Effects Of Radiotherapy On Parotid Volume Of Nasopharyngeal Carcinnoma Patients And The Correlation Of The Degree Of Xerostomia

Objective: To observe the intensity modulated radiation therapy(IMRT) in patients with nasopharyngeal carcinoma, radiotherapy over, after radiotherapy 1 months, 3 months of bilateral parotid gland size changes, and the change of the degree of dry mouth, contrast at all time points, patients with bilateral parotid gland atrophy degree and degree of dry mouth, and then study nasopharyngeal carcinoma after radiotherapy in patients with parotid gland atrophy degree change, dry mouth restoration degree and parotid gland illuminated dose, the relationship between the switch and strong radiation therapy play a guiding role in the treatment of patients with nasopharyngeal carcinoma.Methods: This study selected the patients who were in June 2014 to January 2016 Jilin University China Japan Union Hospital accept intensity-modulated radiotherapy of nasopharyngeal carcinoma radiotherapy of hospital patients with 37 cases. Locate scan sketch target enhancement CT simulation and endanger organs, evaluate the bilateral parotid illuminated dose, before radiation therapy, radiation therapy, radiation therapy after one month and three months after radiotherapy for head and neck mri examination in order to record the change of the parotid gland volume, and follow-up of patients with questionnaires was graded the degree of dry mouth and record.Results: before radiotherapy, of parotid gland volume with an average of 24.14±7.19cm3, after the contralateral parotid gland volume with an average of 22.67±6.49 cm3; At the end of radiotherapy of parotid gland volume averaged 17.48±6.32 cm3, after the contralateral parotid gland volume with an average of 17.72±5.98 cm3; One month after radiotherapy of parotid gland volume with an average of 16.58±6.71 cm3, after the contralateral parotid gland volume with an average of 16.23 ±7.44 cm3 after; 3 months after radiotherapy of parotid gland volume with an average of 15.53±6.31 cm3, after the contralateral parotid gland volume with an average of 15.87±6.17 cm3 after. Grouping is at the end of radiotherapy, one month and three months after radiotherapy, relations with volume rate, mean dose of parotid gland with bilateral parotid average dose greater than 30 Gy group at all time points of the parotid gland volume change rate were greater than other groups, and at all time difference was statistically significant(P< 0.05); While the contralateral parotid average dose and volume change rate at all time points of difference has no statistical significance(P>0.05). Contrast middle-late stage(Ⅲstage and Ⅳ stage) patients and patients with early stage(Ⅰ stage and Ⅱstage) patients with parotid gland volume shrinking degree at all time points when the difference had statistical significance(P< 0.05). According to RTOG dry mouth classification standard evaluation: all cases with no xerostomia before radiotherapy, radiation at the end of the 1st level dry mouth 4 cases(10.81%), 2 levels of 14 cases(37.83%),xerostomia level 3 dry mouth 19 cases(51.33%). 3 months after radiotherapy,xerostomia 1 class 4 cases(10.81%), 2 levels of 14 cases(37.83%),xerostomia level 3 is 19 cases(51.33%). Within three months after radiotherapy, greater than the mean dose of parotid gland in more than 30 gy patients with moderately severe( 2 ~ 3level) xerostomia, and the mean dose of parotid gland is less than 30 Gy more patients in mild-to-moderate( 1 ~ 2 level) xerostomia. Patients with xerostomia better group(24.82 ± 7.10 Gy) mean dose of the healthy side of parotid gland and parotid gland volume change rate(21.82 ± 6.23 %), average dose of(24.39 ± 7.57 Gy) of parotid gland and parotid gland volume change rate(23.64 ± 5.39 %), group were significantly less than xerostomia, no change of the contralateral parotid average dose of(31.67 ± 9.67 Gy)and parotid gland volume change rate(27.42 ± 8.11%), average dose of(34.49 ± 10.71 Gy)of parotid gland and parotid gland volume change rate(35.81 ± 9.81 %), the difference was statistically significant(P< 0.05).Conclusion: 1, at the end of the intensity modulated radiation therapy(IMRT) in patients with nasopharyngeal carcinoma(NPC), bilateral parotid gland volume compared to before radiotherapy significantly narrowed, degree of the variation of parotid gland is more apparent. With bilateral parotid average dose greater than 30 Gy group at the end of the radiation therapy, radiation therapy, after 1 month and 3 months of parotid gland volume change rate were greater than other dose groups, within 3 months after radiotherapy and extension of the parotid gland volume narrowed over time. 2, intensity modulated radiation therapy(IMRT) in patients with nasopharyngeal carcinoma of parotid gland volume change associated with the installment, the bigger the mean dose of parotid gland and its degree of dry mouth, the more difficult to recover. And dry mouth recovery and parotid gland volume change rate may be related. 3, intensity modulated radiation treatment planning, parotid gland average illuminated dose should be strictly controlled under tolerance.