The present study was a randomized controlled trial with one intervention and a control group conducted in a double-blind manner.
Sample and setting
The study conducted in one oncology clinic affiliated to the University of Medical Sciences in western Iran from September 2019 to August 2020. Design of study was approved by the ethics committee of the Hamadan university of medical Sciences (Umsha.rec.1398.335), and recorded at the clinical trials Ccentre (IRCT 20160110025929N28). The written informed consent obtained from all the participants after providing them with sufficient information on the study. The sample size for this study calculated based on Chou et al. study with power of 80% and α = 0.05 by using formula . therefore, about 44 patients was estimated for each group, which with the loss of about 10% of the samples during the study, sample size was finally considered 48 people in each group.
Inclusion criteria included: patients with stage 1 or 2 cancer, undergoing chemotherapy, age above 18 years, lack of oral mucositis, being alert and able to use mouthwash unaided, receiving same chemotherapy (fluorouracil, mitoxantrone), lack of leukemia, lack of pregnancy, lack of breast feeding, lack of history of smoking, lack of immune deficiency, lack of oral cavity disease prior to the start of chemotherapy, lack of underlying diseases (diabetes as well as liver, renal and digestive diseases) and willingness to participate in the study. Exclusion criteria were thrombocytopenia, worsening of the patient's condition, increase in the degree of oral mucositis and treatment discontinue for any reason.
Recruitment and allocation
After determining the sample size, a total of 106 patients were screened for eligibility; 10 patients were ineligible and finally, 96 patients who gave written informed consent were enrolled and randomly assigned to one of two groups (zinc chloride mouthwash, 48 subjects and control, placebomouthwas,48 subjects) using block randomization. Sequentially numbered, opaque, sealed bottles with similar shape, color and size containing of zinc chloride mouthwash and placebo were used to conceal the allocation sequence and to maintain blinding and necessary measures were taken so that the sequence would remain concealed until the intervention was allocated to the intervention groups. The allocation sequence and packages were prepared by a pharmacologist, a faculty member of Hamadan university of medical Sciences, did not involve in the recruitment, data collection and analysis.
The protocol of this study was designed based on the opinion of a pharmacologist and trusting the protocol of two studies Cabrera et al. and Rambod et al. [5, 15]. Therefore, mouthwashes for all patients of zinc chloride and placebo in this study were prepared by a pharmacist specializing in pharmaceutics in the clean room of Hamadan university of medical sciences. Mouthwash for the zinc chloride group containing zinc chloride 0.2%, greasy mint, preservative and mouthwash for the control group were similar to the intervention group but lacked effective material. All patients in two groups were educated in routine oral care (teeth brushing, proper nutrition, and mouth hygiene). The patients in each group should rinse their mouths every 8 h two times and each time 2 min with 7.5 ml from mouthwash. The time interval between each mouthwash was 15 min. Participants in the two groups rinsed their mouth so that the mouthwash covered the tongue, palate, throat, inside the cheeks, and all the tissues of the mouth well.
These included age, sex, marital status, employment and finances, type of cancer, duration of cancer, frequency of chemotherapy, number of decayed teeth, and history of oral and gingival disease.
The severity of oral mucositis was measured by using the world health organization criteria for grading of oral mucositis. This scale measures objective (redness, edema, and wound development) and subjective symptoms (dysphagia and mucosal severity). Accordingly, mucositis is classified to five levels (0–4). Asymptomatic (0); ulcers, redness in the mucous membranes of the mouth, gums, tongue, and palate is low (1); there are redness, inflammation, and multiple ulcers in the patient’s mouth, but they can eat solid food without pain (2); significant redness, inflammation and ulcers in the mouth and the ability to eat soft foods and liquids (3). Redness, inflammation and several ulcers in the mouth with pain and difficulty swallowing that make it impossible to eat food (4). This scale has content and face validity and internal reliability of 0.91 in Iranian society [18, 19]. The clinical nurse in oncology clinic with ten years of experience(assistant researcher) who was not aware of the allocation of individuals in intervention and control groups observed patients' mouths and completed the world health organization criteria in the baseline, first, second and third weeks for each patient and recorded mucositis grade.
Weight of the patients
Weight of the patients assessed at two time points: baseline and 3 week after the intervention at a specific time (7 am). Patients wore the same clothes each time that weight was measured using a digital scale (Beurer®, Germany). This digital scale was calibrated each week by a medical engineer. The clinical nurse in oncology clinic with ten years of experience(assistant researcher) who was not aware of the allocation of individuals in intervention and control groups observed and reported patients' weight the at the beginning and end of the study (third week).
Data analyses were conducted using SPSS version 22. To analyze the data, descriptive statistics (namely frequency, percentage, mean, standard deviation) was used and inferential statistics including chi square and fisher’s exact test (comparison of data distribution), covariance (adjustment of confounding variables), Mann Whitney U test (comparison oral mucositis between groups in non-normal distribution), Friedman’s nonparametric test (comparison oral mucositis intra-group comparison). The independent t test (comparison of weight of the patients between groups) and dependent t test comparison of weight of the patients (intragroup comparison). P values of less than 0.05 were considered statistically significant for all tests expect of Mann Whitney U test that p values of less than 0.00025 were considered statistically significant.