D. Verellen et F. Vanhavere, Risk assessment of radiation-induced malignancies based on whole-body equivalent dose estimates for IMRT treatment in the head and neck region, RADIOTH ONC, 53(3), 1999, pp. 199-203
Citations number
18
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Onconogenesis & Cancer Research
Background and purpose: Intensity modulated radiation therapy (IMRT) has be
en introduced in our department for treatment of the head and neck region w
ith the intention of reducing complications without compromising treatment
outcome. However, these new treatment modalities inevitably require a subst
antial increase in monitor units per target dose yielding an increased risk
of secondary malignancies induced by the treatment. This study aims at ass
essing the increased risk by means of in vivo measurements of the whole-bod
y equivalent dose of both the conventional and the IMRT treatment technique
s for head and neck lesions.
Material and methods. A conventional technique using parallel opposed, wedg
ed treatment fields has been compared with a slice-by-slice are rotation te
chnique for IMRT, Both techniques were used to treat head and neck lesions
with a 6-MV photon beam. Thermoluminescent badges and neutron bubble detect
ors designed for personnel monitoring have been applied to obtain the estim
ated whole-body equivalent dose on three patients for each treatment techni
que, The nominal probability coefficient for a lifetime risk of excess fata
l cancer, recommended by the ICRP 60 has been used for risk estimates based
on the estimated dose values.
Results: An estimated whole-body equivalent dose per monitor unit equal to
1.2 x 10(-2) mSv/MU and 1.6 x 10(-2) mSv/MU have been obtained with the con
ventional and IMRT technique, respectively. Applying the average amount of
MU necessary to realize a 70 Gy target dose the estimated whole-body equiva
lent dose for both treatment techniques becomes 242 mSv (conventional) and
1969 mSv (IMRT), yielding an increase in the risk for secondary malignancie
s with a factor 8.
Conclusions: Historically the risk of secondary malignancies has been accep
ted to take advantage of the possible benefits of improved local control an
d treatment outcome. However, the introduction of new and sophisticated tre
atment techniques will also increase the risk of radiation induced malignan
cies. Therefore, these risk estimates become important to assess whether th
e benefits of the treatment technique outweigh the possible risks. (C) 1999
Elsevier Science Ireland Ltd. All rights reserved.