A longitudinal evaluation of early anatomical changes of parotid gland in intensity modulated radiotherapy of nasopharyngeal carcinoma patients with parapharyngeal space involvement

BackgroundXerostomia is one of the most common adverse events of radiotherapy in head and neck cancer patients. There have been many reports on functional changes of the parotid gland after radiation therapy, but there have been few reports on the volume of the parotid gland and its relationship with oral quality of life (QOL) and even fewer reports on longitudinal change of the parotid gland volume. The purpose of this study was to evaluate the long-term change of the parotid gland volume after intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma and the relationship between parotid irradiation dose and xerostomia symptoms.MethodsWe retrospectively analyzed 26 patients with nasopharyngeal cancer treated by IMRT. Longitudinal changes of parotid gland volumes after IMRT were evaluated on CT images. The parotid gland volumes in each period were converted to the ratio to parotid gland volumes before radiotherapy (relative parotid volume). Dunnett’s test was used to evaluate the longitudinal changes in relative parotid volumes at 0-6, 7-18, 19-30, 31-42, 43-54 and 55-66 months after IMRT. We assessed xerostomia 3 years or more after IMRT by measuring the degree of oral moisture using a moisture-checking device (Mucus, Life Co., Ltd.) and oral QOL evaluation by GOHAI (General Oral Health Assessment Index).ResultsThe relative parotid volumes during radiotherapy and at 0-6, 7-18, 19-30, 31-42, 43-54 and 55-66 months after IMRT were 75.2 ± 14.3%, 67.2 ± 11.4%, 68.5 ± 15.9%, 72.4 ± 14.8%, 73.0 ± 13.8%, 76.2 ± 17.5%, and 77.1% ± 17.3%, respectively. The parotid volume had recovered significantly at 43-54 and 55-66 months after IMRT, especially in parotids receiving less than 40 Gy as the mean dose. The mean irradiated dose for bilateral parotids showed negative correlations with oral QOL score and oral moisture after a long period.ConclusionsThe parotid volume recovered gradually but had not reached a plateau even 3 years after radiotherapy, especially in parotids receiving less than 40 Gy as the mean dose.

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Individualized Clinical Target Volume Delineation and Efficacy Analysis in Unilateral Nasopharyngeal Carcinoma Treated with Intensity-Modulated Radiotherapy (IMRT): 10-Year Summary and Results

10.21203/rs.3.rs-938329/v1 ◽

2021 ◽

Author(s):

De-Huan Xie ◽

Zheng Wu ◽

Wang-Zhong Li ◽

Wan-Qin Cheng ◽

Ya-Lan Tao ◽

...

Keyword(s):

Nasopharyngeal Carcinoma ◽

Clinical Target Volume ◽

Parapharyngeal Space ◽

Intensity Modulated Radiotherapy ◽

Target Volume ◽

Recurrence Free Survival ◽

Free Survival ◽

Intensity Modulated

Abstract Purpose: To evaluate the long-term local control, failure patterns, and toxicities after individualized clinical target volume (CTV) delineation in unilateral nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT).Methods: Unilateral NPC was defined as nasopharyngeal mass confined to one side of nasopharynx and did not significantly exceed the midline of nasopharyngeal apex/posterior wall. From November 2003 to December 2017, 95 patients with long-term follow-up were retrospectively included. All patients received IMRT. The CTVs were determined based on the distance from the gross tumor, the contralateral parapharyngeal space and skull base orifices were spared from irradiation.Results: There were 3 local recurrence and 8 regional recurrences in 10 patients during 84- month follow-up. All local recurrences were PGTVnx-in-field, and no recurrences in traditional high-risk area including contralateral parapharyngeal space and skull base orifices. The 10-year local-recurrence free survival, regional-recurrence free survival and overall survival were 96.2%, 90.5% and 84.7%, respectively. The dosimetry parameters of the tumor-contralateral organs were all lower than the values of the tumor-ipsilateral side (P < 0.05). The late toxicities occurred mainly in the tumor-ipsilateral organs, including radiation-induced temporal lobe injury, impaired visuality, hearing loss and subcutaneous fibrosis.Conclusion: Individualized CTV delineation in unilateral NPC could yield excellent long-term local control with limited out-of-field recurrences, reduced dose to tumor- contralateral organs and mild late toxicities, which is worthy of further exploration.

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