| Objective:The purpose of this study was to analyse the influencing factors of xerostomia with nasopharyngeal carcinoma( NPC) patients after intensity-modulated radiation therapy( IMRT), to investigate the correlation between radiation dosimetry of parotid and submandibular gland with xerostomia. To provide an alternative measure for clinicians to predict and evaluate the extent of the xerostomia, so that appling a reference dosimetry to reduce the incidence and severity of xerostomia of the patients with nasopharyngeal carcinoma after radiotherapy.Methods:284 patients who were primarily diagnosed as nasopharyngeal carcinoma and treated by IMRT were enrolled in this study in the Fujian Provincial Cancer Hospital from January, 2010 to December, 2011. Various measuring scales were used in the investigation,which included EORTC QLQ-C30(version3.0)and self-designed questionnaire that was about basic information of patients. These investigations were conducted within 48 hours after admission and six months after the radiation and chemotherapy respectively. The data including V25,V30,V40,D50,Dmean and Dmax of parotid and submandibular gland were collected through the dosed volume histogram(DVH). Univariate and multivariate Ordinal Logistic regression were used to analyze the influencing factors of xerostomia post-radiotherapy. Variables with P≤0.05 in univariate analysis were included in multivariate analysis, and P≤0.05 was considered statistically significant. ROC curve was used to obtain the best diagnosis critical point of the factors related to xerostomia at the end of radiotherapy. Used the canonical discriminant preliminary to establish the forecast model of radioactive xerostomia.Results:The incidence of the group of no xerostomia and xerostomia was 33.45% and 66.55%,respectively in 284 patients. Univariate analysis showed that Dmean( P< 0.001),Dmax( P=0.045)and D50( P< 0.001),V25( P=0.016),V30( P=0.013),V40( P=0.002)of submandibular gland,Dmean( P< 0.001),V25( P=0.016),V30( P =0.004),V40( P=0.001) of parotid were related to the xerostomia after radiotherapy. Multivariate ordinal logistic regression analysis showed that Dmean of submandibular gland( P< 0.001), Dmax of submandibular gland( P=0.002),Dmean of parotid( P< 0.001),V30 of parotid(P=0.002) were related to the xerostomia after Radiotherapy. The best diagnosis critical point of Dmean and Dmax of submandibular gland, Dmean and V30 of parotid obtained was 5557.25 c GY、6427.30 c GY、3309.65 c GY、0.45,respectively for xerostomia after radiotherapy,Obtained from ROC curve, and the area under the curve was 0.702、0.488、0.782、0.651,respectively. To compare with the ROC curve of Az = 0.5 obtained by completely random cases, the significant factors were Dmean of submandibular gland,Dmean of parotid gland and V30 of parotid. Dmean of submandibular gland and Dmean of parotid gland were moderate accuracy when diagnosis xerostomia and V30 of parotid was low. Set Dmean of submandibular gland for X1, Dmean of parotid for X2, canonical discriminant,obtain canonical discriminant function: Y = 8.701 + 0.001 X1 + 0.001X2, the possibility of xerostomia of individual cases is small when the Y value is less than 3.24.and more likely to be xerostomia when the Y value is more than 3.24.The discriminant accuracy of the discriminant equation is 75.0%( be well up to the average).Conclusion:Dmean and Dmax of submandibular gland,Dmean and V30 of parotid were related to the xerostomia after Radiotherapy. Dmean of submandibular gland and Dmean of parotid gland were moderate accuracy when diagnosis xerostomia but V30 of parotid was low.The best diagnosis critical point of Dmean of submandibular gland and Dmean of parotid gland were 5557.25 c GY and 3309.65 c GY. Set Dmean of submandibular gland for X1,Dmean of parotid for X2, in the canonical discriminant function: Y = 8.701 + 0.001X1 + 0.001X2, the possibility of xerostomia is small when the Y value is less than 3.24.and more likely to be xerostomia when the Y value is more than 3.24. |
PDF Full Text Request