Long-term follow-up data are limited but animal studies suggest that IORT exposures up to 30 Gy carry little risk of long-term sequelae as long as sensitive structures such as major nerves, blood vessels, the spinal cord, or the small bowel are kept out of the irradiation field. The threshold for nerve damage is 20-25 Gy with a latent period of 6-9 months with little damage seen below 10-15 Gy in large animal models.
A further factor to be considered is late malignancy—a number of studies in dogs have reported a high incidence of sarcomas induced by IORT compared to other treatment modalities. Issues such as treatment planning are clearly complex, as only limited advanced data can be available.2
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