Feasibility and Efficacy of Individualized Radiation Therapy for Primary Central Nervous System Lymphoma: Radiation Treatment Planning According to Treatment Response by Radiographic Assessment.

Abstract

Background: To assess the feasibility and efficacy of individualized treatment selection in radiation therapy (RT) for primary central nervous system lymphoma (PCNSL) according to treatment response by radiographic assessment. Methods: The details of recurrence and change in performance status (PS) were assessed in 31 patients with histologically confirmed PCNSL treated between 2000 and 2016. During the treatment period, radiographic assessment was conducted, and RT planning (RTP) was determined individually by treatment response. Results: At a median follow-up of 28.2 months, 9 patients were alive and 7 of whom were relapse-free. Two-year overall survival (OS) and progression-free survival (PFS) rates were 69.3% and 52.7%, with median survival times (MSTs) of 36.5 months and 24.4 months, respectively. Two-year local recurrence rate was 40.5% and the median time to local recurrence from treatment initiation was 27.9 months. All patients were scheduled to receive whole-brain RT (WBRT) and subsequent partial-brain RT(PBRT), with a median total dose to the tumor bed of 46 Gy and median WBRT dose of 30 Gy. Eight patients received reduced-dose WBRT (rd-WBRT) (<30 GY), and 13 patients who could not achive a complete response (CR) during the RT period received additional boost radiation after WBRT and PBRT, with a median dose of 6 Gy. Over 70% of local recurrence occurred within areas in which only WBRT was conducted (median dose of 30.3 Gy). Two-year occurrence rate of neurotoxicity over grade 2 was 49.5%. PS at 24 months after RT was maintained in 12 patIents. Conclusions: lndividual RTP using radiographic assessment led to reasonable survival and disease control rates with mild treatment-related toxicity. For patients not receiving chemotherapy or lacking a CR after chemotherapy and WBRT, WBRT followed by PBRT and additional boost radiation for poor RT responders might be effective. However, even for patients with CR after chemotherapy, a WBRT dose of 30 Gy or higher might be necessary for local control.