Clinicopathological and molecular landscape of 5-year IDH-wild-type glioblastoma survivors: A multicentric retrospective study

Five-year glioblastoma (GBM) survivors (LTS) are the minority of the isocitrate dehydrogenase (IDH)-wild-type GBM patients, and their molecular fingerprint is still largely unexplored. This multicenter retrospective study analyzed a large LTS-GBM cohort from nine Italian institutions and molecularly characterized a subgroup of patients by mutation, DNA methylation (DNAm) and copy number variation (CNV) profiling, comparing it to standard survival GBM. Mutation scan allowed the identification of pathogenic variants in most cases, showing a similar mutational spectrum in both groups, and highlighted TP53 as the most commonly mutated gene in the LTS group. We confirmed DNAm as a valuable tool for GBM classification with a diagnostic refinement by using brain tumor classifier v12.5. LTS were more heterogeneous with more cases classified as diffuse pediatric high-grade glioma subtypes and having peculiar CNVs. We observed a global higher methylation in CpG islands and in gene promoters of LTS with methylation levels of distinct gene promoters correlating with prognosis.

Psychosocial factors associated with workability after surgery in cancer survivors: An explorative study

This study aimed to evaluate the work ability and its associated factors in patients with glioma (II, III) and breast cancer after 6 (T0) and 12 (T1) months from surgery. A total of 99 patients were evaluated with self-reported questionnaires at T0 and T1. Correlation and Mann-Whitney tests were used to investigate the association between work ability and sociodemographic, clinical, and psychosocial factors. The Wilcoxon test was used to investigate the longitudinal change in work ability. Our sample showed a decrease in work ability level between T0 and T1. Work ability was associated with emotional distress, disability, resilience, and social support in glioma III patients at T0, and with fatigue, disability, and clinical treatments in patients with breast cancer at T0 and T1. Work ability levels decreased in patients with glioma and breast cancer and were associated with different psychosocial factors after surgery. Their investigation is suggested to facilitate the return to work.

Isocaloric Ketogenic Diet in Adults with High-Grade Gliomas: A Prospective Metabolic Study

The use of the ketogenic diet (KD) as an adjuvant therapy in high-grade gliomas (HGG) is supported by preclinical studies, but clinical data on its effects on metabolism are currently lacking. In this study, we describe the effects of a KD on glucose profile, ketonemia, energy metabolism, and nutritional status, in adults affected by HGG. This was a single-arm prospective study. An isocaloric 3:1 KD was administered for 1 mo. Glucose profile was assessed by using fasting glycemia, insulin, and glycated hemoglobin. To evaluate ketonemia changes, a hand-held ketone meter was used from home. Energy metabolism was assessed by indirect calorimetry. Nutritional status was evaluated through changes in body composition and in lipid and hepatic profile. No changes in fasting glycemia were observed; however, insulinemia dropped to half of baseline levels. The KD shifted the metabolism, rising ketonemia and decreasing glucose oxidation rate to a quarter of the initial values. Moreover, the KD was generally safe. One-month intervention with the KD was able to act upon key metabolic substrates potentially involved in HGG metabolism. The lack of a significant reduction in fasting glycemia should be investigated in future studies.

Employment and Work Ability of Persons With Brain Tumors: A Systematic Review

Brain tumors (BT) are between the eight most common cancers among persons aged 40 years, with an average survival time of 10 years for patients affected by non-malignant brain tumor. Some patients continue to work, reporting difficulties in work-related activities, or even job loss. The purpose of the present study was to review the existing information about the ability people with BT to return to work and to identify factors associated with job loss. We performed a systematic review on SCOPUS and EMBASE for peer-reviewed papers that reported studies assessing work ability in patients with BT that were published in the period from January 2010 to January 2020. Out of 800 identified records, 7 articles were selected for analysis, in which 1,507 participants with BT were enrolled overall. Three main themes emerged: the impact of neuropsychological functioning on work productivity, the change of employment status for long-term survivors and issues related to return to work processes. Based on the results of selected studies, it can be concluded that the impact of BT on workforce participation is determined by depressive symptoms and cognitive deficits, as well as by high short-term mortality but also on environmental barriers. Vocational Rehabilitation programs should be implemented to help patients wishing to return to or maintain their current work, as much as possible.

