Targeted neutron therapy shrinks tumors in five patients with recurrent breast cancer

Five patients with recurrent triple-negative breast cancer had their tumors shrink markedly after receiving boron neutron capture therapy, or BNCT, through a compassionate-use program in Taiwan. The collaboration between National Tsing Hua University, Taipei Veterans General Hospital and Far Eastern Memorial Hospital also reported little damage to nearby normal tissue.

BNCT combines a boron-containing drug, designed to accumulate preferentially in tumor cells, with a neutron beam. When boron captures a neutron, it releases high-energy particles across a distance of roughly one cell, helping concentrate radiation’s destructive effect within the tumor. This precision could be especially useful in triple-negative breast cancer, which lacks the estrogen, progesterone and HER2 receptors targeted by several established treatments and therefore has fewer therapeutic options and a higher risk of recurrence.

The findings are encouraging but preliminary. BNCT is currently being used as a local salvage treatment, not as a replacement for surgery or medicines that work throughout the body. The five cases were compassionate-use treatments rather than a breast cancer clinical trial. The team plans to build a larger evidence base and longer follow-up before pursuing such a trial.

The work builds on an earlier published case series involving recurrent breast cancer and brain metastases, in which all irradiated tumors in the brain became smaller and some symptoms improved.