Immunotherapy in Metastatic Brain Tumors; Where do we stand?
Mohyeldin S Abdelhalim1#, Malak Munir2#, Ibrahim ElGarhy2, Ahmed Sayed2, Ahmed Bayoumi3, Eshak I Bahbah4, Mohammad Aladawi5, Mohamed Elfil5*
1Department of Clinical Oncology, Faculty of Medicine, Alexandria University, Alexandria, Egypt, 2Faculty of Medicine, Ain Shams University, Cairo, Egypt, 3Department of Neurology, McGovern Medical School, Houston, Texas, USA, 4Faculty of Medicine, Al-Azhar University, Damietta, Egypt, 5Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, Nebraska, USA
The management of brain tumors poses as a challenging endeavor due to a multitude of factors including the special nature of the organ and the origins of neoplasms affecting it. Armed with a limited arsenal of treatment options, we are pushed to seek novel management approaches. Immune checkpoint inhibitors (ICIs) have recently shown remarkable promise in the management of several aggressive neoplasms such as malignant melanoma and non-small cell lung carcinoma, both commonly implicated in brain metastasis. ICIs induce immune response against the neoplastic cells by several mechanisms.
The brain has its own unique immune niche which affects the local immune response against neoplastic cells; in addition to that metastatic neoplastic cells has its own role in inhibiting a proper immune response against them.
Despite showing underwhelming efficacy in the management of glioma ICIs showed positive outcomes in secondary brain tumors. Several treatment regiments were described in the literature as consolidative to chemotherapeutic agents, or a standalone therapy. Notably, ICIs showed efficacy in the management of brain metastasis secondary to malignant melanoma and non-small cell lung carcinoma.
In this article, we review the studies that investigated the use of ICIs in the management of primary and secondary brain tumors with special emphasis on the ones originating from non-small cell lung carcinoma and renal cell carcinoma. Also, it highlights the need to study a more representative population as this novel approach could improve upon the current patient outcomes.