Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment by enhancing antitumor immune responses; however, clinical outcomes remain highly variable across patients and tumor types. While tumor-intrinsic factors such as PD-L1 expression and tumor mutational burden provide some predictive value, they do not fully explain response heterogeneity. Increasing evidence highlights the critical role of host-related determinants in modulating ICI efficacy. This review provides a comprehensive overview of key host factors, including baseline immune competence, T-cell repertoire diversity, cytokine profiles, and peripheral biomarkers. It further examines the impact of germline genetics, HLA genotype, and epigenetic regulation on immune responses. The role of the gut microbiome and its metabolites is explored, alongside the impact of metabolic status, obesity, nutrition, and lifestyle behaviors. Additionally, the effects of co-medications and comorbidities are discussed. Integrating these host-related factors may improve patient stratification and support the development of personalized immunotherapy strategies.

Introduction and importance: Renal artery occlusion following blunt abdominal trauma is uncommon and is rarely reported in the emergency department. It has traditionally been managed with surgical intervention, but new methods are emerging that involve conservative therapy and minimally invasive procedures, making proficiency in anatomy necessary for successful clinical management. Case presentation: This report describes a 20-year-old woman with unilateral left renal artery occlusion after a motor vehicle accident. Despite a left tibial fracture and a flank contusion, she remained hemodynamically stable. The diagnosis was confirmed with a whole-body CT scan, which showed occlusion of the inferior branch of the left renal artery and lower lobe infarction, with findings supported by diagnostic angiography. A conservative, minimally invasive treatment plan, including daily aspirin and intravenous opioids for pain, was successfully used, resulting in a good prognosis with stable kidney function and relief of pain at 1-month follow-up. Discussion: A review of the literature was also performed to summarize the best diagnostic and management tools in such cases, and the literature indicates that CT scanning is the superior diagnostic tool, with evidence supporting minimally invasive and conservative management as the best treatment plan over surgical repair or nephrectomy unless otherwise justified. Conclusion: Renal artery occlusion following blunt abdominal trauma is rare. CT angiography is crucial for timely diagnosis. Minimally invasive and conservative management offers favorable outcomes and preserves renal function.

Background/Objectives: Immune checkpoint inhibitors have revolutionized the treatment of advanced melanoma, yet primary and acquired resistance remain major barriers to durable disease control. This narrative review examines the clinical patterns, biological mechanisms, biomarker limitations, and therapeutic implications of immunotherapy failure. Methods: A structured search of PubMed, Web of Science, and ClinicalTrials.gov identified relevant studies published from January 2010 to May 2026, supplemented by landmark earlier reports. Results: Immunotherapy resistance encompasses heterogeneous patterns, including early progression, oligoprogression, dissociated response, brain-dominant progression, relapse after response, and progression after treatment discontinuation. These clinical phenotypes arise from overlapping mechanisms such as loss of antigen presentation, impaired interferon signaling, oncogenic immune exclusion, melanoma dedifferentiation, suppressive myeloid and regulatory T-cell programs, stromal and vascular barriers, metabolic restriction, and deterioration of tumor-reactive T-cell clones. Conventional response criteria and static biomarkers, including PD-L1 expression and tumor mutational burden, do not adequately capture this complexity because resistance varies across lesions and evolves under treatment pressure. Negative trials of IDO1 inhibition, cytokine intensification, vaccines, and intratumoral immune stimulation further show that biological plausibility and early activity do not guarantee clinical benefit when target engagement, patient enrichment, and endpoint selection are inadequate. Conclusions: Immunotherapy resistance in melanoma should be viewed as a variety of biologically distinct clinical states rather than a single endpoint. Future progress will require resistance-matched treatment, longitudinal tissue and circulating tumor DNA assessment, adaptive trial designs, and endpoints aligned with treatment kinetics. This framework may improve salvage selection and interpretation of post-PD-1 studies in clinical practice.