paediatrics Brussels 17

Radiotherapy Late Effects

Organ/Tissue

Dose Threshold

Late Toxicity

Central Nervous System

~ 18 Gy

Neuropsychological damage, reduced IQ, learning and behaviour difficulties

Pituitary

~ 18 Gy for impaired GH secretion, higher threshold (~ 40 Gy) for other hormones

Multiple hormone deficiencies, particularly growth hormone (GH), also adreno-cortico trophic hormone (ACTH) and thyroid stimulating hormone (TSH)

Thyroid

20 Gy

Reduced thyroid hormone secretion

Gonads

1-2 Gy (testes), 6-10 Gy (ovaries)

Infertility if irradiation of the testes or ovaries cannot be avoided

Bone

Threshold ~ 10 Gy fractionated RT Worst in young children treated with > 20 Gy

Impaired bone growth, and associated impairment of soft tissue development. This is particularly severe in the facial, head and neck regions

Kidney

12-15 Gy

Hypertension, reduced renal function

Dentition

~ 4-10 Gy

Dental caries, impaired dental development and mal- development of jaw

Eye

~ 10 Gy (Cataract), ~ 25 Gy Dry eye

Cataract, dry eye

Second (radiation induced) malignancy

Low threshold for adenocarcinomas, e.g. breast, thyroid. High threshold for sarcomas

e.g. breast and thyroid cancers after RT for Hodgkin ’ s Disease, Sarcomas after RT for many cancers, including brain tumours