Clivio Alessandro, Zwahlen Daniel R, Koch Sonja, Negreanu Cezarina, Barletta Enrico, Haerle Helmut, Hofmann Elena, Oehler Christoph
Zentrum für Radiotherapie Rüti Zürich-Ost-Linth AG, Rüti, ZH, Switzerland.
Department of Radiation Oncology, Hospital Winterthur, Winterthur, Switzerland.
Strahlenther Onkol. 2025 Jun;201(6):589-600. doi: 10.1007/s00066-024-02321-8. Epub 2024 Nov 25.
Hypothyroidism affects up to 21% of women with breast cancer after supraclavicular node irradiation. The PENTEC (pediatric normal tissue effects in the clinic) initiative highlighted the need to minimize the thyroid dose, albeit without giving a specific constraint. This study aimed to define a reasonable target thyroid mean dose (D) between 10 and 15 Gy using intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) and examine its impact on the hypothyroidism risk.
Forty-three breast cancer patients with supraclavicular irradiation neglecting the thyroid in terms of dose protection were included from 01/2020 to 04/2021. An IMRT or VMAT technique was used in 23 and 20 patients, respectively. Replanning aimed for a thyroid D of 10 Gy. IMRT plans still exceeding 10 Gy were converted into VMAT plans. Fisher's sign test compared original and revised plans and the hypothyroidism risk was calculated.
Initial radiotherapy plans had a thyroid D of 18.4 ± 7.9 Gy (IMRT: 20.4 ± 8.8 Gy, VMAT: 16.2 ± 6.2 Gy). Replanning significantly reduced D to 10.3 ± 4.5 Gy (-44%) overall (IMRT: -50%, VMAT: -35%), with 56% achieving ≤ 10 Gy (IMRT: 33.3%, VMAT: 61%). Furthermore, an IMRT to VMAT conversion yielded a thyroid D of 9.2 ± 3.5 Gy, with 74.4% of patients ≤ 10 Gy, albeit at the cost of higher doses to the contralateral breast. Clinical and planning target volume (CTV/PTV) coverage remained uncompromised. The calculated hypothyroidism risk significantly decreased from 24.5% to 13.3% (D = 10 Gy) or 16.3% (D = 13.5 Gy).
Implementing a thyroid organ at risk (OAR) constraint D of 13.5 Gy was feasible in 88% of patients without compromising other OARs and CTV/PTV coverage, and resulted in a 33-46% reduction of the hypothyroidism risk.
Retrospectively registered.
锁骨上淋巴结照射后，高达21%的乳腺癌女性会出现甲状腺功能减退。PENTEC（临床小儿正常组织效应）倡议强调了尽量减少甲状腺剂量的必要性，尽管没有给出具体限制。本研究旨在使用调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）确定10至15 Gy之间合理的甲状腺平均剂量目标（D），并研究其对甲状腺功能减退风险的影响。
纳入2020年1月至2021年4月期间43例在剂量保护方面未考虑甲状腺的接受锁骨上照射的乳腺癌患者。分别有23例和20例患者使用了IMRT或VMAT技术。重新规划的目标是甲状腺D为10 Gy。仍超过10 Gy的IMRT计划被转换为VMAT计划。采用Fisher符号检验比较原始计划和修订计划，并计算甲状腺功能减退风险。
初始放射治疗计划的甲状腺D为18.4±7.9 Gy（IMRT：20.4±8.8 Gy，VMAT：16.2±6.2 Gy）。重新规划后总体上显著将D降低至10.3±4.5 Gy（-44%）（IMRT：-50%，VMAT：-35%），56%的患者达到≤10 Gy（IMRT：33.3%，VMAT：61%）。此外，从IMRT转换为VMAT后甲状腺D为9.2±3.5 Gy，74.4%的患者≤10 Gy，尽管对侧乳腺剂量更高。临床靶区和计划靶区（CTV/PTV）的覆盖不受影响。计算出的甲状腺功能减退风险从24.5%显著降至13.3%（D = 10 Gy）或16.3%（D = 13.5 Gy）。
对88%的患者实施13.5 Gy的甲状腺危及器官（OAR）剂量限制是可行的，且不影响其他OAR以及CTV/PTV的覆盖，并使甲状腺功能减退风险降低33%至46%。
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