Anthropometrics and Body Composition in Adults with High-Grade Gliomas: Effects of Disease-Related Variables

Nutritional status in adults with high-grade gliomas (HGGs) has been poorly investigated. We studied anthropometrics and fat mass (FM), fat free mass (FFM), and body water in HGGs patients also in relation to disease-related variables. Fifty-one patients (17 III and 34 IV-grade) and fifty-one control group (CG) matched for sex, age, and BMI were enrolled. Neurological scales, anthropometry, bioimpedance, and blood sampling were performed and analyzed according to grade, lesion location, extent of resection, phase of treatment, current steroids and antiepileptic therapy, and age of patient. 41.2% were overweight and 15.7% obese. Compared to the CG, HGGs had similar anthropometrics and body composition. IV-grade, compared to the III, had higher BMI, waist circumference, FM and lower FFM. Only patients during concomitant radio and chemotherapy showed a negative BMI variation from baseline. In conclusion, overnutrition occurs in almost 6 out of 10 HGGs patients and is more relevant in IV-grade. Throughout all the treatment phases, there is a higher risk of weight loss occurred only during concomitant radio and chemotherapy. Body composition showed no specific features compared to controls. These results may assist intervention studies directed towards neurometabolic dietary treatment. Nutritional screening is warranted during the time course of disease.

Caring for Brain Tumour Patients: Psychological Reactions After Bereavement

Aim

The aim of this study was to describe the changes in quality of life and in levels of anxiety and depression experienced by caregivers of patients with brain tumour 18 months after their bereavement.

Methods

This longitudinal study employed data from two time points: time 1, during the hospital stay of the caregiver's loved one; and time 2, approximately 18 months after the death of the patient. A total of 51 caregivers agreed to participate in the study at both time points. We used the Hospital Anxiety and Depression Scale and the 36-Item Short Form Health Survey; we compared the data obtained at the two time points using the paired-samples t-test.

Results

Caring for someone with a brain tumour had a greater impact on the caregivers’ mental health than on their physical well-being. At time 2, the caregivers’ levels of anxiety and depression and psychological burden were decreased, indicating that they were in a better emotional state than they had been in time 1. However, the mean values in the depression, vitality, and mental health subscales were lower than those in the normative data, indicating that these caregivers had a worse psychological status than members of the normative group.

Conclusion

Our study underscores the necessity of supporting caregivers and monitoring their suffering levels; such suffering can compromise their social and work lives, not only during the disease trajectory but also in bereavement. Providing psychological and emotional support for caregivers of patients with brain tumour during both periods could lessen the suffering and unhappiness of these caregivers.

Psychological features and quality of life in 50 adult patients with epilepsy and their caregivers from the Lecco epilepsy center, Italy

Epilepsy is one of the most common neurological disorders. To the best of our knowledge, in Italy, the relationship between patients' and caregivers' psychological state has rarely been analyzed. Thus, we sought to evaluate both the psychological state of patients with epilepsy and that of their caregivers and the interrelationship between them. We also assessed the existing relation between psychological features and some clinical and demographic information, such as number of antiepileptic drugs (AEDs), epilepsy duration and education level of patients and their caregivers. We enrolled in the study 50 consecutive adult patients attending the epilepsy clinic of "A. Manzoni" Hospital and their caregivers. Both patients and their caregivers were administered Hospital Anxiety and Depression Scale (HADS) and 36-item Short-Form Health Survey (SF-36). Anxiety, depression and quality of life values of both patients and their caregivers did not differ significantly from the normative samples. No statistically significant correlation between epilepsy duration and patients' and caregivers' psychological features was found. Patients which took more than one AED reported lower values of "Vitality" (p <.05) and "Social Functioning" (p <.05) than their own caregivers. Caregivers with higher education level presented lower "Vitality" values than caregivers with lower education level (p <.05). Patients with pharmacoresistant seizures reported lower values of "Mental Health" than patients with non-pharmacoresistant seizures (p <.05). In this context, the role of coping mechanisms by patients and caregivers may explain apparently unexpected findings and suggests that strategies aimed at reinforcing them may be effective in selected cases. Therefore, while the severity of epilepsy may have an impact on the psychological state of adult patients with epilepsy and their caregivers, our results highlight the role of multidimensional determinants, including stigma. Further studies are needed to identify the factors related to epilepsy, patients, caregivers, treatments, and the environment that may be modifiable in order to improve self-perceived QoL.

