Patients with cancer can experience various complications both during and after treatment. Among these complications, problems related to sexual health have been found to have a particularly negative impact on patients' quality of life [1].

Treatment methods, such as chemotherapy and radiation therapy, may lead to decreased sexual desire, menopausal symptoms, vaginal dryness and atrophy, pain during sexual intercourse, and fertility dysfunctions [12]. A radiation dose greater than 20 gray can cause male infertility by decreasing sperm production, resulting in permanent azoospermia [1], and it may cause females to experience ovulatory dysfunction and early menopause [3]. In patients with reproductive cancers, such as prostate, testicular, and gynecologic cancers, sex-related problems are particularly severe after sexual organ resection [4]. In addition, depression, fatigue, and changes in body image caused by hair loss and skin and weight changes threaten the sexual health of patients with cancer [5]. Cancer treatment typically causes long-term fertility complications [26], with 30~75% of male patients and 40~80% of female patients becoming infertile because of chemotherapy and radiotherapy [7]. Hence, cancer treatment negatively affects patients' abilities to complete normal developmental tasks at individual and societal levels, as well as their quality of life [1].

Fertility preservation involves safeguarding patients' reproductive capabilities before performing medical treatment that can cause fertility loss [8]. A great deal of research has focused on preservation approaches such as cryopreservation of sperm, egg, embryo, ovarian tissue, and testicular tissue; ovary transposition; and the use of gonadotropin-releasing hormone releasing agonist [89]. Reproductive-aged patients with cancer, especially younger patients, desire information on fertility preservation [10]. Hershberger et al.[11] revealed that the provision of information on fertility preservation and medical staff's attitudes are determined by patient preferences, personal values, and the medical staff's in-depth understanding of individual patients' situations. However, medical staff often feel uncomfortable discussing fertility preservation with patients with cancer, and may even avoid the discussion altogether because they lack sufficient knowledge, have little time to discuss relevant issues, and tend to assign priority to treatment aimed at improving survival rates [12]. Studies have shown that 34~72% of young patients with breast cancer discuss fertility-related issues with their physicians [13], and many female patients feel their concerns are not appropriately addressed in discussions with their physicians [13].

Although the need for specialized sexual health education for patients with cancer has been continuously suggested, most existing programs focus on the physical symptoms of sexual problems and sexual function management, while fertility preservation has largely been excluded [14]. Logan and Anazodo [15] conducted a global systematic analysis of 33 fertility preservation guidelines and reported that 29 of them provided clinical recommendations on fertility counseling, indicating that fertility counseling is an important part of counseling for all cancer patients. Oncology nurses need to educate patients' families about infertility risks and other fertility-preserving issues [16], and can actively get involved in patients' decision-making process regarding their treatment choices [17].

Fertility preservation counseling and education programs need to sensitively address individual patients' situations; thus, nurses should enhance their understanding of potential fertility-related problems, fertility preservation options, and how to help patients make proper decisions by providing systematic information. Therefore, nurses' current level of knowledge regarding fertility preservation should be examined. Accordingly, this study aimed to investigate nurses' level of knowledge of fertility preservation for patients with cancer, and to create a measurement scale that can be used to develop educational materials and guidelines.

This study was conducted to assess the current awareness of fertility preservation among nurses who care for patients with cancer. This was done with the aim of providing the basic data necessary for establishing the relevant guidelines, and to help in preparing nursing interventional programs regarding fertility preservation decision-making.

The mean of oncology nurses' fertility preservation knowledge level was above average, as were the scores on the three subdomains. Armuand et al. [24] observed that neither did most young patients with cancer receive adequate information about fertility preservation nor were they referred to experts in the field, partly because the oncology professionals themselves did not have enough knowledge regarding fertility preservation methods [12]. We measured nurses' knowledge of fertility preservation using an instrument developed specifically for this study; therefore, direct comparisons with previous studies cannot be made. However, future studies must assess whether a moderate level of knowledge of fertility preservation is adequate for nurses to provide sufficient information to patients.

