“Summary
Radiotherapy—despite being a local therapy that meanwhile is characterized by an impressively high degree of spatial accuracy—can stimulate systemic phenomena which occasionally lead to regression and rejection of non‐irradiated, distant tumor lesions. These abscopal effects of local irradiation have been observed in sporadic clinical case reports since the beginning of the 20th century, and extensive preclinical work has contributed to identify systemic anti‐tumor immune responses as the underlying driving forces. Although abscopal tumor regression still remains a rare event in the radiotherapeutic routine, increasing numbers of cases are being reported, particularly since the clinical implementation of immune checkpoint inhibiting agents. Accordingly, interests to systematically exploit the therapeutic potential of radiotherapy‐stimulated systemic responses are constantly growing. The present review briefly delineates the history of radiotherapy‐induced abscopal effects and the activation of systemic anti‐tumor immune responses by local irradiation. We discuss preclinical and clinical reports with specific focus on the corresponding controversies, and we propose issues that should be addressed in the future in order to narrow the gap between preclinical knowledge and clinical experiences.”
https://onlinelibrary.wiley.com/doi/ful ... /imr.12573
Abscopal, immunological effects of radiotherapy: Narrowing the gap between clinical and preclinical experiences
Re: Abscopal, immunological effects of radiotherapy: Narrowing the gap between clinical and preclinical experiences
9 CASE REPORTS
Over the last decades, several case reports of RT‐induced abscopal effects have been published. A systematic search of the respective literature reveals that sometimes the definition of abscopal effects is not restricted to out‐of‐field responses toward RT only but also to other types of therapy,138 whereas in other cases abscopal effects stimulated by RT are described as ‘spontaneous tumor regression’, thus rendering comprehensive analyses challenging.139-141 At first sight, the majority of patients with RT‐induced abscopal effects are of advanced age, suffer from progressed and metastasized cancer, and are treated in palliative settings (Table 2). Although various cancer entities can be found, some occur more frequently than others, particularly malignant melanoma, lymphoma, renal cell carcinoma (RCC), and hepatocellular carcinoma (HCC). Regarding prior therapies and preexisting conditions, the group of patients is highly heterogeneous.139, 142-145 Some patients have undergone multiple different treatment approaches,146, 147 and in other cases new additional therapies were started directly after the abscopal effects had been noticed.144, 145 Follow‐up times are commonly short, and causes of death are often not documented in detail.148, 149 Most of the available case reports seem to reliably present RT‐induced abscopal effects. Nevertheless, especially with such unusual and rare phenomena, a careful, well‐structured and complete presentation is of primary importance. Moreover, systematic analysis of the available reports is complicated by very heterogeneous depth in information, incoherent assessment criteria, missing time specifications and statistics, as well as hardly any patient and treatment details.145 Importantly, the question about consistent documentation arises, as publications mostly are restricted to university hospitals, thus implying a bias for statistical analyses. This bias could even be aggravated by inhomogeneous availability of highly specialized imaging techniques as well as by their continuous technical improvement over time—in other words, lesions and their dynamics which might be imaged easily today would not have been detected a few decades ago.
Table 2. Selected clinical case reports of RT‐induced abscopal effects
Over the last decades, several case reports of RT‐induced abscopal effects have been published. A systematic search of the respective literature reveals that sometimes the definition of abscopal effects is not restricted to out‐of‐field responses toward RT only but also to other types of therapy,138 whereas in other cases abscopal effects stimulated by RT are described as ‘spontaneous tumor regression’, thus rendering comprehensive analyses challenging.139-141 At first sight, the majority of patients with RT‐induced abscopal effects are of advanced age, suffer from progressed and metastasized cancer, and are treated in palliative settings (Table 2). Although various cancer entities can be found, some occur more frequently than others, particularly malignant melanoma, lymphoma, renal cell carcinoma (RCC), and hepatocellular carcinoma (HCC). Regarding prior therapies and preexisting conditions, the group of patients is highly heterogeneous.139, 142-145 Some patients have undergone multiple different treatment approaches,146, 147 and in other cases new additional therapies were started directly after the abscopal effects had been noticed.144, 145 Follow‐up times are commonly short, and causes of death are often not documented in detail.148, 149 Most of the available case reports seem to reliably present RT‐induced abscopal effects. Nevertheless, especially with such unusual and rare phenomena, a careful, well‐structured and complete presentation is of primary importance. Moreover, systematic analysis of the available reports is complicated by very heterogeneous depth in information, incoherent assessment criteria, missing time specifications and statistics, as well as hardly any patient and treatment details.145 Importantly, the question about consistent documentation arises, as publications mostly are restricted to university hospitals, thus implying a bias for statistical analyses. This bias could even be aggravated by inhomogeneous availability of highly specialized imaging techniques as well as by their continuous technical improvement over time—in other words, lesions and their dynamics which might be imaged easily today would not have been detected a few decades ago.
Table 2. Selected clinical case reports of RT‐induced abscopal effects
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