Dose distribution in the thyroid gland following radiation therapy of breast cancer-a retrospective study
Type
Peer reviewed; Journal articlePeer reviewed
publishedVersion
Date
2011-06-09
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Show full item recordAbstract
Purpose: To relate the development of post-treatment hypothyroidism with the dose distribution within the
thyroid gland in breast cancer (BC) patients treated with loco-regional radiotherapy (RT).
Methods and materials: In two groups of BC patients postoperatively irradiated by computer tomography (CT)-
based RT, the individual dose distributions in the thyroid gland were compared with each other; Cases developed
post-treatment hypothyroidism after multimodal treatment including 4-field RT technique. Matched patients in
Controls remained free for hypothyroidism. Based on each patient’s dose volume histogram (DVH) the volume
percentages of the thyroid absorbing respectively 20, 30, 40 and 50 Gy were then estimated (V20, V30, V40 and
V50) together with the individual mean thyroid dose over the whole gland (MeanTotGy). The mean and median
thyroid dose for the included patients was about 30 Gy, subsequently the total volume of the thyroid gland
(VolTotGy) and the absolute volumes (cm3) receiving respectively < 30 Gy and ≥ 30 Gy were calculated (Vol < 30
and Vol ≥ 30) and analyzed.
Results: No statistically significant inter-group differences were found between V20, V30, V40 and V50Gy or the
median of MeanTotGy. The median VolTotGy in Controls was 2.3 times above VolTotGy in Cases (r = 0.003), with
large inter-individual variations in both groups. The volume of the thyroid gland receiving < 30 Gy in Controls was
almost 2.5 times greater than the comparable figure in Cases.
Conclusions: We concluded that in patients with small thyroid glands after loco-radiotherapy of BC, the risk of
post-treatment hypothyroidism depends on the volume of the thyroid gland.
Citation
Radiation Oncology 2011, 6:68Publisher
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Copyright 2011 Johansen et al; licensee BioMed Central Ltd.