Needs of neuro-oncological patients and their caregivers during the hospitalization and after discharge: results from a longitudinal study

PURPOSE

The aims of this study are to identify neuro-oncological patients' and their caregivers' needs during hospitalization (T0) and at 4 months after discharge (T1); to analyze the longitudinal changes in patients' and caregivers' needs and burden; to identify correlations between patients' needs and caregivers' burden and needs.

METHODS

A pilot observational longitudinal study was conducted on 94 neuro-oncological patients and their caregivers using NEQ to evaluate patients' needs, CNA, and FSQ for caregivers' needs and burden at T0 and T1. Descriptive statistics were performed to illustrate the distribution of questionnaires' scores. The longitudinal change of NEQ, FSQ, and CNA scores were investigated using Wilcoxon test. Spearman's correlation was used to measure the relation between NEQ and FSQ and CNA scores.

RESULTS

The most frequent patients and caregivers' needs were material and informative. Needs tend to decrease over time; in particular FSQ factor "need for knowledge about the disease", CNA factor "Information/communication needs" and CNA total score significantly decreased (p < 0.001). NEQ total score significantly correlated with FSQ factors "emotional burden" and "need for knowledge about the disease" and CNA total and factors scores at T0 and T1. At T0, NEQ correlated significantly with FSQ factor "thoughts about death", while at T1, it correlated with FSQ factor "problems in social involvement".

CONCLUSIONS

It is crucial to plan an assessment of patients' and caregivers' needs from the very beginning, in order to identify those individuals potentially at risk of developing high level of distress and to provide information and support following the illness trajectory of the brain tumor.

Safety and efficacy of primary central nervous system lymphoma treatment in elderly population

Elderly patients represent an important subgroup in primary central nervous system lymphoma (PCNSL) that accounts for approximately half the cases. Furthermore age represents one of the heaviest prognostic factors and in some cases it has more effect on survival than therapies. We performed a retrospective analysis to assess the toxicity and the efficacy of high-dose methotrexate (HDMTX) chemotherapy in a PCNSL population older than 70 years. Seventeen consecutive immunocompetent patients older than 70 years, with histologically confirmed PCNSL, without systemic involvement, treated with HDMTX at our institution between May 2005 and April 2013, were retrospectively evaluated. Main outcome measures were acute toxicity and tumour response. No evidence of haematological toxicity was recorded in 47 % of patients and no deaths related to toxicity grade were reported. Patients achieved a partial response after 3 cycles of chemotherapy in 53 % of cases. The median overall survival (m-OS) from diagnosis was 20.9 months (range 5.2-34 months), with OS-12 of 58.8 % and an OS-24 of 45.4 %. Since there is no standard of care in the treatment of PCNSL in elderly population, it should be taken into account that elderly patients not always can be considered "fragile" and the general tendency to less treat to avoid severe toxicity should not be the rule.

Clinical management of grade III oligodendroglioma

Oligodendrogliomas represent the third most common type of glioma, comprising 4%-15% of all gliomas and can be classified by degree of malignancy into grade II and grade III, according to WHO classification. Only 30% of oligodendroglial tumors have anaplastic characteristics. Anaplastic oligodendroglioma (AO) is often localized as a single lesion in the white matter and in the cortex, rarely in brainstem or spinal cord. The management of AO is deeply changed in the recent years. Maximal safe surgical resection followed by radiotherapy (RT) was considered as the standard of care since paramount findings regarding molecular aspects, in particular co-deletion of the short arm of chromosome 1 and the long arm of chromosome 19, revealed that these subsets of AO, benefit in terms of overall survival (OS) and progression-free survival (PFS), from the addition of chemotherapy to RT. Allelic losses of chromosomes 1p and 19q occur in 50%-70% of both low-grade and anaplastic tumors, representing a strong prognostic factor and a powerful predictor of prolonged survival. Several other molecular markers have potential clinical significance as IDH1 mutations, confirming the strong prognostic role for OS. Malignant brain tumors negatively impacts on patients' quality of life. Seizures, visual impairment, headache, and cognitive disorders can be present. Moreover, chemotherapy and RT have important side effects. For these reasons, "health-related quality of life" is becoming a topic of growing interest, investigating on physical, mental, emotional, and social well-being. Understanding the impact of medical treatment on health-related quality of life will probably have a growing effect both on health care strategies and on patients.

