Immunologic escape after prolonged progression-free survival with epidermal growth factor receptor variant III peptide vaccination in patients with newly diagnosed glioblastoma

Abstract

Purpose: Immunologic targeting of tumor-specific gene mutations may allow precise eradication of neoplastic cells without toxicity. Epidermal growth factor receptor variant III (EGFRvIII) is a constitutively activated and immunogenic mutation not expressed in normal tissues but widely expressed in glioblastoma multiforme (GBM) and other neoplasms.

Patients and methods: A phase II, multicenter trial was undertaken to assess the immunogenicity of an EGFRvIII-targeted peptide vaccine and to estimate the progression-free survival (PFS) and overall survival (OS) of vaccinated patients with newly diagnosed EGFRvIII-expressing GBM with minimal residual disease. Intradermal vaccinations were given until toxicity or tumor progression was observed. Sample size was calculated to differentiate between PFS rates of 20% and 40% 6 months after vaccination.

Results: There were no symptomatic autoimmune reactions. The 6-month PFS rate after vaccination was 67% (95% CI, 40% to 83%) and after diagnosis was 94% (95% CI, 67% to 99%; n = 18). The median OS was 26.0 months (95% CI, 21.0 to 47.7 months). After adjustment for age and Karnofsky performance status, the OS of vaccinated patients was greater than that observed in a control group matched for eligibility criteria, prognostic factors, and temozolomide treatment (hazard ratio, 5.3; P = .0013; n = 17). The development of specific antibody (P = .025) or delayed-type hypersensitivity (P = .03) responses to EGFRvIII had a significant effect on OS. At recurrence, 82% (95% CI, 48% to 97%) of patients had lost EGFRvIII expression (P < .001).

Conclusion: EGFRvIII-targeted vaccination in patients with GBM warrants investigation in a phase III, randomized trial.

Fig 1.

Axial magnetic resonance images showing progression of multiple lesions surrounding the corpus callosum. Left: T1-weighted, contrast-enhanced image 8 months from first vaccination showing new enhancing lesions distant from the right frontal tumor cavity. Right: T2-weighted image showing hyperintense lesion in similar distribution. Areas of contrast-enhancement have resolved, but areas of T2 hyperintensity have persisted.

Fig 2.

(A) Progression-free survival (PFS). Left: The median PFS from histologic diagnosis in the patients who had been vaccinated (n = 18; solid blue line) was 14.2 months (95% CI, 9.9 to 17.6 months). Dotted blue lines show 95% CIs. Right: In the temozolomide (TMZ) -treated historical cohort (n = 17; gold line), the median PFS was 6.3 months (95% CI, 4.1 to 9.0 months). The PFS of patients who had been vaccinated compares favorably with that of the TMZ-treated cohort before (P = .013) and after (P = .041) adjustment for age and Karnofsky performance status (KPS). (B) Overall survival (OS). Left: The median survival of patients who had been vaccinated (n = 18; solid blue line) was 26.0 months (95% CI, 21.0 to 47.7 months;). Dotted blue lines show 95% CIs. Right: In the TMZ-treated historical cohort (n = 17; gold line), the median survival was 15.0 months (95% CI, 11.4 to 19.7 months). The OS of patients who had been vaccinated compares favorably with that of the TMZ-treated cohort before (P = .002) and after (P = .001) adjustment for age and KPS. EGFRVIII, epidermal growth factor receptor variant III.

Fig 3.

Epidermal growth factor receptor (EGFR) and EGFR variant III (EGFRvIII) immunohistochemistry of a patient with glioblastoma multiforme (GBM). Staining with (A) EGFR and (B) EGFRvIII before vaccine. (C) Preservation of EGFR staining but (D) specific loss of EGFRvIII staining at recurrence after vaccination.

Fig 4.

Immune response correlates. Overall survival (OS) from histologic diagnosis for all patients for whom serum was available to test for epidermal growth factor receptor variant III (EGFRvIII) –specific antibody titers (n = 14; left) and delayed-type hypersensitivity (DTH; n = 17; right). The blue line shows patients with EGFRvIII-specific immune responses, and the gold line shows patients without EGFRvIII-specific responses. Left: The median OS for the six patients who developed EGFRvIII-specific antibody responses was 47.7 months (95% CI, 20.8 to ∞ months). For the eight patients who did not develop antibody responses, the OS was only 22.8 months (95% CI, 21.0 to 34.9 months). After adjustment for age, Karnofsky performance status, and methylguanine methyltransferase methylation, the OS from vaccination of the patients who developed antibody responses was found to be greater (hazard ratio, 0.08; 95% CI, 0.007 to 0.93; P = .043). Right: The median OS for the three patients who developed DTH responses specific for PEPvIII (a 13-amino-acid peptide with an additional terminal cysteine that spans the EGFRvIII mutation) has not been reached at 50 months. For the 14 patients who did not develop DTH responses to PEPvIII, the OS was 23.1 months (95% CI, 21.0 to 44.1 months). Patients who developed PEPvIII DTH responses had a significantly longer OS (P = .03).

Fig A1.

Progression-free survival (PFS) from histologic diagnosis for all patients for whom methylguanine methyltransferase (MGMT) methylation status could be assessed is shown (n = 13). The blue line shows patients with unmethylated MGMT (n = 7) who had a median PFS of 22.0 months (95% CI, 14.9 to ∞ months), and the gold line shows patients with methylated MGMT (n = 6) who had a median survival of 10.9 months (95% CI, 6.5 to 15.4 months). When adjusted for age and Karnofsky performance status, patients who had been vaccinated with unmethylated MGMT had an unexpectedly significantly longer PFS (hazard ratio, 0.17; 95% CI, 0.032 to 0.90; P = .037).