Personalized Breast Cancer Treatment Shows Promise for Tamoxifen Non-Responders
A new German study offers a potential breakthrough for women with hormone receptor-positive (ER/PR+) breast cancer who don’t respond optimally to standard tamoxifen therapy. Researchers have discovered that tailoring treatment based on an individual’s metabolism of the drug can considerably improve its effectiveness.
Hormone receptor-positive breast cancer, the most common type of the disease, is fueled by estrogen and progesterone. Hormone therapy aims to block or reduce the impact of these hormones, thereby slowing or stopping cancer cell growth. Because estrogen and progesterone levels are higher before menopause, this type of cancer is more frequently diagnosed in younger women.
For patients whose cancer doesn’t respond sufficiently to tamoxifen – a decades-old mainstay of breast cancer treatment – a new approach is showing promise. Researchers found that adding (Z)-endoxifen, the active form of tamoxifen, to the treatment regimen can dramatically increase its efficacy.
Tamoxifen functions by preventing estrogen from attaching to receptors on tumor cells, effectively halting their proliferation. Though, the drug requires conversion within the body by an enzyme called CYP2D6 into (Z)-endoxifen to achieve its full therapeutic effect. Approximately one-third of patients possess lower levels of this enzyme due to genetic factors, hindering the drug’s activation and diminishing its impact.
While aromatase inhibitors offer an alternative for postmenopausal women, these are not suitable for younger patients.
The study, recently published in Clinical Cancer Research, suggests that directly administering (Z)-endoxifen can bypass the need for CYP2D6, restoring the effectiveness of hormonal treatment.
The research team evaluated 235 women diagnosed with early-stage, hormone-induced breast cancer.Participants received either tamoxifen alone or a combination of tamoxifen and (Z)-endoxifen, steadfast by their individual metabolic profiles. those receiving the combination therapy achieved blood concentrations of the active drug comparable to those seen in patients who naturally metabolize tamoxifen effectively, indicating similar treatment benefits.
reported side effects were mild and consistent across both groups, suggesting that supplementing with (Z)-endoxifen is well-tolerated.
“Through this approach we offer the first effective solution to a long-standing problem: the insufficient effect of tamoxifen in a important number of patients,” stated a study leader at the Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology.
Why this matters: Women with hormone receptor-positive breast cancer who don’t respond to tamoxifen have limited treatment options, notably if they are premenopausal. This study offers a potential solution by directly providing the active form of the drug, bypassing a common metabolic bottleneck.
Who was involved: Researchers at the Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology in Germany led the study, which involved 235 women diagnosed with early-stage, hormone-induced breast cancer.
What happened: The study demonstrated that adding (Z)-endoxifen to tamoxifen treatment for patients with low CYP2D6 enzyme activity resulted in improved drug concentrations and potentially similar treatment benefits as those who metabolize tamoxifen effectively.
How it was studied: Researchers conducted a clinical trial comparing tamoxifen alone to a combination of tamoxifen and (Z)-endoxifen, tailoring the treatment based on each participant’s metabolic profile.They measured blood concentrations of the active drug and monitored side effects.
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