Study design
The researchers conducted a cross-sectional, descriptive correlational study to investigate factors affecting women undergoing chemotherapy for breast cancer. This type of study design was chosen to capture information of the variables of interest and to determine relationships among them without manipulating any variables.
Study setting and population
The study was carried out among women undergoing chemotherapy for breast cancer referred to selected hospitals and outpatient oncology clinics located at the Arian Clinic, in Amol city, Mazandaran Province, northern Iran. These healthcare centers were selected based on their patient volume and accessibility to ensure a representative sample of the regional population. Data collection was conducted over a six-month period, from July to December 2024.
Inclusion criteria
Participants were selected based on the following inclusion criteria: (i) female patients aged 18 years and older, (ii) histologically confirmed non-metastatic breast cancer (Stages I–III), (iii) patients who were either currently receiving or scheduled to receive chemotherapy treatment, (iv) provided informed consent for participation in the study.
Exclusion criteria
Patients were excluded from the study if they met any of the following conditions: i: presence of significant psychiatric disorders (such as major depression, bipolar disorder, or schizophrenia), ii) diagnosis of non-cancer-related chronic conditions that could independently affect the study outcomes (e.g., severe anemia, chronic pain syndromes), iii) concurrent use of medications known to impact sleep or psychological well-being, such as sedatives, antipsychotics, or stimulants, iv) employment involving night-shift work, as such work schedules can independently disrupt circadian rhythms and sleep patterns, thus confounding the study findings.
Sampling technique and sample size
This study included 468 women with breast cancer undergoing chemotherapy, recruited through convenience sampling due to feasibility constraints in a single-center setting and to maximize participation during treatment visits. The required sample size was calculated using G*Power software version 3.1.9.7, based on a two-tailed test, an alpha of 0.05, a power of 0.90, and a correlation coefficient of 0.16 from a previous study [16]. The minimum sample size was determined to be 406. To account for potential dropouts or incomplete data, a 15% increase was applied, resulting in a final target of 467 participants.
Research instruments
The data collected included demographic information (age, marital status, occupation, place of residence, education level, economic status, family history of illness, and duration of cancer), quality of life according to the EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer), insomnia according to the Insomnia Severity Index Questionnaire (ISI), and patients’ attitudes and beliefs according to the Cancer Attitude and Belief Questionnaire.
EORTC QLQ-C30
The quality of life (QoL) of women undergoing chemotherapy for breast cancer was evaluated via the EORTC QLQ-C30 (version 3), which consists of 30 items across three subscales: global health status/QoL; functional scales (covering physical, role, cognitive, emotional, and social aspects); and symptom scales (covering fatigue, pain, nausea/vomiting, insomnia, etc.) [17]. The global health/QoL assessment used a 7-point Likert scale, whereas the symptom and functional items used a 4-point scale. According to the EORTC standards [18], scores were also converted from 0 to 100 and interpreted so that higher functional/global scores denoted better outcomes and higher symptom ratings denoted greater burdens. Excellent reliability was demonstrated by the validated Persian adaptation [19, 20]. In this study, the reliability of this questionnaire was assessed via the calculation of Cronbach’s alpha coefficient and was reported as 0.88 for overall quality of life.
Insomnia severity index questionnaire (ISI)
The Insomnia Severity Index (ISI) was used to assess the level of insomnia. The ISI questionnaire contains seven items, which include difficulty in starting sleep and problems with staying asleep (waking up at night and waking up early in the morning), satisfaction with the current sleep pattern, and interference with daily functioning. The questionnaire helps to evaluate the severity of the damage attributed to the sleep problem and the degree of confusion or worry caused by the sleep problem and is estimated on a 5-point Likert scale (0 = never and 4 = very much). The total score (0–28) of this questionnaire was categorized as follows: 0–7 = clinically significant insomnia, 14–8 = below the clinical threshold, 21–15 = moderate clinical insomnia, and 28–22 = severe clinical insomnia [21]. The validated Persian-translated version of the ISI is highly valid and reliable [22, 23]. The present study’s internal consistency with this research tool was similarly good (α = 0.80).
Cancer attitude and belief questionnaire
The researchers assessed attitudes and beliefs toward cancer via the questionnaire developed by Cho et al., which consists of 12 items in three domains: (a) impossibility of recovery; (b) stereotypes; and (c) discrimination, each with four questions related to the impossibility of recovery, stereotypes, and discrimination. The data were collected via a Likert scale (1 = completely disagree, 2 = disagree, 3 = agree, and 4 = completely agree). After the scores of the questions were summed, a total score between 12 and 48 was obtained. The higher the participants’ scores for each dimension are than the mean values are, the more negative the attitude toward cancer and the greater the degree of stigma [24]. In a study by Shervin Badihian, the internal consistency of the questionnaire items in the study sample was satisfactory, with Cronbach’s alpha coefficients for the impossibility of recovery, stereotypes, and discrimination of 0.67, 0.38, and 0.66, respectively [25]. In the present study, the internal consistency of this research tool was similarly good: 0.70, 0.85, and 0.72.
Data collection procedure
After receiving a permission letter from the research committee and head of institution, the researcher collected samples from women undergoing chemotherapy for breast cancer as the research population. The researchers used a convenient sampling method to choose participants after informed consent was obtained from the research participants. Each participant was thoroughly informed about the study’s objectives and procedures, with clear assurances regarding the protection of their anonymity and the confidentiality of their data. Additionally, they were explicitly made aware that their participation was entirely voluntary and that they could withdraw from the study at any time without any negative consequences. Following this, self-administered questionnaires were distributed to a total of 468 participants. To facilitate data collection, three trained researchers were assigned to the task. These researchers underwent comprehensive training covering the study’s objectives, methodology, inclusion and exclusion criteria, and ethical considerations. Moreover, the training sessions included instructions on how to collect data from illiterate participants data collection and these researchers assisted illiterate participants in completing questionnaires.
Statistical analysis
The data were analyzed with IBM SPSS (Statistical Package for the Social Sciences) version 24 statistical software. Data normality was evaluated via kurtosis, skewness and Q-Q plots. Nonparametric tests (Gamma/Cramer’s) were used for skewed data. Descriptive statistics (frequency, percentage and mean) were used for demographic variables. Gamma and Cramer’s correlation coefficients were employed to determine the relationships between variables (insomnia, QoL, and attitudes/beliefs toward cancer). The rank logistic test was used to investigate the predictors of the variables. P values less than 0.05 were regarded as statistically significant.