Ahmidouch Manal, Das Shiva K, Zhu Tong, Shen Colette, Marks Lawrence B, Chera Bhishamjit S, Fried David V
University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Department of Radiation Oncology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
J Appl Clin Med Phys. 2024 Dec;25(12):e14515. doi: 10.1002/acm2.14515. Epub 2024 Sep 17.
The aim of this study was to identify dose constraints for the parotid ducts that limit patient-reported xerostomia and estimate whether these constraints are achieved during conventional parotid gland sparing radiation therapy (PGS-RT).
Thirty-eight oropharyngeal squamous cell carcinoma patients were treated prospectively on trial with MRI sialography-guided parotid duct sparing radiation therapy (PDS-RT). PDS-RT explicitly minimizes dose to the parotid ducts in addition to PGS-RT. Parotid duct dose constraints were identified that distinguished patients reporting high and low rates of xerostomia. Atlas-based parotid duct contours were generated on a retrospective cohort of similar patients where the parotid ducts were not contoured nor explicitly spared to estimate the dose received by the parotid ducts during PGS-RT.
Patients whose intraglandular parotid ducts or total parotid ducts were planned for a mean dose < 14 Gy and < 12 Gy, respectively, reported significantly (p < 0.01) lower rates of xerostomia at 6 and 12 months post-RT. Patients receiving PDS-RT had average total and intraglandular duct doses of 11.6 and 13.6 Gy, respectively, compared to an estimated 23.8 and 22.1 Gy, for those receiving PGS-RT (p < 0.01). Only 6% (6/108) and 20% (22/108) of patients receiving PGS-RT were estimated to meet the dose constraints for the total ducts and intraglandular ducts, respectively.
Parotid duct dose thresholds exist that appear to distinguish patients with and without xerostomia. The identified dose thresholds are frequently not met in PGS-RT plans. In addition to reducing the dose to the parotid gland(s), parotid duct sparing may also further reduce xerostomia.
本研究旨在确定腮腺导管的剂量限制，以限制患者报告的口干症，并评估在传统的腮腺保留放疗（PGS-RT）过程中是否能达到这些限制。
38例口咽鳞状细胞癌患者前瞻性地接受了MRI涎管造影引导下的腮腺导管保留放疗（PDS-RT）试验。除PGS-RT外，PDS-RT还明确将腮腺导管的剂量降至最低。确定了区分口干症发生率高和低的患者的腮腺导管剂量限制。在一组类似患者的回顾性队列中生成基于图谱的腮腺导管轮廓，这些患者的腮腺导管未进行轮廓勾画也未明确保留，以估计PGS-RT期间腮腺导管接受的剂量。
分别计划腺内腮腺导管或总腮腺导管平均剂量<14 Gy和<12 Gy的患者，在放疗后6个月和12个月报告的口干症发生率显著较低（p<0.01）。接受PDS-RT的患者总导管和腺内导管的平均剂量分别为11.6 Gy和13.6 Gy，而接受PGS-RT的患者估计平均剂量为23.8 Gy和22.1 Gy（p<0.01）。估计接受PGS-RT的患者中分别只有6%（6/108）和20%（22/108）符合总导管和腺内导管的剂量限制。
存在腮腺导管剂量阈值，似乎可以区分有无口干症的患者。在PGS-RT计划中，确定的剂量阈值常常无法达到。除了降低腮腺的剂量外，保留腮腺导管也可能进一步减少口干症。
