Abstract
Photodynamic therapy (PDT) subsequent to surgical tumor removal is a novel localized treatment for malignant glioma that provides effective local control. The acute response of malignant glioma to PDT can be detected as linear transient hyperintense signal on diffusion-weighted imaging (DWI) and a decline in apparent diffusion coefficient values without symptoms. However, their long-term clinical significance has not yet been examined. The aim of this study was to clarify the link between hyperintense signal on DWI as an acute response and recurrence after PDT in malignant glioma. Thirty patients (16 men; median age, 60.5 years) underwent PDT for malignant glioma at our institution between 2017 and 2020. We analyzed the signal changes on DWI after PDT and the relationship between these findings and the recurrence pattern. All patients showed linear hyperintense signal on DWI at the surface of the resected cavity from day 1 after PDT. These changes disappeared in about 30 days without any neurological deterioration. During a mean post-PDT follow-up of 14.3 months, 19 patients (63%) exhibited recurrence: 10 local, 1 distant, and 8 disseminated. All of the local recurrences arose from areas that did not show hyperintense signal on DWI obtained on day 1 after PDT. The local recurrence in malignant glioma after PDT occurs in an area without hyperintense signal on DWI as an acute response to PDT. This characteristic finding could aid in the monitoring of local recurrence after PDT.
Highlights
Survival is associated with the extent of resection in patients with glioblastoma, the most aggressive primary malignant brain tumor [1,2,3,4]
All of the local recurrences arose from areas that did not show hyperintense signal on diffusion-weighted imaging (DWI) obtained on day 1 after Photodynamic therapy (PDT)
We previously reported that the acute response of malignant glioma to PDT can be detected as transient linear hyperintense signal on diffusion-weighted imaging (DWI) and a decline in apparent diffusion coefficient (ADC) values without symptoms [23]
Summary
Survival is associated with the extent of resection in patients with glioblastoma, the most aggressive primary malignant brain tumor [1,2,3,4]. Standard therapy includes maximal possible surgical resection followed by radiotherapy and concomitant temozolomide-based chemotherapy and often leads to local recurrence [6,7,8,9,10]. Photodynamic therapy (PDT) subsequent to surgical tumor removal is a novel localized treatment for malignant glioma and a possible alternative to standard therapy. PDT is a light-activated treatment modality that provides effective local control [11,12,13]. Even PDT cannot completely suppress local recurrence [11, 12]
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