It is generally accepted that malignant neoplasms (MNs) are one of the most common causes of morbidity and mortality. There is a trend toward an increase in cancer incidence rates worldwide; based on data from the International Agency for Research on Cancer, more than 12 million new cases of cancer and about 6.2 million deaths from it are registered every year. The annual growth rate of MNs is approximately 2%, which exceeds the world population growth by 0.3–0.5%. By 2050, experts predict an increase in cancer incidence to 24 million cases worldwide and mortality to 16 million annually registered cases [1].

The highest mortality rates among men were observed in Eastern Europe – 171.0 per 100 thousand, the lowest in Central America – 67.4 per 100 thousand. High mortality among women was noted in Melanesia – 120.7 per 100 thousand, and the lowest also in Central America – 64.2 per 100 thousand [2].

As for the epidemiological situation in Russia, in 2022, 624,835 MN cases were detected for the first time in life (283,179 and 341,656 in male and female patients, respectively). Compared to 2021, this indicator increased by 7.6% [3]. The annual mortality rate from cancer in Russia is more than 278 thousand patients (278,992 in 2021). Over the past 20 years (from 2000 to 2021), the absolute number of deaths and the value of the indicator decreased by more than 5%. Mortality among the male population has decreased even more (-29.22%). The standardized mortality rate from MNs for the male population was two times higher than for the female population. The overall decrease in mortality is explained by anti-cancer preventive measures carried out by oncologists and by modern methods of diagnosis and treatment [4].

The situation is less dramatic among children and adolescents. In 2019, 3759 MN cases were registered in Russia among the child population (0–17 years old), including 3182 cases among children (0–14 years old) and 577 cases among adolescents (15–17 years old). In the same year, only 842 children (0–17 years old) died in the country, among the child population (0–14 years old) – 715, and among adolescents (15–17 years old) – 127. In 2020, 3173 children (0–14 years old) were recorded, that is, 586 less than in the previous year (-15.5%) [5].

The medical and social component of the public health problem of MNs is due to mortality from suicide. Researchers emphasize that suicide mortality in oncopathology is not the main cause, but the standardized mortality rate from suicide in cancer patients is 1.5–1.7 times higher than in the general population [6][7]. This is confirmed by retrospective population studies covering a total of millions of people with a follow-up of several decades and including various socio-demographic indicators (race, gender, age, diagnosis, and mortality ratio from cancer suicides). It was established that the risk of suicide in patients with MNs, regardless of gender, was two to four times higher than in the entire population of 10 European countries, Australia, Japan, and the USA [8]. Moreover, MNs are usually associated among the population with the fear of death, disability, pain, and helplessness, giving rise to serious psychological problems. In the dynamics of the disease, this can lead to increased mental stress, long-term and severe mental disorders, personality changes, and actualization of suicidal behavior [9]. In general, suicides among patients with MNs account for 15–18% of the total number of suicidal autoaggression cases among the population. In the dynamics of oncological disorder in the progressive and terminal phase of MNs, the intentional desire to die or hasten death is 17% [10].

Undoubtedly, theoretical analysis of the problem of suicidal behavior in patients with oncological diseases is relevant, as it allows identifying factors forming suicidal behavior, and also identifying clinical features, methods, and specificity of suicidal behavior in relation to the MN form. In addition, the information obtained can be used to develop preventive programs for suicidal behavior in such patients.

The study aims to analyze modern data on the problem of suicidal behavior in oncological patients.

This literature review was conducted in accordance with the aim of the study (search for high-quality systematic reviews on the prevalence of suicidal behavior in cancer in a comparative aspect, i.e. with general population suicide rates). To more thoroughly and correctly select the material, the author followed the recommendations for compiling reviews and meta-analyses but emphasized the consistency of the methodology for conducting literature reviews to ensure an accurate presentation of the results. The recommendations include key points such as objectivity, completeness of other authors’ results presented, a clearly formulated issue, description of all information sources (e.g. databases with dates of coverage), of the study selection, and of the characteristics for data extraction (e.g. study size, follow-up period), citation or references, the overall interpretation of the results in the context of other evidence, descriptions of funding and other support (e.g. provision of data), and the role of sponsors of the systematic review [11].

In total, 49 sources of Russian and foreign authors were analyzed, excluding duplicate materials (14 sources) during data processing after reading the title and abstract of each article. The search was carried out across specialized medical resources, namely: RusMed, Medline, PubMed, and Web of Science. In addition, electronic libraries were used, such as eLIBRARY.RU, CyberLeninka, and the Library of Dissertations and Abstracts of Russia (dslib.net).

