In this retrospective study, relevant data were collected to evaluate the incidence and risk factors of radiodermatitis after radiotherapy after breast conserving surgery in female breast cancer patients. Reasonable study design was adopted to collect and evaluate patients’ symptoms every week during and after radiotherapy, so as to ensure timely and accurate data collection and objectivity. However, the main defect of this study is that the data comes from a single medical center, which may affect the results of the factor analysis and lead to biased results.
Among the factors that affect radiodermatitis, clinical radiologists paying more attention on radiation factors than genetic factors, as the genetic factors are harder to intervene than the radiation factors. In nursing aspect, by contrast, the part that allows for early intervention is the individual factors. At present, the empirical data of individual factors are very limited, but they are the most concerned and interested part of clinical radiology nurses. In the risk factors which related to radiodermatitis, the study controlled for radiotherapy factor related variables, by focusing on individual variables such as individual factors and genetic factors related to the partial treatment, and combining relevant literature, to expend corresponding nursing measures.
Under normal circumstance, the skin is in a continuous process of metabolism, the surface cells shed, the basal cells divide and multiply, migrate toward epidermis, keratinization. However, radiotherapy can lead to irreversible double-strand breaks in DNA of basal keratinocytes, stem cells in the hair follicles and increased melanocytes production. The migration of immune cells such as leukocytes to from circulation toward to irradiated skin area is the significant hallmark of radiodermatitis. Thereafter, the death of epidermal cells, biochemical changes in endothelia cells and DNA destruction, as well as inflammatory reactions that can cause skin damage .
In the existing studies on risk factors of radiodermatitis, empirical evidence shows that age, skin characteristics, nutritional status, basic diseases, race, smoking, genetic factors, radiation dose, concurrent chemotherapy and irradiation site are closely related to radiodermatitis . In this study, according to logistic regression analysis that age below 35 years, fair skin, treatment time in summer, BMI above 25, local thermotherapy, sun exposure, hot water bath, skin scratch and bra wearing were risk factors for radiodermatitis in patients. The protected factors of the affected limb were akimbo in day time and elevation of the affected limb before bedtime (P<0.05, P<0.01).
Body weight/ BMI/ smoking/ diabetes
Body weight, BMI, smoking, diabetes which are metabolic diseases are different from some foreign studies in multivariate analysis of patient own factors, which did not exclude the limitations caused by monocentric study and ethnic differences. According to Beamer (2019) , body weight and BMI can be seen as an evaluative parameter to predict the degree of radiodermatitis, as the data has shown that more dermatitis responses in heavier patients than in lighter patients, whilst age and height had no effect on radiodermatitis. In this study, we obey the BMI standard which seen BMI>25 as overweight and BMI>30 as obese, while the results have been showed that in the radiodermatitis group in table 1, there are 55 out of 57 of patients whose BMI ≥25; This means BMI significantly can be a risk factor of developing radiodermatitis.
Furthermore, Marinello et al. (2016)  noted that smoking history has been included as a risk factor for radiodermatitis, as smoking aggravates the microcirculation abnormality that caused by radiotherapy. Due to the low proportion of smoking history in the enrolled patients in this study, they were not included in the study scope. Further relevant studies are needed to determine whether metabolic abnormalities such as obesity and diabetes that affect the repair mechanism of radiological damage to the skin.
Adjuvant radiotherapy after breast conserving radical surgery can reduce the local recurrence rate of breast cancer, among which patients with high risk factors that need adjuvant chemotherapy to improve their survival rate. Although radiotherapy combined with adjuvant chemotherapy can exacerbate adverse reactions, but generally for most patients with good tolerability, postoperative radiotherapy and adjuvant chemotherapy are safe and feasible. Radiotherapy combined with adjuvant chemotherapy also demonstrated improved rates of breast conservation and reduced risk of locoregional recurrence, which are safe and feasible . In this study, the factor of concurrent chemotherapy was taken into consideration to analyze whether it aggravates the incidence of radiodermatitis.
Patient age ≤ 40 years
Age ≤ 40 years for the viewpoint that the prognosis of young women with breast cancer is worse than that of elderly women, relevant western studies define the range of young women as ≤ 40 years, while the Chinese domestic literatures classified the age as ≤ 40 years as well [17–18]. In terms of this study, age ≤ 40 years was considered as one of the risk factors for the occurrence of radiodermatitis, and statistical analysis was conducted.
Skin color and sun exposure
The grating characteristics of Chinese women’s skin color were evaluated in this study. The effect of X-ray radiation on the skin during radiotherapy depends on how sensitive the skin towards to the radiation . Considering that the principle of the action of rays on the skin is similar to the reaction of the skin caused by solar irradiation, this study suggests that the sunlight reaction can be related to dermatitis reaction of patients. In this study, the skin color of patients was evaluated and the degree of sunlight exposure of patients to their skin color and daily activities were also evaluated. From level 1 (always exposure to the sun, rarely tanned) to level 4 (rarely exposure to the sun, but easily tanned), in order to reflect the sensitivity of the patients to radiation, and thus to infer the possibility of radiodermatitis. According to the study of Yamazaki et al. (2011) , skin pigmentation of patients after radiotherapy was predicted by skin color changes that caused by sun exposure; This study believed that the degree of sun exposure and skin color of patients could be used as criteria to judge whether patients were at high risk of radiodermatitis.
When the treatment time is summer, the climate is hot and humid, the capillary diastole and the blood circulation is rich. Increased sensitivity of vascular endothelia cell to the radiation, coupled with more local skin sweating, thus increase the chance of wet dermatitis. There are few research data and references in this filed. Combined with the experience of a large number of clinical nurses, it is considered that the admission time of patients with radiodermatitis is concentrated in summer. Therefore, the correlation between seasonal factors and the incidence of radiodermatitis was statistically analyzed.
Local thermal therapy
Local thermal therapy is an advanced and effective method to treat tumor. The clinical trial has shown that the combination of thermal therapy and radiotherapy can significantly improve the local control rate of tumors and the survival rate of patients . Lilla et al. (2007)  reported that the radiotherapy circumstance of 416 cases of breast cancer patients after breast conserving surgery, and analyzed the significant relationship between radioactive dermatitis and telangiectasia, this allowed for local hyperthermia to cause telangiectasia at the site of radiotherapy. At the same time, combined with relevant studies and analysis, it was found that although adverse reactions to thermal therapy were relatively mild, it can still cause blisters, subcutaneous indentation, subcutaneous pain, and even more serious skin damage such as radiodermatitis . Therefore, local thermal therapy was included in this study.
A hot bath/ scratching the skin/ Wearing a bra/ exposure to the sun
After the patients with a diagnosis of breast cancer have had radiotherapy, the skin tissue where has been accepted radiation became thinner than before, particularly prone to skin reactions. Relevant evidence-based nursing studies show that in order to reduce reaction after radiotherapy, relevant skin care measures include: 1) Educating patients to wear cotton underwear to avoid skin friction in and around the radiotherapy area. 2) Local soap scrubbing or hot water bath and sun exposure are prohibited to avoid skin irritation in the radiotherapy area. 3) When the skin in the radiotherapy area is itchy and unbearable, gently pat the local skin with their hand, cannot scratch the skin . Although such nursing education is conducted by nurses to patients in daily clinical care, the effects of activities such as hot baths, scratching of skin, wearing of bras and exposure to the sun on radiodermatitis are still discussed and analyzed in consideration of the differences in patient compliance.