Overlapping phenotypes in complex spastic paraplegias SPG11, SPG15, SPG35 and SPG48

Hereditary spastic paraplegias are a heterogeneous group of neurodegenerative disorders, clinically classified in pure and complex forms. Genetically, more than 70 different forms of spastic paraplegias have been characterized. A subgroup of complicate recessive forms has been distinguished for the presence of thin corpus callosum and white matter lesions at brain imaging. This group includes several genetic entities, but most of the cases are caused by mutations in the KIAA1840 (SPG11) and ZFYVE26 genes (SPG15). We studied a cohort of 61 consecutive patients with complicated spastic paraplegias, presenting at least one of the following features: mental retardation, thin corpus callosum and/or white matter lesions. DNA samples were screened for mutations in the SPG11/KIAA1840, SPG15/ZFYVE26, SPG21/ACP33, SPG35/FA2H, SPG48/AP5Z1 and SPG54/DDHD2 genes by direct sequencing. Sequence variants were found in 30 of 61 cases: 16 patients carried SPG11/KIAA1840 gene variants (26.2%), nine patients carried SPG15/ZFYVE26 variants (14.8%), three patients SPG35/FA2H (5%), and two patients carried SPG48/AP5Z1 gene variants (3%). Mean age at onset was similar in patients with SPG11 and with SPG15 (range 11-36), and the phenotype was mostly indistinguishable. Extrapyramidal signs were observed only in patients with SPG15, and epilepsy in three subjects with SPG11. Motor axonal neuropathy was found in 60% of cases with SPG11 and 70% of cases with SPG15. Subjects with SPG35 had intellectual impairment, spastic paraplegia, thin corpus callosum, white matter hyperintensities, and cerebellar atrophy. Two families had a late-onset presentation, and none had signs of brain iron accumulation. The patients with SPG48 were a 5-year-old child, homozygous for a missense SPG48/AP5Z1 variant, and a 51-year-old female, carrying two different nonsense variants. Both patients had intellectual deficits, thin corpus callosum and white matter lesions. None of the cases in our cohort carried mutations in the SPG21/ACP33 and SPG54/DDH2H genes. Our study confirms that the phenotype of patients with SPG11 and with SPG15 is homogeneous, whereas cases with SPG35 and with SPG48 cases present overlapping features, and a broader clinical spectrum. The large group of non-diagnosed subjects (51%) suggests further genetic heterogeneity. The observation of common clinical features in association with defects in different causative genes, suggest a general vulnerability of the corticospinal tract axons to a wide spectrum of cellular alterations.

Privacy-solidarity conflict: the communication with the support group

Actually guidelines require that patient must be informed about his condition so that he can choose the persons he wants to share these information with. Nonetheless, the caregiver usually gets an intermediary role in doctor-patient communication thus becoming the doctor's main conversation partner and claiming to be given more information than the patient himself. A more complex situation is about brain tumours patients sometimes affected by cognitive deficiencies, compromising their comprehension skills or their capability of keeping the information they are being given. A preliminary study allowed to submit separately to brain tumour patients and their family members a semi-structured interview. Although doctors communicate diagnosis and therapeutic plans, patients and their family members often do not seem to remember the information they are given. An important percentage of patients and their carers cannot tell correctly what they was said by the doctors. Only a minor percentage of patients do not want to know all details of their disease. Instead, most of the family members, would rather their beloved were given just partial information on their conditions or even not given information at all. Communication with patients and their carers requires careful re-negotiation in a multiple time-points, rather than a one-off communication episode.

Neuro-oncological diagnosis in patients without histological confirmation

The impossibility to conduct a histological diagnosis could be due to different reasons: (1) patient's refusal to undergo surgery/biopsy. (2) Technical difficulties: despite the advance in surgical procedures, the removal of lesions that are located either in critical or in deep areas represents a considerable risk for patients. (3) Quality/quantity of the sample. In rare cases even when the surgical sample is achieved it could be impossible to reach a histological confirmation, for example due to the small amount of tissue obtained. The lack of histology leads to suboptimal therapy, incorrect prognosis, and misinterpretation of clinical trials and furthermore undermines the possibility to perform most radiation and chemotherapy protocols. In this setting the morphological data obtained with conventional MR imaging may be integrated with the metabolic, structural and perfusional information provided by new MR and metabolic techniques (spectroscopy, SPECT, PET in particular).

