MGMT methylated (Met) patients (p) with glioblastoma (GBM) have a better prognosis with an earlier response (ER) than those who have a late response or pseudoprogression (LR/PsP). Results of the Gliocat study

Background

LR/PsP is more frequent in Met patients than in UnMet ones and it is considered an expression of therapeutic efficacy due to the combination with temozolomide and radiotherapy (TMZ&RT) of the Stupp's scheme. Our aim was to figure out if an ER at first evaluation (no PsP) was better or worse than a LR/PsP.

Methods

From the GLIOCAT study data base (432p) we identified those patients who had the first disease assessment within 60 days after the last day of concurrent TMZ&RT having further evaluations at 3/6 months or until progression while continuing on adjuvant TMZ treatment (256p). We defined ER as those patients without progression at first evaluation, and LR/ PsP as those that progressed at first evaluation but improved or maintained stable disease at subsequent evaluations.

Results

At first evaluation 128/256 (50%) p had an ER and 128/256 (50%) were at suspected progression (P); 56 of them improved at second and 4 at third evaluation (so 60 patients (23.5%) were considered as LR/PsP and 68 p (26.5%) were real P. PsP/LR was seen for any kind of initial surgery (0.12) and was more frequently seen in Met p (66%) than in unMet ones (34%). Conversely Met p had less real progressions (37.7%) than unMet p (62.3%) p = 0.01. All IDH1 mutated p (9) had ER (7) or PsP/LR (2) to treatment. Median Overall Survival (OS) was not different for patients with LR/PsP (17.9m) than those with ER (19.7); P = 0.48. (OS was only 12.3m for P patients). Nevertheless, Met p lived longer if they had ER (N = 45: 30.9m) than if they had LR/PsP (N = 33: 17.9m); P = 0.59. This held not true for unMet p: ER (N = 53: 18.0m) vs LR/PsP (N = 17: 17.9m); P = 0.44.

Conclusions

Although differences were not significant, our results suggest that LR/PsP does not increase survival and that it is a deleterious effect especially for Met p where it is more frequently observed. This should be explored in a larger series.

Clinical trial identification

Legal entity responsible for the study

N/A

Funding

Marató TV3

Disclosure

All authors have declared no conflicts of interest.