Patients with cancer can now live longer than was previously possible, owing to improved treatment methods. The increased number of young cancer survivors indicates that quality of life-related topics, including pregnancy following treatment, have emerged as factors to be seriously considered in relation to cancer treatment [25]. Researchers have stressed that medical staff need to inform young patients with cancer about the possibility of post-treatment infertility and offer them an opportunity to choose their preferred method of fertility preservation [26]. Fertility loss causes both psychological distress and decreased quality of life in patients with cancer [27]. Therefore, nurses should make an effort to improve their knowledge of fertility preservation by accepting opportunities to receive relevant information and education.

In this study, the level of knowledge regarding fertility preservation was higher among married nurses. This result is in line with a prior study [28], which reported that fertility preservation choices such as embryo cryopreservation were more common in married or partnered women, showing that fertility preservation choices are affected by marital status It is commonly expected in South Korean culture that once an adult, an individual will get married and become a parent, and this sociocultural point of view also applies to most young patients with cancer. This viewpoint becomes more concrete after marriage, and nurses who are themselves in this stage of life can be empathetic regarding patients' fertility-related problems, such that they explore relevant information to offer help, thereby improving their own knowledge regarding fertility preservation. In a society where it is considered a rite of passage for an adult to become a parent, failure to do so means loss of the most important role in life, as perceived by society [29]. This can lead to either damaged self-affect or the experience of ego crisis among young adults. Eventually, one's entire life can become defined by the infertility status, and patients may consider this their greatest life crisis. Therefore, oncology nurses need to focus on fertility preservation for patients with cancer and establish diverse supportive strategies that account for biological and sociocultural perspectives.

In addition, knowledge of fertility preservation was higher in nurses with more total nursing experience. These results were consistent with a previous study [30]. This seems to be a result of the patient-nurse interactions that occur during the care experience. Throughout the treatment process, from diagnosis to follow-up, nurses share a variety of experiences with patients, including the difficulties associated with the cancer diagnosis and treatment side effects, and the anguish over how to deal with these difficulties. These experiences accumulate as the length of a nurse's career increases, resulting in high nursingrelated knowledge in general and knowledge regarding fertility preservation in particular. Nurses who care for patients with cancer in clinical settings should perform a patient-customized intervention that accommodates the diverse consequences of the cancer type and treatment on fertility. The fears that are commonly felt by patients with cancer should be shared, and it is essential to recognize the need to provide them with adequate information and emotional mitigation and support.

The results of this study show that knowledge regarding fertility preservation was greater among nurses who believed the first patient assessment was the appropriate time to discuss fertility preservation than it was in nurses who responded that there was no particular need to assign a separate time for such a discussion. This finding suggests that even though future fertility is an important item for discussion during the counseling session conducted at the time of cancer diagnosis [26], not all nurses who care for patients with cancer in clinical settings actively make assessments regarding fertility preservation or clearly understand the appropriate timing for such assessments.

Assessing topics related to fertility preservation may negatively affect patients with cancer. If treatment is delayed because of fertility preservation, the cancer may progress or metastasize. The effectiveness of some methods of fertility preservation has not yet been established; therefore, research is in progress, and the overall pregnancy success rate is low [1]. In addition, surgery may be required to extract tissue to freeze, and the hormone used to induce ovarian hyperstimulation to extract eggs can affect the tumor in hormone-sensitive cancers [1]. Nevertheless, patients with cancer can strongly desire fertility preservation and request information to help them choose from among the available options [31]. Accordingly, healthcare professionals need to make careful observations about the benefits and losses patients may experience as fertility preservation technology advances [32]. Medical staff should provide patients with information regarding choices and methods of fertility preservation before performing medical treatment that affects fertility [19], and provide counseling to make a multidimensional assessment that includes the patient's present and future sexual health and enables the striking of a balance between fertility preservation and cancer treatment.