Bevacizumab at recurrence in high-grade glioma

Bevacizumab has been introduced in the management of high-grade gliomas after preliminary studies that showed an acceptable safety and a marked increase in clinico-radiological responses in comparison with second-line chemotherapy. The objective is to synthetically review the present use of bevacizumab--alone or in combination--in the context of recurrent high-grade glioma and highlight the future developments. The methodology of this study is to analyse and discuss relevant literature studies using bevacizumab in recurrent high-grade glioma. Bevacizumab may be used as single-agent therapy in recurrent high-grade glioma, with good clinico-radiological responses having little effect on survival. The open questions and developments include new MRI criteria for evaluation of response to anti-angiogenic agents, the identification of putative factors predicting response/failure of bevacizumab and the introduction of bevacizumab in first-line management of high-grade glioma.

Malignant gliomas: early diagnosis and clinical aspects

Brain tumor symptoms vary greatly from person to person because of two factors: location and size of tumors. The size of a tumor, however, does not necessarily affect the severity of symptoms. Manifestations depend on the cause of the symptoms: an increase in ICP, direct compression of gray or white matter, shifting of intracranial contents, or secondary cerebral ischemia. Symptoms may be non-specific and include headache, altered mental status, ataxia, nausea, vomiting, weakness, and gait disturbance. Left-sided weakness may be seen in a patient with a tumor pressing on the contra-lateral motor strip or speech difficulties may occur if a tumor is in the dominant hemisphere. Up to a third of people report having seizures prior to being diagnosed with a brain tumor. Rarely, brain tumor can present with psychiatric symptoms but without other neurological signs or symptoms. Evaluation for brain tumor is indicated in any patient with chronic, persistent headache associated with protracted nausea, vomiting, seizures, changes in headache pattern, neurologic symptoms, and change in personality.

The burden of brain tumor: a single-institution study on psychological patterns in caregivers

Quality of life and well-being in caregivers are usually partly neglected since all attention is focused on patients and the way they react to the illness. Carers also usually neglect their own needs, especially when the illness of the patient is as complex as a brain tumor. The aim of this study is to investigate how caregivers deal with a diagnosis of brain tumor in their relatives and how they manage their quality of life and psychosocial well-being. One hundred primary caregivers of patients with brain tumors were interviewed and were asked to fill in self-administered questionnaires detecting multidimensional levels of quality of life, anxiety, depression, and psychosocial reaction to the patient's illness. Data were related with some functional and psychosocial information collected about the patient's disease. Caregivers try to react to the illness of their relatives by mobilizing their physical reaction and growing their self-esteem, but they live with a clinically significant impairment of their quality of life, and experience a deep level of anxiety and depression. The caregivers' burden appears mainly in their ability to provide care and in financial strain. The length of disease and the functional status of patients significantly influence caregivers' psychosocial well-being. Despite the appearance they want to show their affected relatives, caregivers suffer from deep limitation in their quality of life. The relevance of caregivers' burden suggests the importance of psychological support to improve reaction to the illness.

Salvage chemotherapy with procarbazine and fotemustine combination in the treatment of temozolomide treated recurrent glioblastoma patients

The purpose of this study was to evaluate safety and efficacy of Procarbazine (PCB) and fotemustine (FTM) combination in the treatment of pre-temozolomide treated, recurrent GBM patients. The primary end-point was progression free survival at 6 months (PFS-6). Secondary end-points were overall survival, response rates (CR + PR) and toxicity. About 54 patients (41 men and 13 women) aged 26-68 years (median age, 53.5 years) with recurrent GBM were treated. PCB was administered as an oral dosage of 450 mg on days 1-2 and a total dose of 300 mg on day 3. FTM was administered on day 3, 3 h after the last PCB intake at a dose of 110 mg/mq/BSA. The treatment was repeated every 5 weeks. Treatment was continued for a maximum of six cycles or until disease progression. After two cycles of chemotherapy: 6 patients (11.2%) experienced a neuroradiographic partial response (PR), 29 patients (53.7%) had stable disease (SD), and 19 patients (35.1%) had progressive disease (PD). For the whole group of patients, the median PFS was 19.3 weeks (95% CI, 14.1-24.4 weeks), and PFS-6 was 26.7% (95% CI, 10.6-42.8%). Overall MST from the beginning of PCB + FTM chemotherapy was 28.7 weeks (95% CI, 24.8-32.7 weeks). At 6 and 12 months, 64.4% (95% CI, 51.5-77.3%) and 23.6% (95% CI, 10.1-37.1%) of patients were alive. The median survival time calculated from the first diagnosis was 20.8 months (95% CI, 16.7-24.8). We concluded that the PCB + FTM combination as done in the current trial for patients with recurrent GBM after treatment with TMZ showed some benefit with regards to increased survival and that a Phase III trial is warranted.

