Proton beam therapy for skull base chordomas: a systematic review of tumor control rates and survival rates

The management of base of skull (BS) chordomas is a neurosurgical conundrum owing to their close proximity to the critical neurovascular structures. Surgical resection is the gold standard treatment followed by adjuvant radiotherapy which includes photon therapy, proton beam therapy (PBT), gamma knife radiosurgery, etc. PBT has become an unparalleled therapeutic modality in the management of BS chordomas. The aim of this systematic review was to assess the outcomes in BS chordoma patients who received PBT as a primary or adjuvant therapy. PubMed and Cochrane databases were screened till May 2022. Following the PRISMA guidelines, studies were reviewed thoroughly, and the data of the included study was extracted. Statistical analysis was performed using the SAS 9.4 with P value .05 considered as significant. Sixteen studies with 752 patients were included. The majority of the patients were adults ( 18 years) with a male:female ratio of 1.2. The most common clinical features were cranial nerve (3rd, 6th, or 12th) palsy and hearing impairment. Ninety-five percent of the patients underwent surgical resection before PBT. The mean PBT dose received was 74.02 cGe (cobalt gray equivalent). Eighty percent of the patients showed a positive response to the therapy defined in terms of tumor regression. Five-year local control (LC), overall survival (OS), and progression-free survival (PFS) were calculated as 76.6%, 79.6%, and 89%, respectively. Statistical analysis revealed none of the factors had any significant association with 5-year LC. PBT is a growing therapeutic technique that has revolutionized the treatment of BS chordomas.