Intratumoral injection of radioactive holmium ( 166 Ho) microspheres for treatment of oral squamous cell carcinoma in cats.

BACKGROUND & AIMS: A "microbrachytherapy" was developed as treatment option for inoperable tumours by direct intratumoral injection of radioactive holmium-166 ( 166 Ho) microspheres (MS). 166 Ho emits β-radiation which potentially enables a high, ablative, radioactive-absorbed dose on the tumour tissue while sparing surrounding tissues.

MATERIALS &

METHODS

Safety and efficacy of 166 Ho microbrachytherapy were evaluated in a prospective cohort study of 13 cats with inoperable oral squamous cell carcinoma without evidence of distant metastasis.

RESULTS

Local response rate was 55%, including complete response or partial response (downstaging) enabling subsequent marginal resection. Median survival time was 113 days overall, and 296 days for patients with local response. Side effects were minimal. Tumour volume was a significant predictor of response.

DISCUSSION: Response rate may be further improved by optimizing the intratumoral spatial distribution of 166 Ho MS.

CONCLUSION

166 Ho microbrachytherapy has potential as a minimally invasive, single procedure radio-ablation treatment of unresectable tumours with minimal morbidity.