Editorial: Recent advances in boron neutron capture therapy in radiation oncology

Editorial on the Research Topic
Recent advances in boron neutron capture therapy in radiation oncology

In this Research Topic, “Recent Advances in Boron Neutron Capture Therapy in Radiation Oncology”, there were four papers published. Hsu et al. discussed developing a tumor control probability (TCP) model from a clinical trial done in Taiwan for recurrent head and neck (H&N) cancer. Their analysis showed the generalized Equivalent Uniform Dose (gEUD)–based TCP model (derived from the universal survival curve (USC) model) correlated well with the tumor response and dose distribution of recurrent H&N cancer. The recommended minimal tumor dose (18 Gy-w in a single fraction) can be used as a reference dose for future curative BNCT in this challenging scenario.

The impact of BNCT on the immune system is seldom explored. The second paper by Chang et al. is a basic study investigating the association of M-MDSCs(monocytic myeloid-derived suppressive cells) depletion with the therapeutic effect of BNCT in mice bearing oral squamous cell carcinoma. Myeloid-derived suppressor cells are a heterogeneous population of myeloid cells that appear in the tumor microenvironment (TME) and can modulate immune response. They found that M-MDSCs with CSF-1 receptors were recruited into murine tumors after BNCT, and their number was also increased in peripheral blood. The administration of PLX-3397, a CSF-1 receptor inhibitor, could hinder BNCT-caused M-MDSCs infiltration, prolong mice survival, and activate tumor immunity. This may be useful for the design of future trials combining immunotherapy and BNCT for recurrent H&N cancer.

Accelerator-based BNCT (AB-BNCT) systems installed in hospitals is becoming a reality. There were two papers on this topic corelated with AB-BNCT. The third paper by Igaki et al. showed the result of an acral cutaneous malignant melanoma treated with AB-BNCT at the National Cancer Center Hospital, Tokyo, Japan. The maximum dose delivered to the skin was 18 Gy-Eq. The skin lesion disappeared completely within 12 months. Adverse effects including dermatitis, dry skin, skin hyperpigmentation, and edema were mild (only grade 1). This case report showed that AB-BNCT may be a promising treatment modality for cutaneous malignant melanoma.

The fourth paper by You et al. explored out-of-field leakage from the neutron beam of the AB-BNCT system installed in a hospital in Zhubei, Taiwan. The out-of-field leakage dose, also called a non-target radiation dose, is of concern in AB-BNCT because it causes unnecessary risk of harm to patients. Therefore, it is important to consider out-of-field leakage in beam shaping assembly (BSA) design. Calculation in this study found that the whole-body dose in their system was low. In the near future, we expect to see more studies reporting results from both basic and clinical research on AB-BNCT.

Author contributions

L-WW: Writing – original draft, Writing – review & editing.

Conflict of interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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