Hypothyroidism as a consequence of intensity-modulated radiotherapy with concurrent taxane-based chemotherapy for locally advanced head-and-neck cancer.
OBJECTIVE
To conduct a retrospective review of 168 consecutively treated locally advanced head-and-neck cancer (LAHNC) patients treated with intensity-modulated radiotherapy (IMRT)/chemotherapy, to determine the rate and risk factors for developing hypothyroidism.


METHODS
Intensity-modulated radiotherapy was delivered in 33 daily fractions to 69.3 Gy to gross disease and 56.1 Gy to clinically normal cervical nodes. Dose-volume histograms (DVHs) of IMRT plans were used to determine radiation dose to thyroid and were compared with DVHs using conventional three-dimensional radiotherapy (3D-RT) in 10 of these same patients randomly selected for replanning and with DVHs of 16 patients in whom the thyroid was intentionally avoided during IMRT. Weekly paclitaxel (30 mg/m(2)) and carboplatin area under the curve-1 were given concurrently with IMRT.


RESULTS
Sixty-one of 128 evaluable patients (47.7%) developed hypothyroidism after a median of 1.08 years after IMRT (range, 2.4 months to 3.9 years). Age and volume of irradiated thyroid were associated with hypothyroidism development after IMRT. Compared with 3D-RT, IMRT with no thyroid dose constraints resulted in significantly higher minimum, maximum, and median dose (p < 0.0001) and percentage thyroid volume receiving 10, 20, and 60 Gy (p < 0.05). Compared with 3D-RT, IMRT with thyroid dose constraints resulted in lower median dose and percentage thyroid volume receiving 30, 40, and 50 Gy (p < 0.005) but higher minimum and maximum dose (p < 0.005).


CONCLUSIONS
If not protected, IMRT for LAHNC can result in higher radiation to the thyroid than with conventional 3D-RT. Techniques to reduce dose and volume of radiation to thyroid tissue with IMRT are achievable and recommended.
Diaz
Roberto
R
Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
Jaboin
Jerry J
JJ
Morales-Paliza
Manuel
M
Koehler
Elizabeth
E
Phillips
John G
JG
Stinson
Scott
S
Gilbert
Jill
J
Chung
Christine H
CH
Murphy
Barbara A
BA
Yarbrough
Wendell G
WG
Murphy
Patrick B
PB
Shyr
Yu
Y
Cmelak
Anthony J
AJ
D000367:Age Factors; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001952:Bridged-Ring Compounds / Q000008:administration & dosage; D016190:Carboplatin / Q000008:administration & dosage; D003131:Combined Modality Therapy / Q000009:adverse effects / Q000379:methods; D019583:Dose Fractionation, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007037:Hypothyroidism / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D017239:Paclitaxel / Q000008:administration & dosage; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D043823:Taxoids / Q000008:administration & dosage; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000187:drug effects / Q000528:radiation effects*
D001952:Bridged-Ring Compounds; D043823:Taxoids; C080625:taxane; D016190:Carboplatin; D017239:Paclitaxel