Patients
A total of 262 patients with newly diagnosed nasopharyngeal carcinoma were enrolled in the Cancer Center of the First Affiliated Hospital of University of South China, Hengyang City, Hunan Province,China, from January 2014 to December 2018. All patients were required to meet the following conditions: histopathological diagnosis of NPC; complete the whole process of IMRT without interruption; receive intensity-modulated radiotherapy combined with concurrent chemotherapy; no distant metastasis; KPS(Karnofsky Performance Status) of more than 70 points; no other sites of tumors; patients with oral mucosal diseases before radiotherapy were excluded according to the case data. The study was approved by the institutional ethics committee.
Variables
Patient data were collected from the electronic medical record system, and selected variables included age, gender, body mass index(BMI), smoking, diabetes, clinical stage.In this study, the hematological parameters of patients before radiotherapy were collected, including leukocyte count,erythrocyte count,hemoglobin level,platelet count,lymphocyte count, neutrophil count.The study also collected planning gross target volume(PGTV), planning clinical target volume 1(PCTV1), planning clinical target volume 2(PCTV2), induction chemotherapy, and the concurrent chemotherapy interval (weekly or three-weekly chemotherapy ), and chemotherapeutic drugs (single cisplatin or single lobaplatin or docetaxel plus cisplatin regimen) .
Radiotherapy
All patients were treated with 6-MV photon IMRT using a Varian23EX, 600C/D linear accelerator, and 120 motorized gratings in the United States to complete IMRT. The patient was placed in supine position, hands were placed on the side of the body. The head, neck and shoulder were fixed with thermoplastic film. All patients were positioned using the Computer Tomography (CT) simulator of General Electric Company(GE). The scanning range was from the top of the head to 1 cm below the clavicular head, the scanning slice thickness was 3 mm, and the slice distance was 3 mm. After scanning, the CT image was transmitted to the Eclipse treatment planning system. The physician in charge delineated the target area and organs at risk layer by layer based on the definition in documents 50 and 62 of the International Radiation Unit and Measurement Committee[10, 11]and determined the dose to the tumor target area and the tolerated dose to the surrounding organs at risk.Nasopharynx gross tumor volume(GTV-nx) and cervical metastatic lymph nodes gross tumor volume(GTV-nd) were delineated based on the boundaries of the primary tumor and cervical metastatic lymph nodes shown by CT and Magnetic Resonance Imaging(MRI). Clinical target volume 1 (CTV1) is GTV plus 5 ~ 10 mm, including the whole nasopharyngeal mucosa (submucosal 5 mm), clinical target volume 2 (CTV2) nasopharyngeal range is nasopharyngeal cavity, posterior nasal cavity, posterior maxillary sinus, pterygopalatine fossa, partial posterior ethmoid sinus, parapharyngeal space, skull base, partial cervical vertebra or clivus. Lesions exceeding the above structures were defined as GTV plus 10 mm. Neck range is the region of positive lymph nodes and 1–2 neck regions downward. In patients with N0, the lower boundary of CTV2 is at the level of the cricoid cartilage. For patients with positive unilateral lymph nodes, CTV2 included ipsilateral zone II, III, IV, and V lymph nodes, and zone II, III, and Va lymph nodes contralateral.For patients with positive lymph nodes bilateral, CTV2 includes lymph nodes in regions II, III, IV, and V. Whether zone I lymph nodes are irradiated depends on the situation. The same intensity-modulated plan was performed for the upper neck plus lower neck plus supraclavicular region and the primary tumor. Mandatory delineations of vital organs are the spinal cord, brainstem, temporal lobe, pituitary gland, parotid gland, lens, optic nerve and chiasm, temporomandibular joint, and mandible.
The prescribed dose to the target area was 66 to 70 Gy, 2.10 to 2.25 Gy/f for GTV-nx, 66 Gy, 2.00 to 2.25 Gy/f for GTV-nd; 60 to 62 Gy, 1.8 to 2.05 Gy/f for CTV-1; and 50 to 56 Gy, 1.7 to 1.8 Gy/f for CTV-2. The physicist designed the IMRT plan as required, and the treatment was performed using a 9-field split protocol, with all patients treated on a Varian IX treatment machine at a frequency of once a day, five times a week for three times.
Chemotherapy
The weekly regimen was weekly chemotherapy during radiotherapy, and all of them received platinum chemotherapy, with a dose of 25 to 30 mg/m2 per week for cisplatin, a dose of 15 to 20 mg/m2 per week for lobaplatin, and a dose of 30 to 40 mg/m2 per week for nedaplatin.
The three-week regimen was concurrent chemotherapy starting on days 1 to 3 from the start of radiotherapy, 21–28 days per cycle, until the end of radiotherapy.Platinum regimen is cisplatin 25 to 30 mg/m2 or lobaplatin 15 to 20 mg/m2 or nedaplatin 30 to 40 mg/m2 on days 1 to 3.The docetaxel plus cisplatine regimen(DP regimen) was 60 to 75 mg/m2 on day 1 combined with cisplatin 25 to 30 mg/m2 on days 1 to 3.
During chemotherapy, closely monitor the patient's blood routine, liver and kidney function electrolytes, and if the white blood cell count is less than 3000 mm3 or the platelet count is less than 75,000 mm3, delay or discontinue the administration until recovery is observed.
Basic Oral Care And Management
Oral care was routinely performed in all patients during radiotherapy. When oral mucositis occurs, sodium bicarbonate mouthwash, 0.9% normal saline(NS) 100 ml plus lidocaine 5 ml plus dexamethasone 5 mg, and 0.9% NS 100 ml plus recombinant human interleukin-11 3 mg can be used topically to gargle, 3 to 5 times a day, 10 ml/time, containing 5 to 10 minutes before spitting up. Then according to the severity of oral mucositis, 5 ml of lidocaine plus 20 ml of 0.9% NS was given for oxygen nebulization; or topical epidermal growth factor was sprayed to promote mucosal inflammatory surface healing. When oral bacterial culture was positive, antibiotic therapy was implemented on a case-by-case basis, and radiotherapy was suspended if necessary.
Acute Toxicity Assessment
Oral mucositis toxicity was consistently scored three times a week by the physician in charge using the Raditon Therapy Oncology Group/European Organization of Research on Treatment of Cancer RTOG/EORTC scale, and only the highest grade of acute OM in each patient's toxicity assessment was used in the analysis. Oral mucositis is classified as moderate to severe (maximum toxicity score of grade 2 and above) and none/mild (maximum toxicity score of grade 1 or less) because more than grade 2 radiation stomatitis can cause oral pain and has an impact on the patient's quality of life.
Statistical analysis
Statistical analyses were performed using SPSS software (version 26.0). The association between each variable and oral mucositis of grade 2 and above was analyzed by univariate and multivariate logistic regression. In multivariate analysis, stepwise selection was used to enter the regression model for all variables. A p-value < 0.05 was considered statistically significant in all analyses.Categoric variables were tested for association with acute grade 2 and above OM by use of Pearson’stest. Independent-samples T test was used to identify difference between continuous variables from patients with and without acute grade 2 and above OM. Parameters statistically signifificant on thetest and t test analysis were considered for a binary logistic regression analysis to identify determined factors for acutegrade 2 and above OM.In multivariate analysis, stepwise selection was used to enter the regression model for all variables. A p-value < 0.05 was considered statistically significant in all analyses.