Yasuyoshi Chiba, Manabu Kinoshita, Yoshiko Okita, Akihiro Tsuboi, Kayako Isohashi, Naoki Kagawa, Yasunori Fujimoto, Yusuke Oji, Yoshihiro Oka, Eku Shimosegawa, Satoshi Morita, Jun Hatazawa, Haruo Sugiyama, Naoya Hashimoto and Toshiki Yoshimine
Immunotherapy targeting the Wilms tumor 1 (WT1) gene product is a promising treatment modality for patients with malignant gliomas, and there have been reports of encouraging results. It has become clear, however, that Gd-enhanced MR imaging does not reflect prognosis, thereby necessitating a more robust imaging evaluation system for monitoring response to WT1 immunotherapy. To meet this demand, the authors performed a voxel-wise parametric response map (PRM) analysis of 11C-methionine PET (MET-PET) in WT1 immunotherapy and compared the data with the overall survival after initiation of WT1 immunotherapy (OSWT1).
Fourteen patients with recurrent malignant glioma were included in the study, and OSWT1 was compared with: 1) volume and length change in the contrast area of the tumor on Gd-enhanced MR images; 2) change in maximum uptake of 11C-methionine; and 3) a more detailed voxel-wise PRM analysis of MET-PET pre- and post-WT1 immunotherapy.
The PRM analysis was able to identify the following 3 areas within the tumor core: 1) area with no change in 11C-methionine uptake pre- and posttreatment; 2) area with increased 11C-methionine uptake posttreatment (PRM+MET); and 3) area with decreased 11C-methionine uptake posttreatment. While the results of Gd-enhanced MR imaging volumetric and conventional MET-PET analysis did not correlate with OSWT1 (p = 0.270 for Gd-enhanced MR imaging length, p = 0.960 for Gd-enhanced MR imaging volume, and p = 0.110 for MET-PET), the percentage of PRM+MET area showed excellent correlation (p = 0.008) with OSWT1.
This study describes the limited value of Gd-enhanced MR imaging and highlights the potential of voxel-wise PRM analysis of MET-PET for monitoring treatment response in immunotherapy for malignant gliomas. Clinical trial registration no.: UMIN000002001.
Shuichi Izumoto, Akihiro Tsuboi, Yoshihiro Oka, Tsuyoshi Suzuki, Tetsuo Hashiba, Naoki Kagawa, Naoya Hashimoto, Motohiko Maruno, Olga A. Elisseeva, Toshiaki Shirakata, Manabu Kawakami, Yusuke Oji, Sumiyuki Nishida, Satoshi Ohno, Ichiro Kawase, Jun Hatazawa, Shin-ichi Nakatsuka, Katsuyuki Aozasa, Satoshi Morita, Junichi Sakamoto, Haruo Sugiyama and Toshiki Yoshimine
The object of this study was to investigate the safety and clinical responses of immunotherapy targeting the WT1 (Wilms tumor 1) gene product in patients with recurrent glioblastoma multiforme (GBM).
Twenty-one patients with WT1/HLA-A*2402–positive recurrent GBM were included in a Phase II clinical study of WT1 vaccine therapy. In all patients, the tumors were resistant to standard therapy. Patients received intra-dermal injections of an HLA-A*2402–restricted, modified 9-mer WT1 peptide every week for 12 weeks. Tumor size, which was obtained by measuring the contrast-enhanced area on magnetic resonance images, was determined every 4 weeks. The responses were analyzed according to Response Evaluation Criteria in Solid Tumors (RECIST) 12 weeks after the initial vaccination. Patients who achieved an effective response continued to be vaccinated until tumor progression occurred. Progression-free survival and overall survival after initial WT1 treatment were estimated.
The protocol was well tolerated; only local erythema occurred at the WT1 vaccine injection site. The clinical responses were as follows: partial response in 2 patients, stable disease in 10 patients, and progressive disease in 9 patients. No patient had a complete response. The overall response rate (cases with complete or partial response) was 9.5%, and the disease control rate (cases with complete or partial response as well as those in which disease was stable) was 57.1%. The median progression-free survival (PFS) period was 20.0 weeks, and the 6-month (26-week) PFS rate was 33.3%.
Although a small uncontrolled nonrandomized trial, this study showed that WT1 vaccine therapy for patients with WT1/HLA-A*2402–positive recurrent GBM was safe and produced a clinical response. Based on these results, further clinical studies of WT1 vaccine therapy in patients with malignant glioma are warranted.