Rthp-24. pseudoprogression after proton vs. photon therapy in patients with oligodendroglioma

Proton therapy is increasingly used for treatment of primary brain tumors. Recent concern has emerged regarding potentially higher rates of pseudoprogression, the development of new enhancement within the radiation field, after proton therapy compared to photon therapy. Pseudoprogression can be difficult to distinguish from true progression and is poorly described for patients with oligodendroglioma. We retrospectively reviewed 68 patients with grade 2 or 3 oligodendroglioma treated with proton (n = 27) or photon (n = 41) therapy. All patients were treated between 2004 and 2015 and had a minimum of 6 months of radiographic follow up. Median radiographic follow-up after radiation was 35 months in the photon group and 22 months in the proton group. Pseudoprogression developed in 5/41 photon-treated patients (12%) and 5/27 proton-treated patients (19%) (p = 0.5). Of 41 patients treated with more than 54 Gy, 7 developed pseudoprogression (17%) vs. 3 of 27 patients treated with 54 Gy or less (11%; p = 0.7). Of 23 patients with grade 2 oligodendroglioma, 3 developed pseudoprogression (13%) vs. 7 of 45 (16%) patients with grade 3 oligodendroglioma (p = 1.0). 1p19q status was available for 56 patients; 6/44 (14%) of patients with 1p19q codeletion developed pseudoprogression vs. 1/12 (8%) of patients without 1p19q codeletion (p = 1.0). These findings suggest that there is no difference in rates of pseudoprogres...
Source: Neuro-Oncology - Category: Cancer & Oncology Authors: Tags: RADIATION THERAPY Source Type: research