Hope for Advanced Breast Cancer: New Combination Therapy Shows Promise Against Leptomeningeal Metastasis

For women with HER2-positive breast cancer that has spread to the brain, a new combination therapy is offering a significant improvement in survival and quality of life. Researchers at MD Anderson Cancer Center have found that a regimen of tucatinib, trastuzumab and capecitabine can extend survival and improve neurological symptoms in patients with leptomeningeal metastasis (LM), a rare but devastating complication of breast cancer.

Understanding Leptomeningeal Metastasis

Leptomeningeal metastasis occurs when cancer cells spread to the leptomeninges – the thin layers of tissue and fluid that surround the brain and spinal cord ¹. Unlike a solid tumor in the brain, LM involves cancer cells dispersing within the cerebrospinal fluid, making treatment particularly challenging. Symptoms can include headaches, balance disorders, partial paralysis, and epileptic seizures.

Challenges in Treating Leptomeningeal Metastasis

Treating LM is complicated by the blood-brain barrier, which prevents many drugs from reaching the cerebrospinal fluid. Traditional treatments have included radiotherapy and intrathecal injections (directly into the spinal cord). However, these options often provide limited relief and have significant side effects.

The TBCRC049 Trial: A New Approach

The recent Phase II TBCRC049 trial, published in Nature Cancer ², evaluated the combination of tucatinib, trastuzumab, and capecitabine in 17 women with newly diagnosed HER2-positive breast cancer and LM. The regimen consisted of 21-day cycles of tucatinib twice daily, oral capecitabine, and trastuzumab infusion every three weeks.

Significant Improvement in Survival

The results of the trial were encouraging. The median overall survival (OS) increased from a historical average of 4.4 months to 10 months ¹. At the 18-month mark, 41% of patients were still alive ¹. The median time to central nervous system progression was 6.9 months ².

Improved Neurological Symptoms and Manageable Side Effects

In addition to improved survival, the combination therapy also led to improvements in neurological symptoms. Seven of 12 patients evaluated experienced improvements in their neurological deficits ¹. The side effects, including diarrhea, nausea, vomiting, hand-foot syndrome, and increased liver enzymes, were generally considered manageable.

Tucatinib Reaches the Brain

Researchers found that tucatinib reached therapeutic levels in the cerebrospinal fluid, suggesting it can effectively target cancer cells in the brain and spinal cord ². This is a significant finding, as many drugs struggle to cross the blood-brain barrier.

Looking Ahead

While the TBCRC049 trial was limited to a small number of patients, the results offer a promising new treatment option for women with HER2-positive breast cancer and leptomeningeal metastasis. “The combination achieved a clinically meaningful improvement in overall survival compared to historical controls,” said Rashmi Murthy, M.D., associate professor of Breast Medical Oncology ¹. Further research is needed to confirm these findings in larger trials and to explore the potential of this combination therapy in other types of cancer that metastasize to the brain. This research represents a step forward, offering new hope for patients facing this challenging diagnosis ³.