Gamma knife stereotactic radiosurgery as an effective tool in primary CNS lymphoma: Evaluation of stereotactic radiosurgery and methotrexate treatment in a prospective and observational clinical research study.

Objective: The purpose of this study was to compare the progression of Primary Central Nervous System Lymphoma (PCNSL) in patients treated with methotrexate (MTX) versus those treated with a combination of Stereotactic Radiosurgery (SRS) and MTX. Progression was measured via brain lesion count and tumor volume.

Methods: This observational and prospective cohort study evaluated the outcome of SRS treatment of PCNSL in one hundred twenty-eight subjects. We analyzed baseline, prospective, and retrospective data of patients enrolled in the brain tumor registry between June 2010 and August 2017. Seventy-three patients were treated exclusively with MTX while the remaining fifty-five patients received a combination of SRS and MTX. Strict inclusion and exclusion criteria were established.

Results: Mean survival rate for patients receiving combined SRS and MTX treatment was significantly higher (52.6 months) compared to the MTX group (19.8 months); p = 0.0029. At the 36 months follow-up, patients treated with SRS and MTX also had a lower rate of tumor progression (32.7 %) than the MTX group (95.9 %); p = 0.00192. Local tumor control was achieved in all patients treated with SRS. No clinical toxicity was observed in this group.

Conclusions: Clinical results obtained from this observational study highlight the potential effectiveness of SRS in the treatment of PCNSL. Although treatment outcomes have improved in the past years, additional evidence in the clinical design of randomized trials is needed to evaluate the strength of this treatment in specific situations.