Radiotherapy (RT) has traditionally been considered a local treatment modality; however, accumulating evidence suggests that it can induce systemic antitumor responses outside the irradiated field. The classical abscopal effect, defined as the regression of non-irradiated tumor lesions following localized RT, has gained renewed attention in the era of immune checkpoint inhibitors (ICIs). Preclinical and clinical studies have demonstrated that RT can promote immunogenic cell death, antigen presentation, cytokine release, and adaptive immune activation, processes that may contribute to systemic antitumor immunity, particularly when combined with ICIs. Clinically apparent abscopal responses remain rare and heterogeneous, and the biological mechanisms underlying these phenomena are not completely understood. Systemic tumor regression has occasionally been observed in clinical settings that do not involve checkpoint blockade, including RT alone, chemotherapy-containing regimens, and central nervous system-directed therapies. These findings suggest that radiation-associated systemic antitumor responses may arise through overlapping immunologic mechanisms involving both innate and adaptive immunity, tumor microenvironment remodeling, and treatment-associated cellular stress. This review summarizes the current clinical evidence and biological mechanisms underlying radiation-associated systemic antitumor responses and discusses emerging concepts extending beyond the conventional RT–immunotherapy paradigm. We further examined unresolved challenges, including treatment heterogeneity, biomarker limitations, pseudoprogression, and difficulties in mechanistic confirmation. Finally, we propose that the broader “beyond-abscopal” framework may serve as a hypothesis-generating conceptual model for investigating systemic tumor responses across diverse treatment contexts while emphasizing the need for cautious interpretation and prospective translational validation.

Treatment-associated regression of tumors outside the irradiated field has occasionally been reported, but the underlying mechanisms remain unclear, particularly in the context of central nervous system (CNS)–directed therapy. Glioblastoma (GBM) is commonly treated with radiotherapy and temozolomide, both of which may influence tumor biology and the systemic environment. We report a patient with synchronous primary GBM and early-stage lung adenocarcinoma who underwent craniotomy followed by intensity-modulated radiotherapy with concurrent temozolomide for GBM. During GBM-directed chemoradiotherapy, the untreated pulmonary lesion demonstrated progressive regression without any lung-specific therapy, temporally coinciding with CNS-targeted treatment. Although comprehensive immunophenotyping was not feasible, longitudinal changes in the proportion of peripheral blood lymphocytes were observed during therapy. These findings represent a clinical observation characterized by a temporal association between CNS-directed treatment and regression of a distant, non-irradiated tumor. However, the underlying mechanism remains uncertain, and a contribution from systemic temozolomide exposure cannot be excluded. While treatment-related systemic effects may be considered, no specific causal mechanism can be established based on this single case. This case highlights an unusual clinical observation that may warrant further investigation. Further studies are needed to clarify the relationship between CNS-directed therapies and systemic tumor behavior.

Cerebral amyloid angiopathy-related inflammation (CAA-ri) is a rare inflammatory subtype of cerebral amyloid angiopathy that may present with leptomeningeal enhancement on magnetic resonance imaging (MRI), thereby mimicking leptomeningeal metastasis (LM) in patients with cancer. We report the case of an 82-year-old woman with a recently resected lung adenocarcinoma who underwent brain MRI following a fall. MRI revealed bilateral asymmetric white matter hyperintensities and multifocal leptomeningeal enhancement, which initially suggested LM. However, preserved neurological function, negative cerebrospinal fluid cytology, and the subsequent identification of numerous cortical and subcortical microbleeds on targeted reassessment with susceptibility-weighted MRI prompted diagnostic reassessment. Brain biopsy demonstrated vascular amyloid deposition with perivascular inflammatory infiltrates, confirming CAA-ri. Because the patient remained neurologically stable, she was managed conservatively, and spontaneous radiological improvement was observed during follow-up. This case highlights the fact that leptomeningeal abnormalities in patients with lung cancer do not invariably represent leptomeningeal metastasis. When clinicoradiological findings are discordant, prompt reassessment using appropriately selected MRI sequences should be integrated with cerebrospinal fluid analysis and multidisciplinary evaluation, with pathological confirmation considered when clinically consequential alternative diagnoses cannot be excluded. This approach may help avoid inappropriate LM-directed therapy.

Cancer therapy-related acute kidney injury has become an increasingly common challenge as modern treatments prolong survival and increase exposure to potentially nephrotoxic therapies. Decisions regarding therapeutic rechallenge have relied on normalizing serum creatinine and recovering estimated glomerular filtration rate, despite growing evidence that biochemical recovery does not necessarily indicate restoration of kidney integrity or resilience. In this review, we propose biological kidney recovery as a conceptual framework that integrates mechanisms of kidney injury and repair (adaptive and maladaptive) with emerging biomarkers and therapeutic rechallenge. We first summarize the distinct mechanisms of kidney injury induced by platinum-based chemotherapy, immune checkpoint inhibitors, and vascular endothelial growth factor pathway inhibitors, highlighting how these differences influence subsequent repair. We then discuss the cellular and metabolic processes underlying adaptive repair, the transition to maladaptive remodeling, and current approaches for assessing biological recovery through pathology, biomarkers, and multi-omics technologies. Finally, we present a practical framework for individualized therapeutic rechallenge based on an integrated assessment of kidney-, tumor-, and patient-related factors and outline future directions for precision onco-nephrology. By shifting the focus from filtration alone to biological recovery, this framework enables more informed therapeutic rechallenge aimed at preserving both oncologic efficacy and long-term kidney health.