1. Introduction
Cancer-related fatigue is a pervasive and debilitating symptom experienced by many colorectal cancer (CRC) patients, which can persist for months or even years after primary cancer therapy [
1]. Besides fatigue, CRC survivors also commonly report other symptoms, such as depression, anxiety, pain, sleep disturbance, digestive tract symptoms, and sexual dysfunction [
2,
3,
4]. These symptoms stem from the physical and psychological sequelae of CRC and its treatments.
Chemotherapy is one of the vital treatment components in stage II or III CRC patients. However, the inherent nature of chemotherapy results in not only the destruction of cancer cells but also the damage to healthy cells, leading to various adverse effects [
5]. CRC patients undergoing chemotherapy experience adverse effects that impact their physical health, overall quality of life [
4,
5,
6], and emotional state [
6]. A study from Australia examining the adverse effects of chemotherapy in routine care found that CRC patients had the highest prevalence of fatigue (88%), with 89% of CRC patients having at least one adverse effect [
7].
Radiotherapy has become an integral part of managing rectal cancer, contributing to a significant reduction in the rate of local recurrences when paired with total mesorectal excision surgery in stage II and III CRC patients [
8]. Notably, neoadjuvant radiotherapy, administered before surgery, has been associated with lower local recurrence rates and fewer toxic effects than adjuvant therapy given after the operation [
9]. While radiotherapy is an effective treatment strategy for rectal cancer, it is not without potential side effects due to the impact on surrounding organs. Locally, patients may experience diarrhea, frequent urination, gas and bloating, cramping, skin irritation, and constipation [
10]. In addition, systemic side effects like fatigue and loss of appetite might significantly impact the patient’s well-being [
11].
Previous studies have reported that multiple symptoms cluster together in CRC survivors, suggesting that these symptoms may be interconnected and share underlying mechanisms [
12]. For example, one study identified four distinctive symptom clusters (psychological, digestive and urinary, low energy, and pain) in CRC patients during the first year after surgery [
13]. Functional status and quality of life are often significantly impaired among CRC survivors who experience these adverse symptoms simultaneously [
14,
15]. Therefore, modifying the traditional single-symptom approach and addressing symptom clusters when treating CRC patients might be beneficial.
Return to work of cancer patients is an essential milestone in rehabilitation after primary treatment. Patients who return to work report regaining a sense of normalcy and purpose, which is closely linked to the ability to provide for oneself and economic independence [
16,
17]. However, only 57% of cancer patients have been reported to return to work after treatment [
18]. The symptoms of primary disease and adverse effects stemming from associated treatments often form significant barriers to resuming professional activities. Fatigue and depression can cause decreased productivity, while physical symptoms lead to lower employment rates [
19]. Therefore, the challenges do not solely arise from the cancer diagnosis but are also intricately related to the treatment side effects, further complicating the patient’s ability to reintegrate into the pre-diagnosis work environment.
As fatigue commonly co-occurs with various adverse effects of CRC treatment, it is crucial to investigate the association between adverse symptoms and persistent cancer-related fatigue and low ability to work with a longitudinal study design. With a better understanding of the temporal relationship, it can be better estimated whether such adverse symptoms are causally related to fatigue and ability to work or are simply bystanders of the associations of CRC treatments and fatigue.
The first aim of this study was to determine whether there are clusters of symptoms in CRC patients undergoing in-patient rehabilitation. The investigated symptoms include psychological, physical, and fatigue-related symptoms and issues impacting daily life and social interactions. The second aim was to explore which of these symptoms are also associated with changes in fatigue and the ability to work in the first three months after rehabilitation.
4. Discussion
The primary objective of this study was to identify symptom clusters in CRC patients within a year of completing primary CRC treatment using exploratory factor analysis. The second aim was to investigate which symptoms were longitudinally associated with the change of fatigue or ability to work from baseline to the 3-month follow-up using multivariable linear regression. We have identified six symptom clusters: fatigue, gastrointestinal symptoms, pain, psychosocial symptoms, urinary symptoms, and chemotherapy side effects clusters. Out of 30 symptoms with significant factor loadings, 14 symptoms were longitudinally associated with fatigue and 24 symptoms with the ability to work.