During the preparatory study of the literature, the keyword “suicide” appeared as a term commonly used to denote the problem under study; this subsequently allowed adopting the search formula “suicide and somatic diseases” and “suicide and oncological diseases”. The search in the databases was not limited by the date of publication, although the emphasis was on publications over the past 10 years (2014-present).

The material was selected according to the following criteria:

Descriptive analysis was used to summarize the data obtained.

Despite the fact that cancer patients (oncopathology is the only chronic somatic disease associated with an increased risk of suicide in men and women) belong to one of the most suicidal categories, the statistics and phenomenology of suicide in this group remain poorly studied. This probably explains the wide range of epidemiological data. Thus, the mortality rate due to suicide in Western Europe and the USA fluctuates within 0.2–0.32% [7][12][13], while suicidal thoughts in cancer patients, regardless of gender and without psychiatric pathology, were recorded from 0.8 to 71.4% compared to the registered prevalence of suicidal thoughts in the general population, which ranges from 1.1 to 19.8% [8]. The suicide rate in patients with MNs is statistically 100–1100% higher than in a comparable population group [13].

Suicidal activity is detected in various localizations or types of oncological disorders. The highest risk is associated with cancer of the lungs and bronchi, oral cavity and pharynx, esophagus, stomach and pancreas, head and neck, and Kaposi's sarcoma in HIV-positive patients [13]. For example, a three-year period (1992–2009) of observation of 46,309 patients and 107,736 study participants not suffering from cancer showed that there were 146 suicide attempts and 63 completed suicides. The risk of completed suicide was 3.5 times higher among patients with myeloma and 1.9 times higher among patients with lymphoma but did not increase significantly among patients with leukemia, regardless of the gender of the subjects. A history of precancerous mental disorders increased the risk of suicide by 15–30 times, but high suicide risks were also observed among patients without such history [14]. A retrospective population-based study was also conducted using nationally representative data from the Surveillance, Epidemiology, and End Results program for 1973–2014. Among 8,651,569 cancer patients, 13,311 committed suicide; the suicide rate was 28.58 per 100,000 person-years. The highest standardized mortality ratios were in patients diagnosed with lung, head and neck, testicular, bladder cancer, and Hodgkin's lymphoma. In patients under 50, most suicides were associated with hematological and testicular tumors, and in people over 50 with prostate, lung, and colorectal cancer [15]. Numerous studies revealed that men aged 65 and older with lung, pancreatic, head and neck, or prostate cancer were at particularly high risk of suicide [16]. Foreign studies illustrate the association of suicidal behavior with the cancer type. A total of 9,300,812 cancer patients (48.8% women) aged 0 to 80+ (6,417,560, or 69.0% of them were over 60 years old) were examined between 1975 and 2016. Suicide was detected in 14,423 patients, which is 0.26% of all deaths. The highest mortality rates were found in patients with respiratory system cancer, followed by patients diagnosed with oral cavity and pharynx cancer, myeloma, bone and joint cancer, digestive system cancer, brain cancer, and other types of nervous system cancer. However, the highest risk of suicide was observed in patients with laryngeal cancer in the first two months after diagnosis; during this period, the risk in these patients was 15.8 times higher than in the general population (corresponding to 33.54 additional deaths per 10,000 person-years at risk) [17]. It seems that the localization of cancer does have important clinical significance for predicting the possibility of developing suicide risk.

Differences are revealed in the choice of the suicide method. Among non-oncological patients, in 70–80% of cases, drugs are used for suicidal purposes, supplemented by acetic acid, organophosphorus compounds, and other chemicals. In cancer patients, the proportion of self-poisoning with medications increases over the course of the disease, reaching, especially among women, almost 100% [12][18].

Modern studies illustrate patients' preference for self-poisoning (64.5%), women predominating (85.5%). Frequent use of prescribed psychotropic and analgesic drugs, including narcotics, as a means of suicide is reported; these are all classes of analgesics (Baralgan, Pentalgin, Tramadol, etc.), psychotropic drugs (usually Phenazepam and Amitriptyline), as well as drugs that are prescribed to correct a particular syndrome caused by the tumor (antispasmodics, antihypertensive drugs, etc.). The use of several classes of drugs at once leads to more rapid and severe poisoning, which significantly reduces the possibilities of detoxification therapy [12]. Some authors rightly believe that introducing reliable and accessible psychosocial oncology programs to support the mental health of this category of patients is justified [19]. It is recommended to regularly assess suicide risk factors during the treatment of oncological diseases [20].

Notably, suicide in patients with MNs is rarely a spontaneous act, since a possible suicide attempt is planned over a fairly long period of time. Before committing suicidal acts, about 80% of patients visited an oncologist, and they indirectly or openly reported their suicidal intentions to family members. In addition, doctors, as a rule, are aware of the depressive state of their patients but tend to downplay the degree of distress in cancer patients [10]. It is necessary to introduce methods for the active detection of suicidal tendencies in oncological patients by both senior specialists and nurses.

