Background:Pseudoprogression is known to occur after immune-checkpoint inhibitor (ICI) therapy in brain metastasis and can complicate clinical decision-making. Still, its incidence, timing, and clinical presentation remain unclear. A retrospective cohort study in melanoma and non-small cell lung cancer brain metastasis patients was conducted to address this.Materials and Methods:Brain metastasis patients showing progression on MRI according to response assessment in neuro-oncology brain metastases criteria after starting ICI therapy were included, irrespective of prior irradiation. Lesions were classified as tumour progression (TP) or pseudoprogression based on three-month radiological follow-up or histopathology. TP was assigned if progression was again shown at three months. Pseudoprogression was assigned if lesions showed stability, partial, or complete response at three months. ‘Non-classified’ lesions were those with new or changed treatment during follow-up.Results:A cohort of 98 patients with 233 lesions was included over a 13-year period; 170 lesions were considered non-classified, and 41 and 22 lesions were classified as TP and pseudoprogression respectively. This resulted in a lesion- and patient-specific incidence for pseudoprogression of 9.4% and 17.3% respectively. Due to the large number of lesions that could not be classified, as is the case in clinical practice, the reported incidence in this study is likely an underestimation and can be seen as a ‘minimum’ incidence rate. Ten pseudoprogression (45.5%) and 13 (31.7%) TP lesions were previously irradiated. Pseudoprogression occurred at a median of 2.7 months after starting ICI therapy. The only clinical feature distinguishing patients with TP from pseudoprogression was that TP patients were more likely to need dexamethasone for neurological symptoms.Conclusions:Pseudoprogression has a lesion-specific incidence rate of at least 9.4% and occurs at a median of 2.7 months after starting ICI therapy. Severe neurological symptoms requiring dexamethasone may be a clinical feature typical for TP.
背景：已知免疫检查点抑制剂（ICI）治疗后脑转移病灶可能出现假性进展，这可能使临床决策复杂化。然而，其发生率、发生时间及临床表现仍不明确。为此，我们针对黑色素瘤和非小细胞肺癌脑转移患者开展了一项回顾性队列研究。 材料与方法：研究纳入在开始ICI治疗后，根据神经肿瘤脑转移疗效评估标准显示MRI进展的脑转移患者，无论既往是否接受过放疗。根据三个月影像学随访或组织病理学结果，将病灶分为肿瘤进展（TP）或假性进展。若三个月时再次显示进展则判定为TP；若病灶在三个月时显示稳定、部分缓解或完全缓解则判定为假性进展。"未分类"病灶指随访期间接受新治疗或变更治疗的病灶。 结果：在13年期间共纳入98例患者的233个病灶；其中170个病灶被视为未分类，41个和22个病灶分别被归类为TP和假性进展。由此得出病灶特异性和患者特异性的假性进展发生率分别为9.4%和17.3%。由于大量病灶无法分类（临床实践中常见此情况），本研究报告的发生率很可能被低估，可视为"最低"发生率。既往接受过放疗的病灶中，假性进展占10个（45.5%），TP占13个（31.7%）。假性进展发生的中位时间为开始ICI治疗后2.7个月。区分TP与假性进展患者的唯一临床特征是：TP患者更可能因神经系统症状需要使用地塞米松。 结论：假性进展的病灶特异性发生率至少为9.4%，中位发生时间为开始ICI治疗后2.7个月。需要地塞米松治疗的严重神经系统症状可能是TP的典型临床特征。
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