BACKGROUND. Radiotherapy (RT) plus concomitant and adjuvant temozolomide (TMZ) is now the standard of care for patients with newly diagnosed glioblastoma. The occurrence of pseudo-progression directly after RT is a recognized phenomenon, but to the authors' knowledge its incidence after combined RT/TMZ is unknown. The occurrence of early pseudo-progression was retrospectively assessed in a cohort of malignant glioma patients treated with RT/TMZ. METHODS. The pre-RT and post-RT brain scans from patients treated with RT/TMZ for a malignant glioma were reviewed. Scans were made before the start of RT, 4 weeks after the end of RT, and every 3 months thereafter. In addition, information was collected regarding clinical signs and symptoms, dexamethasone dose, histology, and survival. RESULTS. Eighty-five patients were identified. In 36 patients (42%) the first followup scan 4 weeks after the end of RT indicated disease progression. Of these 36 patients, 18 (50%) were diagnosed with pseudo-progression. None of the patients received additional treatment other than TMZ. Six of 18 patients with pseudo-progression and 12 of the 18 patients with real tumor progression developed new clinical signs and symptoms during RT or in the first 4 weeks thereafter. CONCLUSIONS. Up to 50% of malignant glioma patients treated with RT/TMZ and progression immediately after RT develop pseudo-progression. The current study data support the idea to continue TMZ in the case of progressive lesions immediately after RT/TMZ. Surgery should be considered in symptomatic cases. The inclusion of patients with progressive lesions developing direcdy after chemoradiation in studies regarding recurrent gliomas will lead to an overestimation of the results.

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Erasmus MC: University Medical Center Rotterdam

Taal, W, Brandsma, D, de Bruin, H.G, Bromberg, J.E.C, Swaak-Kragten, A.T, Smitt, P.A, … van den Bent, M.J. (2008). Incidence of early pseudo-progression in a cohort of malignant glioma patients treated with chemoirradiation with temozolomide. Cancer, 113(2), 405–410. doi:10.1002/cncr.23562