New study indicates that it will be a very effective alternative endocrine therapy for individuals with recurrent endometrial cancer who have tumors that express the estrogen receptor.

According to the findings of a recent clinical trial, a combined therapy that targets cancer cells from within and without caused tumors to shrink or stabilize in 75 percent of patients with recurrent or persistent estrogen receptor-positive endometrial cancer.

The phase 2 study examined the combination of abemaciclib, a targeted agent, and letrozole, an aromatase inhibitor, in 30 patients with recurrent ER-positive endometrial cancer, a kind of cancer in which tumor growth is fuelled by estrogen. The patients had undergone a median of three previous therapies, with hormonal therapy being used by about half of them.

With a median follow-up of 12.5 months, 75 percent of patients saw their tumors decrease or stabilize. The tumors of approximately 30 percent of the individuals shrank by more than 30 percent. The benefits were long-lasting: it took an average of 9.1 months for the condition to worsen.

Only two patients dropped out of the research subject to severe adverse effects from the two-drug regimen. Some individuals continued to benefit from the medication and stayed in the study for over a year. Two of them have been on it for almost two years.

“When we compare the efficacy of this regimen with that of other endocrine therapies for endometrial cancer, we can see this combination is extremely promising,” said Panagiotis Konstantinopo.

Endometrial cancer, which starts in the uterine lining, is the sixth most frequent cancer in the world, with over 400,000 women diagnosed each year. ER-positive endometrial cancers account for the majority of endometrial tumors.

Patients whose cancer has started to grow after chemotherapy and immunotherapy, or whose cancer is slow-growing and generates relatively modest symptoms, may benefit from endocrine therapy, which aims to lower the amount of estrogen reaching tumor cells. Researchers are looking for strategies to improve the efficacy of this type of therapy because the advantages are usually minor and short-lived.

Letrozole reduces total estrogen levels by inhibiting an enzyme in adipose tissue from turning some hormones to estrogen. Abemaciclib inhibits the CDK4 and CDK6 proteins, both of which are important for cell growth. Combining these drugs gives ER-positive endometrial cancer cells a two-pronged attack, removing a vital gear in their development mechanism while reducing estrogen availability.

Responses to the regimen were seen regardless of a tumor’s grade (how aberrant its cells seem under a microscope), prior hormone therapy, or the presence or absence of progesterone receptors on tumor cells, according to an analysis of patients’ tumor tissue. Patients with mutations in the KRAS, CTNNB1, or CDK2NA genes reacted to the medication 100% of the time, but those with TP53 mutations were less likely to respond.

“Based on our findings, the letrozole/abemaciclib combination should be considered worthy of further evaluation for patients with recurrent ER-positive endometrial cancer,” Konstantinopoulos added.

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