This study is the first to examine sleep patterns in cancer patients receiving ICI therapy. Our study also assessed objective sleep patterns over time in cancer patients post ICI treatment initiation, which, to our knowledge, has not been done before. We found a high burden of sleep problems in this ICI cohort. In particular, two-thirds of enrolled participants had intermediate to high sleep apnea risk and an average / restless night sleep, more than half experienced clinically significant insomnia, and about a third reported taking longer than 15 min to fall asleep and evening chronotype. We also observed that objective sleep patterns remained mostly consistent over time in a subset of participants assessed, suggesting that sleep information collected at study baseline remains indicative of sleep patterns through, at least, early stages of the treatment period. In a multivariable-adjusted regression analysis, we did not find a statistically significant association between intermediate or high risk OSA and metastatic cancer compared to low risk OSA. However, of the secondary sleep problems assessed, patients who reported taking longer to fall asleep were more likely to have been diagnosed with metastatic cancer compared to those reporting shorter sleep latency. Additionally, patients reporting an evening chronotype (patients who are most active and alert in the evening) were more likely to have been diagnosed with metastatic cancer compared to those reporting a morning chronotype (patients who are most active and alert in the morning). Our second goal was to determine the association between sleep problems and ICI treatment tolerance. While we did not find any significant association between OSA risk, insomnia, and six or more infusions during the first six months after ICI initiation, the direction of the estimates showed higher odds for poor ICI treatment tolerance in patients with certain sleep problems.
Our study corroborates other studies of sleep problems in more traditional cancer treatment cohorts (e.g., patients receiving radiotherapy and chemotherapy).18,19 In particular, prior studies noted a high burden of sleep problems, including insufficient sleep duration, insomnia symptoms, and poor overall sleep quality,18,19 that have been, in turn, linked with poor cancer prognosis.1,28 For instance, cancer patients with insufficient sleep duration (≤ 6 h sleep/night) and who snore might be experiencing more severe underlying sleep problems and, therefore, subsequent worse cancer outcomes.1,28 Additionally, the longitudinal sleep data collected with the sleep score max may suggest the impact of the single time point sleep are durable over time.
The results from these analyses have some key limitations. Chief amongst them is the limited sample size, which could explain the mostly non-statistically significant results. Relatedly, although we limited our study to patients receiving ICI within two clinical units at a single institution, the physiologic insults of sleep problems on cancer prognosis are heterogeneous across cancer sites and possibly molecular types.17,29,30 Thus, by combining data across patients with multiple cancer sites, some cancer site-specific relationships may have been obscured. However, small numbers precluded us from conducting site-specific analyses.
Secondly, study participants self-reported their sleep problems. Given the focus of this study on the patient population initiating ICI for the treatment of their late-stage cancer, several factors might be impacting participant sleep patterns (e.g., stress, side effects from previous lines of therapy as illustrated in Fig. 1); thus, observed sleep patterns may not be reflective of pre-diagnostic sleep patterns. In addition, it is possible that poor cancer prognosis could cause sleep problems instead of the reverse (Fig. 1). However, this is less concerning for the ICI response outcome analysis since it is downstream of reported sleep problems at enrollment. Additionally, our study did not measure immune response biomarkers (e.g., inflammatory markers cytokines, including IL-1, IL-6, and TNF-α) that may be more sensitive to underlying sleep problems.31,32 However, our sleep data is based on validated questionnaires and, unlike most studies assessing sleep problems in cancer which have focused on a single sleep dimension (e.g., sleep duration)33, we evaluated multiple sleep dimensions, including STOP-BANG OSA risk levels.23,34
Another important study limitation is in the assessment of ICI response. The primary response measure in ICI studies and the clinic settings is based on RECIST 1.1 guidelines.35 The guideline is based on tumor imaging data incorporating information on changes in lesion size and new lesions to distinguish ICI "responders" from "non-responders".35 We were unable to incorporate the guidelines into our study due to lack of this data at the end of 6 months follow-up.
Finally, there is also an issue of representativeness of the SCCA cancer population to the general ICI cancer treatment population. Specifically, our study population is racially homogenous (mainly of European descent, 85% white) and likely have higher socio-economic status.
Despite these study limitations, this study is the first, to our knowledge, to examine the biologically plausible and potential impact of sleep problems in cancer patients receiving ICI therapy. In result, given the burden and potential impact of sleep problems on ICI treatment response, we believe the study limitations are outweighed by the importance of this study in setting the stage for larger studies with more comprehensive sleep and ICI response assessments.