New radiation techniques
The potential for RT to increase the late effects of treatment is
particularly important in AYAs in whom ES is treated with curative
intent. Modern RT techniques, image guided RT, intensity modulated
photon radiotherapy (IMRT) and particle beam therapy such as proton beam
therapy (PBT), deliver improved conformal RT to the target while
reducing the volume of normal tissue that receive damaging doses of RT.
As a result of the physical characteristics of PBT, significantly less
whole-body dose is delivered compared to IMRT, reducing low as well as
high doses outside the target (Fig. 2). This may reduce late effects of
RT as well as the risk of radiation-induced malignancies and this
dosimetric benefit has been sufficient to introduce PBT as the
preferential radiation modality in the treatment of many pediatric and
AYA cancers.112-115 Data on outcomes for these
techniques in ES is limited but PBT was well tolerated by a small series
of children with ES with a low incidence of significant
toxicity.116
The risk of ovarian dysfunction from pelvic RT pelvis increases with
radiation dose. 117-119 PBT avoids significant dose to
at least one of the ovaries potentially reducing the risk of infertility
and premature menopause.151 Surgical transposition or
translocation may be used to move one or both ovaries away from the RT
target if indicated.120
Modern RT techniques also facilitate dose escalation, both in ES at
challenging sites (head and neck, pelvis and spine) and in the more
radioresistant OS that require high RT doses.83,121PBT to treat OS, alone or in combination with photons to a mean dose of
68.4Gy, resulted in a 5 year LC rate of 72%.81Internal fixation with carbon fibre and PEEK, particularly along the
spinal axis, is encouraged to improve the homogeneity and reliable
delivery of RT at these sites.122