Abstract 664: Surgery plus adjuvant radiation as a valid treatment option for primary central nervous system lymphoma (PCSNL)
Authors: Kinslow Connor J. , Rae Ali I. , Neugut Alfred I. , Adams Christopher M. , Sheth Sameer A. , McKhann Guy M. , Sisti Michael B. , Bruce Jeffrey N. , Iwamoto Fabio M. , Sonabend Adam M. , Wang Tony J. 
Published: August 2018

Abstract
Background: Recent studies of primary central nervous system lymphoma (PCNSL) have found an association between cytoreductive surgery and survival, challenging the traditional notion that surgery is not beneficial and potentially harmful. However, no studies have examined outcomes after surgery plus adjuvant treatment. We investigated treatment-related outcomes for surgery plus radiation using data from the Surveillance, Epidemiology, and End Results (SEER) Program.
Methods: The SEER database was queried to collect cases of histologically confirmed non-Hodgkin's lymphoma within the CNS diagnosed between 1995-2014. Median survival times were determined by the Kaplan-Meier method and compared using the log-rank test. Predictors of overall survival and cause-specific survival were determined using the Cox proportional hazards regression model. Treatment modalities were categorized as biopsy alone, biopsy plus radiation therapy (RT), surgery alone, and surgery + RT. Biopsy alone was used as the reference category. Subgroup analysis stratified patients by extent of surgical resection and recursive partition analysis (RPA) risk group.
Results: We identified 5,417 cases that met search criteria, 39% of which received surgical resection. Median survival times for biopsy alone (n=1,824, 34%), biopsy + RT (n=1,460, 27%), surgery alone (n=1,222, 23%), and surgery + RT (n=911, 17%) were 7, 8, 20, and 27 months, respectively (p&lt;0.0001). On multivariable analysis, RT after surgery was associated with a 13% incremental increase in overall survival (Hazard Ratio [HR]=0.71, p&lt;0.0001 vs. HR=0.58, p&lt;0.0001). When analyzing by extent of resection, median survival times for subtotal resection alone (n=111, 2%), gross-total resection alone (n=583, 11%), subtotal resection + RT (n=98, 2%), and gross-total resection + RT (n=459, 8.5%) were 10, 20, 20, and 27 months, respectively (p&lt;0.0001). RT after surgery was independently associated with increased survival in the gross-total resection subgroup (HR=0.85, p=0.046) and in all patients who received surgery (HR=0.87, p=0.017). RT after surgery was also associated with an incremental increase in survival in the RPA class I (HR=0.47, p&lt;0.0001 vs. 0.40, p&lt;0.0001) and class II-III (HR=0.77, p&lt;0.0001 vs. HR=0.66, p&lt;0.0001) subgroups. All findings were confirmed by multivariable analysis of cause-specific survival.
Conclusion: Surgical resection of PCNSL in the general population is more common than previously thought. Radiation therapy after surgery is associated with increased survival, regardless of the extent of surgical resection or the patient's RPA risk category. Neurotoxicity, dosing, and effects of concurrent chemotherapy should be addressed in future studies.
Citation Format: Connor J. Kinslow, Ali I. Rae, Alfred I. Neugut, Christopher M. Adams, Sameer A. Sheth, Guy M. McKhann, Michael B. Sisti, Jeffrey N. Bruce, Fabio M. Iwamoto, Adam M. Sonabend, Tony J. Wang. Surgery plus adjuvant radiation as a valid treatment option for primary central nervous system lymphoma (PCSNL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 664.