The shrinking thyroid: how does thyroid size change following radiation therapy for laryngeal cancer?
OBJECTIVE
External beam radiation therapy (XRT) for head and neck cancer is known to induce hypothyroidism and cause morphologic changes in the thyroid gland. This retrospective study investigates change in the size of the thyroid gland detectable by CT after XRT for laryngeal cancer.


METHODS
The measured width of the thyroid lobes in 61 patients treated nonsurgically with XRT for laryngeal cancer between 2000 and 2003 on posttherapy CT was compared with that on pretherapy CT. Absolute and percentage changes in measured thyroid width following XRT were analyzed according to chemotherapy administration and posttherapy thyroid function.


RESULTS
Eighty-five percent (52/61) of patients had a decrease in the width of the thyroid gland. The average change in width measuring -4.7 mm and -13.8% (SD, 5.7 mm and 19.9%) occurred at an average of 758 days following completion of XRT (mean, 402-1534 days) and was significant (P = .002). Average change in width between hypothyroid patients (n = 19, -6.1 mm and -20.0% change) and euthyroid patients (n = 42, -4.1 mm and -11.1% change) was not significant (P = .20 absolute change and P = .11 percentage change). The average change in width between patients receiving chemotherapy (n = 31, -5.5 mm and -16.1% change) and patients not receiving chemotherapy (n = 30, -3.9 mm and -11.5% change) was not significant (P = .26 absolute change and P = .37 for percentage change).


CONCLUSIONS
Most nonsurgical patients receiving XRT for laryngeal cancer have a significant decrease in the width of their thyroid glands detected on CT. The average change in the size of the thyroid gland does not differ when development of hypothyroidism or chemotherapy administration are considered.
Miller-Thomas
M M
MM
Division of Diagnostic Imaging, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA. thomasm@mir.wustl.edu
Kumar
A J
AJ
Sellin
R V
RV
Azimpoor
S
S
Ang
K K
KK
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002276:Carcinoid Tumor / Q000188:drug therapy / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D007822:Laryngeal Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D008875:Middle Aged; D009929:Organ Size / Q000528:radiation effects; D011878:Radiotherapy / Q000009:adverse effects*; D012189:Retrospective Studies; D012208:Rhabdomyosarcoma / Q000188:drug therapy / Q000532:radiotherapy; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000473:pathology* / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
D000970:Antineoplastic Agents