The fatigue cluster consisted of the following symptoms: fatigue (FACIT-F-FS), interference with daily life, emotional fatigue, depression, cognitive fatigue, dyspnea, social sequelae, appetite loss and ability to work. Fatigue is one of the most frequent symptoms of CRC patients, caused by primary disease or affiliated treatment. It is characterized as “
physical, social and/or cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with functioning “[
31], and all of the symptoms included in this cluster, apart from dyspnea, could be interpreted as manifestations of cancer-related fatigue. Lack of appetite has been identified as a correlate of cancer-related fatigue [
32]. Dyspnea, or the feeling of difficulty breathing, could be present during everyday physical activities such as walking or climbing the stairs. Cancer-related anemia, often present in CRC patients due to the chronic character of the disease or occult bleeding, can be a cause of both dyspnea and fatigue [
33]. The fatigue cluster was often identified in previous studies on symptom clusters, irrespective of the type of malignancy [
13,
34]. In a network analysis of symptom clusters among a diverse group of cancer survivors, fatigue emerged as the most central symptom across all networks [
35]. This finding highlights the crucial need to address fatigue early in the rehabilitation process.
The gastrointestinal symptoms cluster consisted of fecal incontinence, stool frequency, sore skin, embarrassment, diarrhea, flatulence, and blood/mucus in stool. Most of these symptoms can be directly linked to treatment side effects. Local radiotherapy can cause diarrhea, bloating, skin erythema, and fecal incontinence [
10]. Due to the nature of these symptoms, patients can have accompanying embarrassment in social settings. The gastrointestinal symptoms cluster, often characterized as “digestive symptoms cluster”, is frequently identified in previous literature in CRC patients [
13,
36] and patients with other cancer types [
35].
The pain cluster consisted of pain, abdominal pain, buttock pain, bloating, and dysuria. Pain is one of the symptoms present at the time of the diagnosis and before treatment and can often be aggravated by subsequent treatments [
37]. Oxaliplatin-induced neuropathy has emerged as a common side effect of chemotherapy for CRC patients [
38]. Chronic pain can be a long-term side effect of CRC surgery. A Danish study found that 40% of CRC patients reported having chronic abdominal or pelvic pain after rectal surgery [
39]. The pain cluster is commonly identified in cancer populations, irrespective of tumor localization [
13,
15,
40].
The psychosocial symptoms cluster consisted of anxiety, financial difficulties, and psychosocial distress. During therapy, many patients need to take an absence from work. A previous study in the Netherlands found that CRC patients had a median return-to-work time of 423 days from the beginning of their absence leave [
41]. The temporary absence from work can be a cause of financial difficulties as well as worry and anxiety for CRC patients. Anxiety is also frequent at the start of the treatment and can persevere after the completion of the treatment [
42]. In some previous studies, anxiety has clustered with depression and other emotional symptoms [
36,
43]. However, in our study, anxiety coupled with psychosocial distress and financial difficulties. It is possible that the absence from work and its financial implications may have amplified the interconnectedness of anxiety, financial strain, and broader psychosocial distress in CRC patients in our study.
The urinary symptoms cluster consisted of urinary incontinence, urinary frequency, and sleep disturbance. Sleep disturbances are not unusual in patients with frequent urination during the night. A previous study found that late urinary side effects affect up to 41% of CRC patients following brachytherapy for colorectal cancer. Symptoms included obstructive and irritative symptoms [
44]. The urinary symptoms have been described in previous studies of CRC symptom clusters.
The chemotherapy side effects cluster included nausea or vomiting, taste alteration, constipation, and hair loss. These symptoms have been described as common post-chemotherapy side effects in the literature [
45]. Though nausea and vomiting are sometimes grouped as a gastrointestinal cluster in previous literature [
46], they constitute their own cluster alongside other prevalent chemotherapy side effects in our study. These findings indicate the complexity of CRC symptomatology after treatment and variability in patient experience.
In the context of our findings, we identified six specific symptom clusters in CRC patients. Our findings point that these clusters originate from the primary disease or, more predominantly, from therapeutic interventions. Notably, the fatigue and pain clusters, which are prominently present, suggest an underlying inflammatory mechanism, a facet that requires further exploration [
47]. A recent study further supports this hypothesis by reporting an association between the symptom clusters in palliative CRC patients and proinflammatory cytokines [
48]. This underscores the necessity to investigate potential inflammatory mechanisms underlying these symptom clusters, emphasizing the importance of ongoing research for improved management and comprehension of CRC-associated symptoms.