An increased risk of suicide is associated with brain cancer. In particular, an analysis of 87,785 patients with brain cancer diagnosed between 2000 and 2016 at the US National Cancer Institute showed that 29 patients (0.03%) died by suicide and 33,993 (38.7%) died from cancer and other causes within the first year after diagnosis. Patients with MNs who died by suicide were men (27–93.1%) over 44 years of age (24–82.8%), white (26–89.9%), and had glioblastoma (18–62.1%) [21]. The works of foreign authors indicated that a fourfold risk of suicide compared to the general population and a twofold risk compared to other oncological diseases was found in patients with brain and neck tumors [22]. A following clinical case is mentioned in literature: a patient suffering from malignant glioma of the brain committed self-mutilation (numerous chest wounds reaching 7 cm of depth) due to the manifestation of psychotic symptoms [23]. Some authors emphasized that an increased tendency to suicide may be based on the brain pathways affected by the tumor localization and by surgical routes [24]. One way or another, the tumor process inevitably affects the activity of brain neurotransmitters. Changes in brain structures and functions, such as a decrease in the number of neuronal cells, density and size, as well as a decrease in the thickness of the cortex and changes in synaptic circuits, may be associated with major depressive disorder, stress, and suicidal behavior [25]. Probably, histopathological tumor processes may affect the actualization of suicidal thoughts and attempts. For instance, a diagnosis of glioblastoma is more often associated with an increased risk of suicide than other types of tumors [26]. Surgical intervention in patients with low-grade glioma was due to a high risk of developing suicidal thoughts [27]. Although the cause of the development of suicidal forms is unclear, suicidal behavior in oncological diseases remains relevant in subsequent periods of life. It is believed that patients with MNs are more likely to have suicidal thoughts than suicide attempts or completed suicides. At the same time, the main problem for patients with brain cancer is that the disease leads to physical, mental, and spiritual stress. These factors are superimposed on predisposing personality characteristics and can lead to depression and suicide [28]. The assumptions about the risk of suicide with tumor damage to the frontal lobes [29] were not confirmed, which is probably due to the organization and implementation of the research methods.

Lung cancer is also a diagnosis associated with a high risk of suicidal behavior. In other words, the suicide rate in patients with lung cancer is higher than in the general population, and the risk is also almost twice as high as in other cancer sites combined [30]. The suicide rate was most often recorded in men in European countries. As a rule, this risk was associated with smoking and drinking, chronic hepatitis B and C, and premorbid mental problems [31]. In addition, it was found that the frequency of suicidal thoughts was higher in males than in females. Suicidal attempts were made by individuals with mental disorders [32], and they more often committed brutal forms of suicide (self-hanging) [33]. At the same time, there are studies illustrating a higher level of suicidal attempts in lung cancer in women (especially suicidal thoughts) compared to men [34]. The frequency of suicidal thoughts increases with the progression of the disease; the prevalence of suicidal thoughts in women is explained by a higher stress resistance to negative manifestations and life events [35]. Suicidal thoughts are, to some extent, a specific sign of suicidal attempts in lung cancer. In patients with lung cancer, the frequency of suicidal thoughts is higher than in patients with other types of cancer [36] and is 22.68% [35]. On the one hand, the severity of the disease and its symptoms (shortness of breath, fatigue, pain and nausea, loss of body weight and appetite) contribute to an increased risk of suicide [37]. On the other hand, a high level of suicides is also noted among lung cancer patients with a favorable prognosis [38].

Unfortunately, information on the reasons of increased suicide risk among lung cancer patients is only limited. It is suggested that the main reason is the lack of psychological support and empathic communication from health care workers, possibly due to temporary restrictions on working hours and a shortage of specialists. A low level of knowledge about specific risk factors for suicide cannot be ruled out [39].

The risk of suicide increases with gastric cancer – according to official statistics, it is approximately four times higher than in the general US population. Moreover, in women with gastric cancer, the suicide rate is eight times higher than in the general female population [40]. At the same time, in patients with gastric cancer of both sexes aged over 50 years, the likelihood of suicide was high [41]. Moreover, the risk of suicide is the highest during the first three months after diagnosis [42]. The cause of suicidal thoughts in gastric cancer is psychological stress in overcoming frustrating situations [43]. However, there are claims that the psychological aspect of the problem has not been sufficiently studied [44]. Other studies have found that 131 of 378 gastric cancer survivors (34.7%) had suicidal thoughts. They were significantly associated with patients' income, comorbidities, smoking, and general health. Suicidal thoughts are associated with symptoms (fatigue, nausea, vomiting, shortness of breath, loss of appetite, constipation, diarrhea, food restrictions, anxiety, dry mouth, hair loss, and also with existentialism) [45]. Since the vast majority of suicides in patients with gastric cancer occur within the first year after diagnosis, early detection and treatment of people at risk are of paramount importance [40].

