Dosimetric predictors of persistent xerostomia after IMRT for nasopharyngeal carcinoma
PO-1197
Abstract
Dosimetric predictors of persistent xerostomia after IMRT for nasopharyngeal carcinoma
Authors: Nejla Fourati1, Syrine Zouari1, Mariem Frikha1, Zied Fessi1, Wicem Siala1, Wafa Mnejja1, Jamel Daoud1
1Habib Bourguiba Hospital Faculty of Medicine University of Sfax, Radiotherapy Department, Sfax, Tunisia
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Purpose or Objective
Radiation-induced Xerostomia could impair speech, tasting, and swallowing and thus alteration of the quality of life of long survivors.
The study aimed to identify dosimetric predictors for the persistence of xerostomia in patients with nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT).
Material and Methods
This prospective study included 45 patients diagnosed with non-metastatic NPC between June 2017 and February 2020. All patients received neoadjuvant chemotherapy followed by concurrent chemoradiation according to an IMRT technique. Clinical assessment of xerostomia and measurement of salivary flow was performed at the end of the RT sessions, 1, 3, and 6 months later. Xerostomia was assessed using the Radiation Therapy Oncology Group criteria. Predictors for persistent xerostomia were analyzed using the Khi-Deux test. Receiver operating characteristic curve analysis was used to identify the most appropriate cut-off values for predicting factors.
Results
At the end of RT, all patients experienced xerostomia (29 (64.5%) were of grade ≥ 2). At the end of the follow-up (6 months), persistent grade 2 xerostomia was noted in 18/40 patients (45%). No patient maintained a G3 xerostomia.
Predictors for persistent xerostomia were mean dose (Dmean) and D50 for both parotid glands after excluding PTV volume with a cut-off of 31 Gy and 25 Gy respectively.
Table 1 shows a significant difference in xerostomia grade using these dose constraints.
Clinical factors and other dosimetric factors (Volume and Dose maximum of parotid glands, dose received by submandibular gland) were not associated with persistent xerostomia grade ≥ 2.
| Xerostomia G0-1 end of treatment | Xerostomia G2-3 end of treatment
| p | Xerostomia G0-1 end at 3 monts
| Xerostomia G2-3 end at 3 monts
| p |
Dmean 2parotids - PTV < 31Gy Dmean 2parotids - PTV ≥ 31Gy
| 56%
44% | 21%
79% | 0.019 | 36%
64% | 0%
100% | 0.036 |
D50 2parotids - PTV < 25Gy D50 2parotids - PTV ≥ 25Gy
| 69%
31% | 25%
75% | 0.005 | 44%
56% | 10%
90% | 0.11 |
Conclusion
Xerostomia represents a common problem observed after IMRT of NPC. For all head and neck cancers, a dose constraint of Dmean of <26 Gy to at least 1 parotid gland is proposed. However, this dose is hard to achieve for NPC patients given the proximity of lymphadenopathy to parotid glands. Results of our study show that Dmean <31 Gy and D50 <25 Gy could be reasonable to respect for both parotids–PTV during dosimetric optimization of NRP IMRT to decrease the rate of persistent xerostomia.