Radiotherapeutic factors affecting the incidence of developing hypothyroidism after radiotherapy for head and neck squamous cell cancer

الملخص EN

Purpose : The purpose of this study is to determine radiotherapy (RT) dose-volumetric threshold of radiation-induced hypothyroidism (HT) in head and neck squamous cell carcinoma (HNSCC) patients.

Patients and methods : The diagnosis of HT in 78 HNSCC patients treated with RT was based on a thyroid stimulating hormone (TSH) level greater than the maximum value of laboratory range.

In all patients, dose-volumetric parameters were analyzed according to their relation to development of HT, and thyroid volumes spared from doses 10, 20, 30, 40 and 50 Gy (V10, V20, V30, V40 and V50) were analyzed from the dose volume histograms (DVHs).

Results : Median follow-up duration was 31 months.

At the end of study, 33 patients (42.3%) developed HT and the cumulative incidence of HT was 24.6%, 36.5% and 42.3% at one, two and three years, respectively.

V30 of 42.1% (P = 0.005) was defined as dose-volumetric threshold of radiation-induced HT in HNSCC patients.

Our analysis showed that V30 separates patients into low- and high-risk groups; the incidence of radiation-induced HT in the group with V30 < 42.1% and V30 42.1% was 29.4% and 71.4%, respectively (P = 0.002).

Conclusions: The V30 may predict risk of developing HT after RT for HNSCC patients.

V30 of 42.1%, defined as dose-volumetric threshold of radiation-induced HT, can be useful in treatment planning of HNSCC patients