Methotrexate based chemotherapy and deferred radiotherapy for primary central nervous system lymphoma (PCNSL): single institution experience

In the following study, we present our experience in the treatment of PCNSL patients using a multi-step schedule combining chemotherapy and deferred radiotherapy. Patients were treated with two modified M-BACOD cycles and then differently according to radiological response For PR, SD and PD patients, chemotherapy was interrupted and radiotherapy initiated immediately (45 Gy Whole-brain RT). With CR patients, chemotherapy was continued with a combination of HMTX, VCZ, PCB and HD Ara-C up to a total of nine cycles. In 36 patients suitable for evaluation (2 patients had undergone tumour resection): 69.4% (25 of 36) had a complete response (CR), 19.4% (7 of 36) had a partial response(PR), 8.3% (3 of 36) had stable disease(SD), and 2.7% (one of 36) had progressive disease (PD). The PR, SD and PD patients were immediately treated by radiotherapy. In this cohort of patients, we observed 6 CR, 4 PR and 2 PD, respectively, following radiotherapy. At first relapse, a total of 16 CR patients were treated by radiotherapy for a total dose of 45 Gy. The OS was 42.1 months for the entire group of patients. In CR patients treated at the moment of recurrence by salvage radiotherapy, the TTP (time lasting from histological diagnosis until recurrence of disease before RT) was 28.3 months, with a 43.4% of disease free patients observed at 2 years. The median disease-free time observed after complete response to radiotherapy was 10.5 months. In 16 patients (34%), further progression of disease was observed following radiotherapy. Two patients developed extra-CNS disease in the breast and testis. When taking into account the patients with radiotherapy delayed at recurrence, the OS was 48 months and the survival rates were 70% and 60% at 2 years and 5 years, respectively.

Meningitis following relapsing painful ophthalmoplegia in aspergillus sphenoidal sinusitis: a case report

We report the case of a 58-year-old woman in whom relapsing painful ophthalmoplegia related to a mycetoma of the sphenoid sinus gave origin to meningitis with markedly depressed glucose levels in the cerebrospinal fluid. Surgical exeresis of the mycetoma allowed aetiological diagnosis (aspergillosis) and--together with antimycotic therapy--led to durable clinical response.

Systemic temozolomide combined with loco-regional mitoxantrone in treating recurrent glioblastoma

Twenty-two recurrent GBM patients were enrolled for second tumor debulking with local positioning of a Rickam reservoir, in order to locally deliver chemotherapy with the aim of controlling local tumor recurrence. We designed a protocol using systemic temozolomide (150 mg/sqm days 1-5 every 28) in association with mitoxantrone, delivered through the reservoir (4 mg/day 1-5 every 28) positioned into the area of tumor exeresis. After re-operation a residual tumor mass no larger than 2 cm was identified in 18/22 patients. The patients were treated with monthly cycles of chemotherapy until evolution of the tumor, but in no case for more than 10 cycles. Responses were evaluated by MRI scans performed every 2 months and images assessed according to MacDonald's criteria. Response rate: no complete responses (CR), 5 partial responses (PR), 13 stable disease (SD) and 4 progressive disease (PD) occurred. The median progression-free survival (PFS) and survival time (ST) of the whole group of treated patients was 7 and 11 months, respectively and more than a quarter of the patients survived over 18 months. During the study, the patients' compliance was complete and no dropouts occurred. Hematological toxicity was mild and after repeated local injections only minor neurological side-effects occurred. Despite some bias in patients' selection not excluded in this pilot study, results are interesting: the PFS was as long as the survival of recurrent GBM reported in the literature.