Erik J. Blok, MD, Department of Medical Oncology at Leiden University Medical Center, discusses the duration of adjuvant endocrine therapy. Blok claims that there is no breast cancer survival benefit in extending adjuvant letrozole treatment from 2.5 to 5 years.

In the trial, 70% of patients reporting experiencing toxicities. The most common toxicities were arthralgia, hot flashes, and osteoporosis.

While the extension of adjuvant letrozole therapy has no survival benefit, Blok said that waiting for a subgroup analysis on this treatment could reveal groups of patients with breast cancer who could benefit from extended therapy. There are currently genomic assays being developed to explore this possibility.

With a longer duration of treatment, Blok says that there is a significant difference in the occurrence of primary breast cancers, which was also observed in the MA-17R trial. Longer duration was associated with fewer new primary breast cancer tumors, and Blok suggests that the medical community should decide if this is a goal of adjuvant therapy.

Erik J. Blok, MD

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Dr. Blok on Results of Adjuvant Letrozole Study in Breast Cancer