Our study recommends that it is feasible to complete a comprehensive assessment of cognitive outcomes in 30 patients with newly diagnosed aggressive lymphoma over the course of treatment and recovery.
Despite the distressing, challenging and stressful nature of the lymphoma diagnosis, recruitment to our study exceeded our expectations, with 30 patients with newly diagnosed aggressive lymphoma recruited over a 10-month period, and only three people declining participation. Participants may have been motivated to take part to help others. Results describing motivation and reasons for sustained participation have been published previously. 
Patients willing to participate in the study were often consented within days of diagnosis. Thirteen (43%) were consented on day of being informed of diagnosis. Consent was obtained in a variety of clinical settings, with seven (23%) participants being inpatients, five in the dedicated haematology ward, and two in general surgical wards. The median time between being informed of diagnosis and pre-chemotherapy NPA assessment was 7 days (range 0 to 49), with 4 (13%) participants informed of diagnosis, consented to the study and assessed on the same day. The environment for collection of neuropsychological data was flexible and included a variety of clinical settings (e.g., day oncology unit, outpatient clinic, or inpatient unit). Management of potential disruption by clinical staff in the inpatient setting was minimised by placing a ‘do not disturb’ sign on door. The median time between being informed of diagnosis and date of treatment commencement was 12 days (range 0 to 99); with one (3%) participant being informed of diagnoses, consented, assessed and commencing treatment on the same day.
Retention and compliance with all measures was excellent, despite literature reporting challenges with recruitment of patients who have recently been diagnosed with cancer.  Other studies have reported that retention of participants to longitudinal studies can be challenging, [36–38] and attrition is often attributed to poor study design. [38, 39] A recent study by Janelsins et al. (2021) assessed longitudinal changes in cognition in patients with lymphoma before and after chemotherapy; however, they did not include a mid-treatment assessment. They experienced significant attrition throughout the study; retention immediately post-chemotherapy was 86%, and 72% 6 months post-chemotherapy, with losses to follow-up being the main reason for attrition.  This may have been multifactorial and exacerbated by there being no mid-treatment assessment, potentially causing lack of interest or motivation for participants to stay engaged.
Success with recruitment and compliance with assessments in the current study was likely due to flexibility in testing time and location, reflecting the availability of the study nurse across all clinical settings. In particular, this flexibility enabled study assessments to take place at times convenient to the participants, usually when they were already at the hospital, thereby reducing any additional travel demands. Importantly, participants were approached at the hospital by the study nurse, possibly contributing to the high recruitment rate. The study nurse may have been seen as a trustworthy credible member of the team.  While not involved in clinical care at the time of diagnosis, the study nurse responsible for recruiting patients and conducting assessments was an experienced haematology nurse and a clinician nurse-researcher.  As such she was in a privileged position, being a long-standing staff member in the clinical setting, which may have strengthened the clinical team’s motivation to identify and refer patients to the study.  Additionally, potential participants likely appreciated the study nurse’s clinical expertise, and this may have improved trust among patients, encouraging participation. [38–40] These observations highlight the potential benefit of clinician involvement in data collection,  strengthening capacity for clinical research, notwithstanding the related ethical concerns of the study nurse-participants relationship grounded in trust but open to participant coercion.
Interview studies were conducted to examine the acceptability of the study protocol. Initially, a participant burden interview was undertaken with the first five participants, where no changes to the assessment schedule were recommended by any participant.  Feasibility of the study was later confirmed via a separate qualitative sub-study that explored the motivations for initial and ongoing participation at a time of heightened stress related to a new diagnosis of aggressive lymphoma and the rapid commencement of treatment. Ease of participation; personal values that impact attitude to participation; desire to engage in self-help; and appreciation of additional support motivated ongoing participation. 
Despite all eligible participants agreeing to participate in the neuroimaging sub-study, only 11 of 30 (37%) were deemed eligible as diagnostic PET/CT scans had been acquired prior to attending the lymphoma service for the other patients. Our results speak to the difficulty of capturing baseline neuroimaging assessments in all patients, however, in those who were eligible for the sub-study it was feasible. We found challenges with collecting longitudinal research quality PET/CT brain acquisition studies, which require constraints on scan time acquisition and camera availability, to assess any biomarker change over time, was difficult to implement in a clinical setting. Notwithstanding excellent compliance among those who were eligible, some participants found the brain scans to be challenging, arduous and time-consuming, and thus these data should only be collected in future studies if critical, given reports of participant burden.
This study has limitations that impact the generalisability of results. The sample size was small, and participants were all recruited from a single institution. Furthermore, despite the high proportion of patients consenting to participate and the involvement of a haematology nurse specialist may limit replicability in other centres. There were several challenges identified in the neuroimaging sub-study which were detailed in the results section. We recommend strong collaboration with the PET imaging centre, and longer imaging slots for each participant. However, this may increase costs associated with imaging and potentially place more demands on participants, who are already under considerable stress. Future studies should aim to recruit a larger patient cohort from across multiple institutions and should include patients from different cancer groups.