Many nurses simply answered patients' questions or partially explained fertility preservation, rather than initiating an in-depth assessment. Additionally, the level of knowledge regarding fertility preservation was higher among nurses who were active in providing nursing care, especially by using written data such as handbooks or brochures, compared to nurses who never provided such care. These findings demonstrated that nurses' attitudes toward sexual health contribute to the nursing care they provide in relation to sexual health. Fertility-related issues are important elements in assessments of patients' sexual health; however, it can be difficult for both parties to approach these issues. According to a previous study conducted in South Korea, both nurses and patients typically have passive attitudes toward sexual health problems [33]; therefore, the nursing approach to sexual health problems is, in itself, problematic. As sexual health problems are unfamiliar topics of discussion between healthcare professionals and patients, such that they are often not spoken about in detail unless the patient directly asks about them [34], it can be quite difficult to provide sexual healthcare in clinical settings. Moreover, health care providers tend to focus only on the outcome of cancer treatment, rather than on sexual health problems, because they themselves are not confident in their knowledge of sex-related changes after cancer treatment [35]. Therefore, it is difficult for them to set aside the time to provide sexual counseling to patients, and this leads to inadequate sexual health interventions. One recent study [11] showed that useful strategies to help patients with decision-making with regard to fertility preservation involved providing situationally appropriate information to individual patients using a handbook or website and encouraging positive attitudes among medical staff. Therefore, nurses should have an in-depth understanding of the sexual health-related side effects that can occur during cancer diagnosis and treatment, including issues concerning fertility impairment and preservation, to ensure they can actively assess patients' needs and provide the necessary interventions.

Nurses' knowledge level regarding fertility preservation did not significantly differ based on beliefs concerning who the most appropriate person to discuss the subject matter with patients is; however, 80% responded that it should be a physician. This indicates that it is desirable to discuss fertility preservation before treatment begins, when a plan for the entire treatment process is made and the scope of treatment determined. Healthcare providers should take medical conditions, treatment plans, and ideal outcomes into account when treating patients with cancer and be aware of a treatment's estimated side effects, including possible effects on future fertility [32]. In addition, nurses, who interact more with patients than do any other oncology team members, should assume the role of counselor with regard to fertility preservation. Nurses who care for patients with cancer should be aware of the fertility-related complications experienced by patients with cancer, and make an effort to perceive and aim to solve individual patients' problems. Furthermore, education that is based on a comprehensive understanding of overall sexual health should be provided to increase nurses' sensitivity to sexual health-related problems, particularly the fertility-related problems of young patients with cancer. Finally, educational materials for patient counseling and education should be developed, and culturally and situationally appropriate guidelines should be established in South Korea.

As this study assessed the fertility preservation-related knowledge of oncology nurses from a single hospital, it is not appropriate to generalize the results. This study did not assess general knowledge related to oncology nursing, which could affect nurses' knowledge of fertility preservation. In addition, the validity of the measurement tool was not precisely examined. Despite such limitations, considering the absence of clear guidelines for fertility counseling and education for cancer patients, the contribution of this study is in helping identify the necessity of all oncology nurses informing and educating patients about fertility preservation throughout the decision-making process, from the diagnosis of cancer to the preparation of treatments.

The increase in the number of young patients with cancer and improved survival rates indicate that fertility preservation has become an important factor affecting the quality of life of patients with cancer. Nevertheless, many nurses who work closely with these patients do not have much knowledge of fertility preservation. Therefore, nurses who handle patient problems, including overall lifetime fertility, should develop a deeper understanding of the possible harmful effects of different cancer treatments on fertility. It is also necessary to identify individual patient needs through continuous assessment and, when necessary, refer patients to appropriate specialists from before the beginning of treatment until its conclusion. Furthermore, nurses should be provided with training to improve their communication skills, especially concerning the subject of fertility preservation, and relevant educational materials and guidelines should be developed.