Optimizing Nivolumab Efficacy: The Role of Dosing Time in Advanced Non-Small Cell Lung Cancer

Introductıon

The recent emergence of immunotherapy is a major advancement in improving outcomes for patients with advanced or metastatic non-small-cell lung cancer (NSCLC) [1,2]. Clinical trials, such as CheckMate 017 and 057, have demonstrated the superior efficacy of nivolumab compared to docetaxel in patients who experienced disease progression following initial chemotherapy [3,4]. Consequently, nivolumab was the first immune checkpoint inhibitor approved as the standard of care for patients with metastatic or advanced NSCLC who progressed during or after platinum-based chemotherapy [5,6].

The programmed cell death-1 (PD-1) receptor, expressed on activated T cells, interacts with programmed cell death ligands 1 and 2 (PD-L1 and PD-L2), which are commonly expressed on tumor cells and infiltrating immune cells in NSCLC [7,8]. This interaction suppresses T-cell activation, enabling tumor immune evasion [9]. Nivolumab, a fully human IgG4 monoclonal antibody targeting PD-1, restores antitumor immune responses by blocking this inhibitory pathway [7]. Despite these therapeutic advances, long-term remission is achieved only in a subset of patients, with response rates remaining below 20% [3,4]. Thus, identifying strategies to enhance the efficacy of nivolumab is of critical importance in clinical practice.

Recent evidence indicates that circadian rhythms – endogenous 24-hour cycles regulating numerous physiological processes – also influence immune function [10,11]. For example, CD8+ T lymphocytes, key effector cells in nivolumab therapy, demonstrate circadian variations in activity [12]. Experimental and clinical studies have reported rhythmic patterns in immune processes such as lymphocyte trafficking, antigen recognition, and cytokine secretion [13]. Moreover, chronotherapy trials in oncology suggest that drug tolerability and efficacy may depend on the timing of administration [14]. A few preliminary studies in NSCLC and other malignancies have hinted that the timing of immune checkpoint inhibitor administration could affect both clinical outcomes and immune-related toxicity [15,16]. However, findings remain inconsistent, and no consensus has been reached regarding the optimal daily time for nivolumab administration.

This knowledge gap, specifically the unresolved impact of circadian immune modulation on the efficacy of nivolumab, forms the rationale for our study. Optimizing administration timing could provide a simple and practical strategy to increase response rates without additional toxicity or cost.

The aim of our study was to evaluate whether the timing of nivolumab administration, before or after 1 PM, impacts treatment response and immune-related adverse events in patients with advanced NSCLC.

Materıal and Methods

STUDY DESIGN AND PARTICIPANTS:

This retrospective study enrolled 54 patients with advanced NSCLC who received nivolumab treatment at 2 tertiary healthcare facilities between January 2021 and January 2025. Patient data were collected retrospectively from electronic medical records, institutional oncology databases, and radiology archives. Potential biases related to retrospective data collection were minimized by using predefined inclusion and exclusion criteria and by independent verification of records by 2 investigators.

The sample size was calculated using G*Power. Parameters were set to a 5% type I error rate, 95% power, and a medium effect size (Cohen’s d=0.50) for the independent-sample t test, corresponding to a clinically meaningful difference anticipated between treatment timing groups. This resulted in a minimum total sample of 45 participants. The final cohort included 54 patients who met the eligibility criteria.

All patients had stage IV NSCLC and had progressed following platinum-based doublet chemotherapy (eg, paclitaxel, docetaxel, or gemcitabine combined with carboplatin or cisplatin). Radiotherapy to the lung was permitted. Nivolumab was administered intravenously at 3 mg/kg every 14 days.

INCLUSION AND EXCLUSION CRITERIA:

Eligible patients were: (1) ≥18 years old; (2) receiving regular follow-up at participating centers; (3) undergoing baseline PET-CT prior to nivolumab initiation; (4) completing at least 1 follow-up PET-CT during nivolumab therapy; and (5) having immune-related adverse events (irAEs) documented in standardized forms every 14 days. Exclusion criteria were: (1) symptomatic brain metastases; (2) activating EGFR, ALK, or ROS1 alterations; (3) uncontrolled autoimmune disease; (4) multiple prior systemic therapy lines; and (5) inconsistency in treatment administration times. Patients with recorded treatment times that varied across morning and afternoon sessions were excluded.

TREATMENT ADMINISTRATION TIME:

Patients were stratified into 2 groups according to nivolumab administration time: before 1: 00 PM or after 1: 00 PM. The 1: 00 PM cutoff was chosen based on prior reports using similar midday thresholds (12: 06 PM and 12: 54 PM in previous studies [15,16]), in combination with our clinic workflow patterns. This cutoff enabled consistent stratification while ensuring comparability with prior research.

PATHOLOGICAL AND RADIOLOGICAL ASSESSMENT:

Pathological diagnosis of NSCLC was confirmed by institutional pathology departments. PD-L1 expression was not used as an inclusion criterion. Patients were included only if genomic testing confirmed EGFR, ALK, and ROS1 wild-type status.

Treatment response was assessed radiologically using PET-CT according to PET Response Criteria in Solid Tumors (PERCIST 1.0). Three independent nuclear medicine specialists, blinded to administration time, classified responses as complete response, partial response, stable disease, or progressive disease. Inter-observer discrepancies were resolved by consensus discussion, ensuring consistency and objectivity.

