93% (95% CI, 92 to 95) with letrozole and 94% (95% CI, 92 to 95) with placebo (hazard ratio, 0.97; P=0.83). The annual incidence rate of contralateral breast cancer in the letrozole group was 0.21% (95% CI, 0.10 to 0.32), and the rate in the placebo group was 0.49% (95% CI, 0.32 to 0.67) (hazard ratio, 0.42; P=0.007). Bone-related toxic effects occurred more frequently among patients receiving letrozole than among those receiving placebo, including a higher incidence of bone pain, bone fractures, and new-onset osteoporosis. No significant differences between letrozole and placebo were observed in scores on most subscales measuring quality of life.

CONCLUSIONS

The extension of treatment with an adjuvant aromatase inhibitor to 10 years resulted in significantly higher rates of disease-free survival and a lower incidence of contralateral breast cancer than those with placebo, but the rate of overall survival was not higher with the aromatase inhibitor than with placebo.

 

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BACKGROUND

Treatment with an aromatase inhibitor for 5 years as up-front monotherapy or after tamoxifen therapy is the treatment of choice for hormone-receptor–positive early breast cancer in postmenopausal women. Extending treatment with an aromatase inhibitor to 10 years may further reduce the risk of breast-cancer recurrence.

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