AstraZeneca's Camizestrant Shows Promise in Extending Breast Cancer Treatment

A new experimental drug from AstraZeneca could significantly improve outcomes for patients with the most common type of breast cancer. Data presented at the American Society of Clinical Oncology (ASCO) annual meeting revealed that camizestrant, a selective estrogen receptor degrader (SERD), substantially reduced the risk of disease progression or death in patients with hormone receptor-positive, HER2-negative advanced breast cancer.

Camizestrant's Breakthrough in Breast Cancer Treatment

The SERENA-6 trial, led by Dr. Nicholas Turner of the Royal Marsden Hospital in London, enrolled 3,256 patients with advanced hormone receptor-positive, HER2-negative breast cancer. Participants were monitored for the emergence of ESR1 mutations, which occur in about 40% of patients during initial therapy and can drive cancer growth even as first-line treatments become less effective.

When ESR1 mutations were detected in approximately 550 patients, 315 were randomly assigned to either switch to camizestrant or continue their initial regimen. The results were striking: patients who switched to camizestrant experienced a 56% lower risk of disease progression or death compared to those who continued their original treatment. Median progression-free survival increased from 9.2 months in the control group to 16 months in the camizestrant group.

Dr. Turner emphasized the urgent need for new treatments, stating, "Patients have an urgent need for new treatments that can prolong time on first-line therapy and delay disease progression."

Innovative Approach to Cancer Treatment

Camizestrant represents a novel approach to treating breast cancer by breaking down the estrogen receptor entirely. This mechanism allows it to potentially overcome the resistance that develops due to ESR1 mutations, which change the shape of the estrogen receptor and keep it in an "on" state.

The drug is part of a new class of orally administered SERDs, which offer advantages over older injectable treatments like fulvestrant. One SERD, Orserdu, has already received U.S. approval in 2023, while others from companies such as Eli Lilly, Roche, and a partnership between Pfizer and Arvinas are in late-stage testing.

Implications for Patient Care and Clinical Practice

The SERENA-6 trial introduces a potentially game-changing approach to breast cancer treatment by intervening before initial disease progression. Dr. Eleonora Teplinsky, head of breast and gynecologic medical oncology at New Jersey's Valley-Mount Sinai Comprehensive Cancer Care, highlighted the importance of this strategy: "When patients progress on scans, we're already behind. We've already lost control, in some sense. An early switch approach, before we see disease progression on imaging, [allows] us to stay ahead of the curve."

This approach relies on regular monitoring through "liquid biopsies," which detect tumor DNA fragments in the blood. While these tests are relatively expensive, Dr. Turner expressed hope that insurance would cover them if camizestrant gains approval in this setting.

The potential approval of camizestrant could also lead to changes in testing practices. ASCO recently updated its guidelines to recommend testing for ESR1 mutations following disease progression or recurrence. However, camizestrant's benefit lies in delaying that progression, necessitating earlier and more frequent monitoring.

Dr. Julie Gralow, ASCO's chief medical officer, noted, "The difference here is this serial monitoring for evidence of the evolving mutation."

AstraZeneca plans to use the SERENA-6 data to seek regulatory approval for camizestrant. The company is also conducting studies on using the drug as a first-line treatment and exploring its potential in early breast cancer.

As the pharmaceutical industry continues to innovate in cancer treatment, camizestrant represents a significant step forward in the ongoing battle against breast cancer, potentially offering patients more time with effective first-line therapy and an improved quality of life.