SIDE EFFECT ASSESSMENT:

Immune-related adverse events were assessed at every visit using standardized forms and graded according to the Common Terminology Criteria for Adverse Events (CTCAE v5.0).

STATISTICAL ANALYSIS:

Statistical analyses were conducted with IBM SPSS Statistics for Windows, Version 25.0. Descriptive statistics were provided, with categorical variables presented as frequencies and percentages. Between-group comparisons of categorical variables were performed using chi-square or Fisher’s exact tests as appropriate. Continuous variables (eg, age) were summarized as mean±standard deviation or median (interquartile range), depending on distribution, and compared using independent-sample t tests or Mann-Whitney U tests. Missing data were assumed to be missing at random and handled by listwise deletion. Sensitivity analyses confirmed no impact on primary outcomes.

Progression-free survival (PFS) was estimated using the Kaplan-Meier method, and between-group differences were assessed by the log-rank (Mantel-Cox) test. As PFS did not exhibit normal distribution, it was reported as median survival. Cox regression analysis was not conducted because the study was specifically designed to test the effect of administration timing as a single stratification factor; however, we acknowledge that future studies with larger sample sizes should include multivariable Cox regression models to adjust for potential confounders such as ECOG performance status, PD-L1 expression, and comorbidities. Statistical significance was set at two-sided P<0.05.

Results

PATIENT CHARACTERISTICS:

A total of 54 patients were included, of whom 30 received nivolumab before 1 PM and 24 after 1 PM. Baseline clinical and sociodemographic characteristics are presented in Table 1.

TREATMENT RESPONSE:

Treatment responses were categorized according to PET Response Criteria in Solid Tumors (PERCIST 1.0). In the before 1 PM group, 12 patients (40%) had progressive disease, 5 (16.7%) had stable disease, 7 (23.3%) achieved partial response, and 6 (20%) achieved complete response. In contrast, in the after 1 PM group, 17 patients (70.8%) had progressive disease, 2 (8.3%) had stable disease, 4 (16.7%) achieved partial response, and 1 (4.2%) achieved complete response. The difference in treatment response distribution between groups was statistically significant (P=0.025), supporting the hypothesis that earlier administration of nivolumab is associated with more favorable clinical outcomes (Table 2).

PROGRESSION-FREE SURVIVAL:

Median progression-free survival (PFS) was 3.5 months for patients treated before 1 PM and 3.2 months for those treated after 1 PM. Although numerically longer in the early treatment group, the difference was not statistically significant (P=0.098) (Table 3, Figure 1).

IMMUNE-RELATED ADVERSE EVENTS:

Immune-related adverse events occurred in 10 patients overall. These were observed in 4 patients (13.3%) treated before 1 PM and in 6 patients (25.0%) treated after 1 PM. While events were more frequent in the later treatment group, the difference was not statistically significant (p=0.273). All adverse events were grade 1–2, and no grade ≥3 toxicities were observed (Table 4).

Discussion

LIMITATIONS:

The study has several limitations that directly impact interpretation of the results. The retrospective design introduced inherent biases, and the modest sample size reduced the statistical power. The choice of 1 PM as the cutoff, while informed by prior chronotherapy studies [15,16], lacks a definitive biological rationale. This limits the strength of our conclusions and highlights the need for prospective studies that systematically examine multiple time points to determine optimal administration schedules. Additionally, important biological correlates, such as circadian fluctuations in PD-1/PD-L1 expression, T-cell activity, and cytokine secretion, were not assessed, representing a major mechanistic gap. Finally, overall survival, the most clinically meaningful endpoint, was not yet available due to ongoing follow-up.

NOVEL CONTRIBUTIONS AND IMPLICATIONS:

Despite these limitations, this study contributes novel evidence to the field of cancer chronotherapy by demonstrating that the timing of nivolumab administration may affect treatment response in NSCLC. Our results underscore the need for further investigation of circadian influences on immunotherapy, both in mechanistic studies and in larger, prospective clinical trials. If confirmed, timing-based strategies could provide a simple, cost-neutral method to enhance treatment efficacy and inform personalized immunotherapy schedules.

Conclusions

PD-1/PD-L1 inhibitors have transformed the treatment of advanced NSCLC, yet response rates remain limited despite proven overall survival benefits [3,4]. In this retrospective study, we observed that nivolumab administration before 1 PM was associated with significantly better treatment response rates compared to later administration, while PFS showed only a non-significant numerical advantage. These findings suggest that circadian timing can influence the efficacy of immune checkpoint inhibition.

Given the retrospective design, modest sample size, and absence of overall survival data, our results should be interpreted with caution. Nevertheless, they contribute to the emerging field of cancer chronotherapy, highlighting circadian rhythms as a potential determinant of immunotherapy outcomes.

The key takeaway is that treatment timing may be a simple, cost-neutral strategy to improve patient outcomes. Future prospective studies with larger cohorts and mechanistic biomarker assessments are needed to validate these observations, identify the optimal administration window, and clarify the underlying biological mechanisms. If confirmed, such insights could inform the design of chronotherapy-based clinical trials and the development of personalized treatment schedules in immuno-oncology.