Breast cancer is the most common cancer in women worldwide. According to the 2018 global cancer statistics report, the global incidence of breast cancer is 2.1 millions, accounting for 24.2% of female cancer incidence and 15.0% of the total number of deaths [1, 2]. The number of new cases of female breast cancer in China is 279,000, accounting for 16.5% of female cancers and ranking the first in female cancers . The treatment methods of breast cancer mainly include surgery, radiotherapy, chemotherapy, targeted therapy and endocrine therapy. One or more combination of diagnosis and treatment schemes have inevitable side effects, and the treatment cycle is longer, which brings a series of damages to health and greatly affects the quality of life [4, 5]. Although the life cycle of breast cancer is continuously extended with the continuous improvement of medical level, breast cancer patients still suffer from severe physical and mental pain caused by the disease in the treatment and rehabilitation period. With that passage of time of treatment, the patient still need to continuously bear the huge social, psychological and spiritual burden caused by the damage of body image, changing role, influencing sexual life and worry about cancer recurrence [6, 7]. Therefore, patients with breast cancer are eager to find spiritual sustenance, gain hope, love, forgiveness and strength, understand the significance and value of life and overcome the pain and dilemma, i.e., spiritual care needs . In addition, there is ample evidence that spirituality plays a vital role in the treatment of breast cancer patients and in the promotion of overall health by providing them with inner strength, peace and comfort as a way to cope with cancer during their diagnosis, treatment and rehabilitation [9–11].
Spirituality, originated from the Latin "spiritus", which means breathing, representing an indispensable part of life . The National Consensus Project for Quality Palliative Care (NCP) clinical practice guidelines for high-quality hospice care pointed out that spirituality is a way for people to find and express the meaning and purpose of life, and also a way to experience the connection between self and the present, others, god, the natural environment and beliefs . Spiritual care meets the spiritual needs of patients through listening, accompanying or discussing the meaning and value of life with patients according to the assessment results of individual spiritual needs/troubles, including helping patients to find the meaning and purpose of life, giving love and forgiveness, and obtaining internal and external resources. It enables patients to obtain peace and comfort and provides individual care measures or activities consistent with their culture and beliefs [14–16]. At present, the definition of spiritual care needs has not been unified, and the most common definition currently used is that it refers to the expectation and need of everyone to find the meaning, value and purpose of life, as well as the need to understand their connection with the present, self, others, god/holiness, faith and nature [17, 18].
The Practice Guide for Hospice Care (for Trial Implementation) (2017) in China points out that hospice care should include providing spiritual care for patients . It has been proposed in many studies that spirituality is the cornerstone of holistic nursing practice, and that the assessment of patients' spiritual care needs is the first step in developing targeted intervention programs for them [20–22]. Many studies abroad have shown that spiritual care for patients with advanced cancer and meeting their spiritual care needs are conducive to alleviating pain, relieving discomfort, promoting recovery and prolonging life expectancy [14, 23–25]. Research by Weathers et al.  has shown that providing supportive spiritual care with connectivity, transcendence and life significance and addressing spiritual care needs is important component of implementing high-quality spiritual care for patients. The results of a qualitative research conducted by Wang et al.  showed that spiritual care based on spiritual needs and distress can promote patients with advanced cancer to establish good interpersonal relationships, obtain emotional support and relieve inner fears and contradictions. In addition, Michael et al.  found that improve the needs of spiritual dimension can increase the quality and satisfaction of holistic care. However, for breast cancer patients who have suffered from the special physical and mental effects of cancer for a long time, their need for spiritual care may be more intense .
As the incidence of breast cancer increases and continuously prolongation of survival time, relevant studies on the spiritual care needs of breast cancer patients overseas are increasing. A qualitative study by Devi et al.  found that transcending experience, meaning and purpose, and changing views are common expressions of spiritual care needs of newly diagnosed breast cancer patients in Singapore. Research by Lynn et al.  showed that breast cancer patients believe that through spirituality and religion (including attending religious ceremonies, prayers, worship and reading the Bible, etc.), they can get comfort, encouragement and strength to help them cope with the pain during diagnosis and treatment. A qualitative study by Phenwan et al.  found that the sense of life value, collective belonging and natural connection were the connotations of patients' spiritual happiness. Park et al. demonstrated that spirituality of breast cancer survivors can promote the formation of healthy behaviors of patients through a variety of ways, thus positively affecting the health outcomes of patients. Fallah et al.  found that the integration of spiritual care into group psychological intervention could significantly improve the happiness, hope level and life satisfaction of breast cancer patients. Jafar et al.  performed spiritual intervention for breast cancer patients based on the Iranian cultural background, and the results showed that the mental well-being of the patients was effectively improved, and the quality of life was significantly improved.
At the same time, many studies in China have also revealed that there is a widespread spiritual care needs for breast cancer patients [35–37]. However, due to the differences in religious beliefs, traditional cultures, and values between the East and the West, the unique spiritual care model suitable for China's national conditions is still under continuous exploration. Many reasons together limit the improvement of nurses' spiritual care perspectives and competence, resulting in the mismatch with patients' spiritual care needs, and the ineffective satisfaction of their spiritual care needs . Additionally, in terms of research methods, the qualitative research was mainly adopted in the domestic research on the spiritual care needs of breast cancer patients. Besides, the existing research contents in China and abroad mainly focused on the analysis of the status quo of the spiritual care needs scores, and few studies have qualitatively explored the attributes of spiritual care needs of breast cancer patients by using analytical models, such as the Kano model. Kano model is a simple method to identify service need attributes, which is mainly used in service industry at first. It can identify the quality attributes of customer' s service need accurately. In recent years, some scholars in China and abroad have applied Kano model to the field of health care to determine patients' needs for medical and nursing services, which is of great significance to improve patients' satisfaction [39, 40]. The model is easy to operate, and can identify various quality attributes and conduct regular and qualitative analysis on attributes. Moreover, the empirical research results of Kano model in multiple fields showed that the classification of need attributes is of great significance for the satisfaction of needs [41, 42].