Undoubtedly, identifying scientifically proven risk factors associated with suicide among patients with gastric cancer is a key point in developing a screening tool and a strategy for psychopharmacotherapeutic and psychotherapeutic intervention. Targeted and improved screening and identifying patients with gastric cancer as a separate group, based on suicide risk factors, will significantly reduce the incidence of suicide in this case.

The researchers believe that suicide in patients with prostate cancer is a common condition that can occur even many years after diagnosis (men are at risk of suicide 15 years or more after diagnosis of prostate cancer). In other words, the risk of suicide may actually shift from the secondary psychological impact of the diagnosis of cancer (short-term) to possibly long-term side effects or suffering as a result of treatment or the general aging process. Therefore, at all stages of dispensary observation and treatment, it is necessary to take into account predictors of suicide mortality, especially in individuals with increasing age, unmarried, without surgical treatment, and with metastatic disease. Up to 5–12% of patients with this diagnosis may have suicidal tendencies. The authors of the mentioned study supported their findings with three population studies; one of them reflects the prevalence of suicidal attempts in various MNs of the genitourinary system. In particular, the suicide risk was significantly higher in patients with high-grade prostate cancer (with adenocarcinoma according to the Gleason scale from 8 to 10), locally advanced cancer (stage T3 and T4 according to the TNM classification), and distant metastases. Further, the risk of suicide was associated with the characteristics of treatment, worsening somatic status, progressive anemia, and chronic pain syndrome. Based on the data obtained, the authors concluded that a higher risk of suicide was detected in men with prostate cancer compared to the general population [46]. Notably, metastatic forms of prostate cancer allow the five-year survival of about 28%, and with early detection of prostate cancer, the five-year survival is approximately 100% [47].

Suicidal behavior is also more common in patients with gynecologic cancer than in the general population. In particular, among 252,235 patients observed for 1,207,278 person-years, the suicide rate was 8.3 per 100,000 person-years with a standardized mortality rate of 1.4 (95% confidence interval 1.2–1.7; p<0.001). High rates of various forms of suicidal behavior were found in patients with ovarian cancer and during the first year after diagnosis. The risk of suicide was associated with younger age at diagnosis, high severity of the disease, and absence of surgical intervention [48]. Data are provided, revealing that suicidal behavior depends on the type of gynecologic cancer. Women with ovarian cancer had a higher risk of suicide and death due to an accident than the group without cancer. In addition, patients with type II epithelial ovarian cancer and patients diagnosed with well-differentiated non-metastatic cancer and pelvic exenteration were included in the group of increased suicide risk [49].

Thus, the conducted theoretical analysis of scientific research revealed a significant prevalence of suicidal behavior in cancer patients.

Notably, to date, no specific scientifically based guidelines for the prevention of suicide and suicidal thoughts among cancer patients exist. Moreover, in practice, the doctor conducts a survey regarding anxiety, depressed mood, and the use of psychoactive substances. Suicide risk is diagnosed in exceptional or obvious (urgent) cases. At the same time, suicidal tendencies are twice as high in cancer patients than in the population as a whole.

Thus, the following conclusions were made:

- suicidal activity in the structure of cancer diseases remains very high and fluctuates within wide limits (from 0.2% to 93.1%);

- suicidal behavior is most common in patients with brain cancer, lung and bronchial cancer, gastric cancer, prostate cancer, and gynecological cancer;

- the relationship between suicidal behavior and cancer is confirmed mainly by population studies;

- there is a significant gap in the research on establishing the cause-and-effect relationships between suicidal behavior and the abovementioned diseases; on suicidogenesis mechanisms and risk factors;

- the overwhelming majority of studies on suicidal behavior in cancer patients are limited to statistical data on suicidal behavior prevalence;

- the period of increased suicidal risk is 2 months – 1 year after diagnosis;

- in oncology patients, the predominant forms of suicidal behavior are suicidal thoughts and self-poisoning;

- psychological and social stress factors are significant in the formation of suicidal behavior in cancer patients;

- studies on the psychological, clinical-psychopathological, and clinical-dynamic aspects of suicidal behavior in cancer patients are practically non-existent.

Having summarized the literature data, the following preventive strategies can be formulated:

All of the above predetermines the need for scientific research into the problem of suicidal behavior while studying clinical-psychological, clinical-psychopathological, and clinical-dynamic features of suicidal behavior in oncology patients.