Upasani Maheshkumar N, Shinde Prashantkumar, Veer Rameshwar
Department of Radiation Oncology, National Cancer Institute, Nagpur, India.
Department of Medical Physics, National Cancer Institute, Nagpur, India.
Support Care Cancer. 2024 Dec 12;33(1):21. doi: 10.1007/s00520-024-09058-1.
Palliative whole-brain radiotherapy (WBRT) is a useful treatment modality for patients diagnosed with brain metastasis. Our study aimed to document parotid doses using a short course of 20 Gy in five fractions (SC-WBRT) and compare them with the known xerostomia parameters.
We retrieved dosimetric parameters for 59 patients who received SC-WBRT. The contouring of parotids was done retrospectively. The data was stratified depending on the lower edge of the planning target volume (PTV) border, up to either the first cervical vertebra (C1) or the second cervical vertebra (C2). The biologically effective dose (BED) of the parotid dose constraints from the literature was calculated and corrected to obtain the dose for a five-fraction treatment. These were used as a reference for assessing the parotid doses of our cohort.
With SC-WBRT, the mean doses of either gland (11.46 Gy) and of total parotids (11.48 Gy) were statistically significantly less than the BED corrected constraints of 12.82 Gy (p < 0.01) and 15.31 Gy (p < 0.01). Patients with PTV to C1, compared to those with a PTV to C2, had significantly lower mean doses of either gland (9.44 Gy vs 12.76 Gy, p < 0.01) and total parotid dose (9.44 Gy vs 12.78 Gy, p < 0.01). Patients with PTV to C1 had doses significantly lower than all the reference dose parameters.
Routine delineation and documentation of parotid dosimetry would enable parotid sparing, irrespective of the dose regimen used. SC-WBRT provides better parotid sparing dosimetrically which may reduce the related toxicities even in palliative settings. Limiting the lower border of the PTV to C1 will further decrease the parotid doses.
姑息性全脑放疗（WBRT）是诊断为脑转移患者的一种有效治疗方式。我们的研究旨在记录采用20 Gy分5次的短疗程（SC-WBRT）时腮腺的剂量，并将其与已知的口干症参数进行比较。
我们检索了59例接受SC-WBRT患者的剂量学参数。腮腺的轮廓勾画是回顾性进行的。数据根据计划靶体积（PTV）边界的下缘进行分层，直至第一颈椎（C1）或第二颈椎（C2）。计算并校正了文献中腮腺剂量限制的生物等效剂量（BED），以获得5次治疗的剂量。这些用作评估我们队列腮腺剂量的参考。
采用SC-WBRT时，任一腺体的平均剂量（11.46 Gy）和腮腺总体平均剂量（11.48 Gy）在统计学上均显著低于校正后的BED限制剂量12.82 Gy（p < 0.01）和15.31 Gy（p < 0.01）。PTV下缘至C1的患者与PTV下缘至C2的患者相比，任一腺体的平均剂量显著更低（9.44 Gy对12.76 Gy，p < 0.01），腮腺总剂量也显著更低（9.44 Gy对12.78 Gy，p < 0.01）。PTV下缘至C1的患者的剂量显著低于所有参考剂量参数。
腮腺剂量学的常规勾画和记录将有助于腮腺保护，无论使用何种剂量方案。SC-WBRT在剂量学上能更好地保护腮腺，即使在姑息治疗情况下也可能降低相关毒性。将PTV的下缘限制在C1将进一步降低腮腺剂量。