In this study, we identified two groups of symptoms to be longitudinally associated with fatigue: gastrointestinal/physical symptoms (fecal incontinence, stool frequency, urinary incontinence, abdominal pain, dyspnea, and nausea or vomiting) and psychosocial symptoms (cognitive fatigue, embarrassment, anxiety, financial difficulties, and sleep disturbance). Participants who experienced any of these symptoms were more likely to have higher fatigue levels. Gastrointestinal symptoms in female CRC patients were previously shown to be associated with fatigue, as well as reduced social functions and increased daily life interference [
49]. Considering psychosocial factors, a cross-sectional study identified an association between fatigue and both sleep disturbances and anxiety in CRC patients [
50]. However, while this study noted a significant relationship between fatigue and depression, our findings did not corroborate this link. Possible reasons for this inconsistency might include variations in study methodologies, patient demographics, or therapeutic regimens between the two studies. Recognizing symptoms associated with fatigue is crucial for clinical practice, allowing for more targeted interventions in fatigue management for CRC patients.
We have found 24 symptoms that are longitudinally associated with the ability to work. Our findings confirm the results from the systematic review on the influence of cancer-related symptoms on the ability to work [
19]. Previously, a study found that CRC patients had a 56% higher risk of losing employment due to work disability up to 4 years after CRC diagnosis, compared to the general population [
51]. Symptoms related to lower ability to work stemmed from all six of the identified clusters. Out of 11 symptoms associated with improved fatigue at the 3-month follow-up, 9 were also associated with improved ability to work in the first 3 months after rehabilitation. These results reaffirm the pleiotropic influence of different symptoms on the ability to work in CRC patients, apart from the conventional predictors such as age and stage of the disease. It also underscores the importance of a holistic approach, emphasizing the need to address the entirety of symptoms rather than the traditional one-symptom focus. Understanding the clustering of symptoms and its connection to the ability to work is a central step in developing intervention strategies that could be implemented during the rehabilitation part of the convalescence of CRC patients.
The MIRANDA study possesses several strengths. Firstly, it’s a multicentric, prospective cohort study that aims to capture data from six rehabilitation clinics across different regions in Germany, ensuring a diverse and representative sample. The rigorous inclusion and exclusion criteria further ensure the consistency and reliability of the data. The study involves periodic follow-ups, which allows for a longitudinal understanding of the variables in question, such as fatigue and the ability to work. Furthermore, the study utilizes multiple well-established scales and questionnaires like the FACIT-F-FS, GDS-15, GAD-7, and EORTC-QLQ-C30, among others, to comprehensively assess various symptoms and factors.
However, there are some inherent limitations to our study. One limitation is the reliance on self-reported data for most sociodemographic, lifestyle, and clinical information, such as symptom presence. Only a few variables, such as weight, height, and stage of the disease, relied on physician reports. Additionally, the ability to work was estimated using a single-item measure. Various factors can influence the ability to work, including physical symptoms, cognitive function, environmental conditions, and social and emotional well-being. A single item might not capture all these dimensions. Lastly, almost half of the participants were recruited during the COVID-19 pandemic between Sept 2020 and Dec 2021. Consequently, there is a possibility that some of these participants might have experienced post-COVID symptoms or late effects from the virus infection [
52]. This could potentially increase the prevalence of certain symptoms in our sample, making it higher than it might have been in a non-pandemic context.
Author Contributions
Conceptualization, B.S.; methodology B.S. and T.V., H.B., R.C.; validation, T.V., M.S., and B.S.; formal analysis, T.V. and B.S.; investigation, R.C., B.B., H.F.; data curation, B.B., H.R. M.S.; writing—original draft preparation, T.V., and B.S.; writing—review and editing, B.S., T.V., R.C., B.B., H.F., M.S., and H.B.; visualization, T.V., B.S., and R.C.; supervision, H.B., and B.S.; project administration, B.S., H.B., M.S.; funding acquisition, H.B., R.C., and B.S. All authors have read and agreed to the published version of the manuscript.