Including: 1) General information questionnaire: age, gender, nationality, residence, marital status, education level, working status after illness, medical treatment, chemotherapy plan, times of chemotherapy, days of chemotherapy, disease diagnosis, time of diagnosis, tumor stage, pathological type, metastasis, smoking, drinking, dry mouth, olfactory changes and complications. 2) Chinese version of the chemotherapy-induced taste alteration scale (CiTAS) [5] : prepared by Kano et al. in 2013 to evaluate the degree of taste alteration of chemotherapy patients. In 2017, Qian Lijing et al. authorized by the original author, Sinologized it. The scale includes taste change (6 items), unpleasant taste change (6 items), unpleasant symptoms and problems (6 items), and 18 items in total. The scale uses a Likert5-grade scoring method, from “no” to “very serious” respectively 1 - 5 points, all items are positive scoring. The higher the score is, the more serious the taste change is. The internal consistency coefficient was 0.766 and the retest reliability was 0.705.

The questionnaire was uniformly trained and explained by the researcher himself to the investigator, and was distributed and recycled on the spot. Before all questionnaires were distributed, the purpose of the study was explained to the patient and the caregiver to obtain the understanding and cooperation of the patient and the family members. When the respondents’ physical, visual or educational level affects their answers, they should get the consent of the respondents, and read and explain the questions by the investigator. After the respondents understand and make a choice, they are authorized to fill in the questions on behalf of the investigator. In fact, 240 questionnaires were sent out and 233 effective questionnaires were recovered, the effective rate was 97.08%.

SPSS 19.0 statistical software was used to analyze the data. Frequency and percentage were used to describe the counting data, mean and standard deviation were used to describe the measurement data, and multiple linear regression was used to analyze the main influencing factors of chemotherapy-related taste changes, p < 0.05.

In this study, 233 tumor patients participated in the investigation; 130 patients with dry mouth, 103 patients without dry mouth; 63 cases had olfactory changes and 170 cases had no olfactory changes. See Table 1 for other general information.

Among 233 cases, only 62 tumor patients did not have chemotherapy-related taste changes. Most of the chemotherapy patients had taste changes of different types and severity, as shown in Table 2.

The results of logistic regression analysis showed that the duration of chemotherapy, the days of continuous medication, and dry mouth were the influencing factors for chemotherapy-related taste changes, as shown in Table 3.

The results of this study show that most cancer patients will have different degrees of taste changes at the beginning of chemotherapy, and its severity will gradually increase with the passage of time, until the most serious 3 - 5 days after chemotherapy. Previous studies have reported that chemotherapy-related taste changes may occur in cancer patients during chemotherapy or during the interval of chemotherapy, lasting for several hours or days or months [7] , the most serious 5 - 7 days after general chemotherapy [8] . It can be seen that the results of this study show that the most serious change in chemotherapy-related taste is a little earlier than 1 - 2 days. The analysis of the causes may be related to the strengthening of health education for cancer chemotherapy patients by the specialized nurses of the oncology department, so that they gradually improve their awareness of the change in chemotherapy-related taste. Domestic research shows that chemotherapy related taste changes are usually temporary, and patients can gradually return to normal after chemotherapy, with a recovery time of about 6 months [9] .

Based on the analysis of the results of this study, whether there is dry mouth in tumor patients is the influencing factor of chemotherapy-related taste changes, which is consistent with the conclusion of Qian Lijing and other researchers. The results showed that the type and degree of taste changes were related to dry mouth, olfactory changes and hypertension before chemotherapy. However, it is not clear that the mechanism of xerostomia is related to the decrease of saliva and the limitation of chemical receptors. Rich saliva can provide an ionic environment for taste cells to sense signals and conduct them. Chemotherapy drugs arrive at taste cells in the mouth with blood, producing bad taste, such as salty, bitter or metallic taste [10] . Salivary gland is a very sensitive gland to chemotherapy drugs [11] . Once stimulated by chemotherapy drugs, the gland at the initial stage shows an increase in secretions and oral secretions, which can take away some bad taste. However, the serious damage of chemotherapy drugs to normal salivary gland cells has been irreversible, resulting in the decline of salivary secretion function, and finally, there is a small amount of saliva and viscosity, xerostomia, deterioration of chemotherapy-related taste changes in cancer patients [12] . In addition, relevant domestic research shows that the sensitivity of tumor patients with hypertension and diabetes to sweet and salty tastes is significantly lower than that of healthy people, which may cause tumor patients to take more sugar, salt or condiment, which may aggravate the degree of chemotherapy-related taste change of tumor patients [13] .

The results of this study show that whether or not chemotherapy-related taste changes occur in cancer patients and the severity is not related to gender and age, which is consistent with the results of investigation and analysis by Qian Lijing and other domestic researchers [5] , but through histological research, foreign researchers found that women have more fungiform taste buds and taste pores than men, and confirmed that women’s sensitivity to taste is indeed higher than men’s [14] . McGreevy J and other research report that the change of taste in female patients is often more serious than that in male patients, and with the increase of age, the degree of taste change will decrease [15] . The analysis of the reasons may be related to the gender and age distribution proportion of the study subjects. Early studies have pointed out that the incidence and duration of chemotherapy-related taste changes are different in patients with different tumor types [16] ; when patients with head and neck tumors receive chemotherapy combined with radiotherapy, the incidence of taste changes increases, the occurrence time is earlier, and the duration is longer [17] . This study involves a large number of tumor types, and the sample size of some tumor types may be insufficient. Moreover, the inclusion criteria limit the inclusion of tumor patients undergoing concurrent radiotherapy and chemotherapy, leading to a certain deviation in the results of this study.