The Survival Benefit of Postoperative Bacterial Infections in Patients With Glioblastoma Multiforme: Myth or Reality?

Surgical site infections after glioblastoma surgery: boon or bane?

BACKGROUND

Surgical site infections (SSIs) are among the most common postoperative complications. Glioblastoma multiforme is the most frequent malignant brain tumor with a dismal prognosis despite combined treatment. The effect of SSIs on the course of glioblastoma patients has not been fully clarified since available data are limited and partially contradictory. The aim of this study is to investigate the impact of SSIs on the course of patients with glioblastoma.

METHODS

The medical records of all patients undergoing surgery for glioblastoma between 2010 and 2020 in our institution were scanned and those with surgical site infections after glioblastoma resection were identified and compared to an age-matched control group. Overall survival and progression-free survival were the primary endpoints followed by the number of hospitalizations and the length of stay in hospital.

RESULTS

Out of 305 patients undergoing surgery for glioblastoma, 38 patients with postoperative surgical site infection after resection were identified and 15 (5 men and 10 women aged between 9 and 72) were included in this study. 23 patients were excluded. The control group consisted of 30 age-matched patients without SSI (18 men and 12 women). There were no significant differences in median overall survival. Progression-free survival was higher in the SSI group. The number of hospitalizations and the length of stay were significantly higher in the SSI group.

CONCLUSION

Our data suggest that SSIs might reduce early recurrences without affecting overall survival. Furthermore, they might decrease health-related quality of life by doubling the total length of hospital stay.

Prolonged survival in patients with local chronic infection after high-grade glioma treatment: Two case reports

High-grade gliomas are primary brain tumors with poor prognosis, despite surgical treatment followed by radiotherapy and concomitant chemotherapy. We present two cases of long-term survival in patients treated for high-grade glioma and concomitant prolonged bacterial wound infection. The first patient treated for glioblastoma IDH-wildtype had been without disease progression for 61 months from the first resected recurrence. Despite incomplete chemotherapy-induced myelosuppression in the second patient with anaplastic astrocytoma IDH-mutant, she died without disease relapse after 14 years from the diagnosis due to other comorbidities. We assume that the documented prolonged survival could be related to the bacterial infection.

Interaction between Bacteria and the Immune System for Cancer Immunotherapy: The α-GalCer Alliance

Non-conventional T cells, such as γδ T and invariant natural killer T (iNKT) cells, are emerging players in fighting cancer. Alpha-galactosylceramide (α-GalCer) is used as an exogenous ligand to activate iNKT cells. Human cells don’t have a direct pathway producing α-GalCer, which, however, can be produced by bacteria. We searched the literature for bacteria strains that are able to produce α-GalCer and used available sequencing data to analyze their presence in human tumor tissues and their association with survival. The modulatory effect of antibiotics on the concentration of α-GalCer was analyzed in mice. The human gut bacteria Bacteroides fragilis, Bacteroides vulgatus, and Prevotella copri produce α-GalCer structures that are able to activate iNKT cells. In mice, α-GalCer was depleted upon treatment with vancomycin. The three species were detected in colon adenocarcinoma (COAD) and rectum adenocarcinoma tissues, and Prevotella copri was also detected in bone tumors and glioblastoma tissues. Bacteroides vulgatus in COAD tissues correlated with better survival. In conclusion, α-GalCer-producing bacteria are part of the human gut microbiome and can infiltrate tumor tissues. These results suggest a new mechanism of interaction between bacteria and immune cells: α-GalCer produced by bacteria may activate non-conventional T cells in tumor tissues, where they can exert a direct or indirect anti-tumor activity.