Radiation therapy is well tolerated in general. Treatment itself is not painful, however there are side effects. The risk of side effects is depends on several aspects of the treatment and it is approached individually in every patient.

Side effects with radiation therapy of the nasal cavity:

Early side effects:

• Occur almost always with a definitive radiation therapy. They are observed typically after 2 weeks of treatment and they can peak until a week after the treatment. After that they tend to resolve
• Most of the time they are manageable and resolve with time
• We can observe inflammation of the nasal and/or oral mucosa
• Dermatitis of the muzzle
• Conjunctivitis, uveitis, blepharitis, KCS
• Rarely neurological signs, if a significant portion of brain is in radiation field 

Late side effects:

• They are rare in general and occur more frequently with palliative protocols
• Time of occurrence is typically a year after (minimum 6 months)
• Usually irreversible
• They can involve bone necrosis, brain necrosis, glaucoma, chronic rhinitis 

Side effects with radiation therapy of the brain:

Early side effects:

• Occur almost always with a definitive radiation therapy. They are observed typically after 2 weeks of treatment and they can peak until a week after the treatment. After that they tend to resolve
•  Most of the time they are manageable and resolve with time
• They can be non-specific but can also present as neurological signs such as seizures
• Depending on the mass location an inflammation of the pharynx and/or otitis

Early delayed side effects:

• Typically 3 months after the treatment
• Result from inflammation of the brain tissue
• Clinical signs are usually mild but can involve seizures which resolve with steroid administration

Late side effects:

• They are rare in general and occur more frequently with palliative protocols
• Time of occurrence is typically a year after (minimum 6 months)
• Usually irreversible
• Result from brain necrosis and can manifest as refractory seizures or other neurological signs 
• The risk of late side effects is minimised by using definitive protocols