We performed a pilot study to investigate the safety and feasibility of autologous formalin-fixed tumor vaccine (ATFVac) and the clinical responses in glioblastoma multiforme (GBM) patients. GBM (WHO grade IV)
is the worst hard-to-treat malignant brain tumor.
Of the 12 patients,
8 had recurrent disease while 4 had been treated with regular radiation and chemotherapy but retained a visible tumor mass.
One showed a complete response, one showed a partial response, two showed minor responses, one had stable disease, and seven exhibited progressive disease.
The median overall survival period was 24 months from the primary resection, 10.7 months from the initiation of the AFTVac treatment but 3 of the 4 responders survived for 20 months or more after AFTVac inoculation.
The AFTVac therapy is safe and feasible, and could significantly improve the outcome of GBM.
REF: Ishikawa, E., Tsuboi, K.*, Yamamoto,. T., Muroi, A., Enomoto, T., Takano, S., Matsumura, A., Ohno, T., A clinical trial of autologous formalin-fixed tumor vaccine for glioblastoma multiforme patients. Cancer Sci., 98(8): 1226-1233, 2007. (*Corresponding author)
Overall survival from the primary resection
Overall survival from the AFTVac inoculation
<Background of Research and Development>
Glioblastoma multiforme (GBM) is currently treated with a combination of surgical removal, external beam radiotherapy, and nitrosourea chemotherapy. However, it is not overstating the case to say that GBM patients are never completely cured since most quickly suffer relapses and over 90% succumb within 5 years of diagnosis (1). Improving the outcome of GBM and extending the life span of GBM patients is thus a matter of great concern to clinicians.
With regard to current GBM therapies, it has been suggested that cytoreductive surgery may be beneficial (2, 3). However, others failed to detect significant differences in the survival of cases who had been subjected to different surgical modalities (4, 5). This has been attributed to the extreme diffuseness with which the tumor invades the brain parenchyma. In contrast, conventional x-ray radiotherapy at a dose of approximately 60 Gy has been found to be significantly beneficial, as it extends the median survival time by 18 weeks (6) or 5.6 months (7). In addition, a large-scale meta-analysis of the therapeutic effects of chemotherapy indicate that it extends survival by 2 months (8). Indeed, temozolomide chemotherapy was found to extend survival by only 2.5 months, resulting in the overall survival, 14.5 months after the primary resection (9).
The current inability to cure GBM has led to the development of various novel GBM therapies. In particular, there is growing interest in treatments that involve tumor-specific immune reactions because such treatments potentially have a high benefit-to-risk ratio. Moreover, these treatments may be useful in preventing tumor recurrence after initial localized treatments that involve surgery and radiotherapy. Indeed, our preliminary clinical studies have revealed that immunotherapeutic treatment of recurrent malignant glioma patients with ex vivo-expanded autologous tumor-specific T lymphocytes yields favorable results (10, 11).
However, this therapeutic approach suffers from a serious limitation, namely, the successful ex vivo-expansion of autologous tumor-specific T lymphocytes requires sufficient numbers of live tumor cells. This in turn necessitates the expansion of primary cultured tumor cells and the establishment of tumor cell lines (10, 11). These processes are generally time-consuming and tedious; moreover, tumor cells cannot always be successfully subcultured (12).
An alternative immunotherapeutic approach is to employ the formalin-fixed paraffin-embedded blocks of tumor tissues that are routinely prepared and stored after surgical removal.
Since formalin fixation preserves the specific antigenicity of tumor cells (13, 14, 15), these preparations could serve as an alternative tumor antigen source for cytotoxic T lymphocyte s (CTL) induction. Indeed, we have demonstrated that tumor-specific autologous CTLs can be generated by using several fixed sections; these cells have comparable activity and specificity to those induced by continuously cultured live tumor cells (14, 15).
Moreover, it has been shown that HLA-A2402-restricted carcinoembryonic antigen (CEA)-specific CTLs can be induced by culturing human peripheral blood mononuclear cells (PBMCs) with formalin-fixed (but not paraffin-embedded) autologous adhesive PBMCs loaded with CEA protein-bound latex-beads (16). Such CTLs could also be generated by using formalin-fixed adherent cells pulsed with 9- or 10-mer CEA-derived MHC-class I-presented tumor-associated antigens (TAA) (16).
The latter report further supports the notion that peptide TAAs derived from fixed cells or proteins are formalin-resistant. Thus, formalin-fixed and/or paraffin-embedded tumor cells/tissues may be useful TAA sources that can be employed to generate effective anti-tumor immune cells, as our laboratory has shown a case whose CTL were induced ex vivo on the formalin-fixed autologous GBM cells (see the case no. 1 in ref. 11).
Based on these observations, we previously constructed autologous formalin-fixed tumor vaccine (AFTV) from surgically extirpated tumor tissues (12, 13) and showed that these vaccines had a positive immunotherapeutic effect when tested with an experimental rat brain tumor model (17). In addition, retrospective (13) and prospective randomized clinical trials (18) have revealed AFTVac is efficacious in patients with hepatocellular carcinoma.
We recommend that, after the primary resection of the GBM, the patients should be treated with local radiation (60Gy), and then AFTVac (but not the standard chemotherapy, Temodar, before the AFTVac inoculation) for efficient induction of cytotoxic T lymphocytes in vivo. Chemotherapy may strongly inhibit these cellular immune responses.
If the patient had recurrence after the AFTVac, then treat the patient with the standard chemotherapy, Temodar, with frequent monitoring of peripheral blood lymphocytes. Hopefully, keep the lymphocyte level over 1000/uL to maintain potential cellular immune responses such as those with natural killer cells.
Note that, once lymphopenia was induced
by Temodar, full recovery of the lymphocyte number requires 5 months (median value)
after stopping Temodar (Su, Y.B., et al., Selective CD4+ lymphopenia in melanoma patients treated with temozolomide: a toxicity with therapeutic implications. J Clin Oncol. 22(4):610-616, 2004).
You can see the typical images of GBM patients (TEXTs were written in Japanese).