1282 - Clinical Outcomes of Reduced-Dose Whole-Brain Radiotherapy After Induction Chemotherapy for Primary Central Nervous System Lymphoma: A Retrospective Single-Institution Study

09:17am - 09:23am ET

Room 254

Presenter(s)

Hiroaki Ogawa, MD - Miyagi Cancer Center, Miyagi, Miyagi

H. Ogawa¹, M. Kozumi¹, M. Kubozono¹, and K. Jingu²; ¹Department of Radiation Oncology, Miyagi Cancer Center, Miyagi, Japan, ²Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan

Purpose/Objective(s):

To mitigate neurotoxicity, reduced-dose whole-brain radiotherapy (rdWBRT) of 23.4 Gy has been used at our institution as consolidation therapy for patients with primary central nervous system lymphoma (PCNSL) after induction chemotherapy since 2016. We retrospectively assessed treatment outcomes in a real-world clinical setting.

Materials/Methods:

Patients with PCNSL who were treated with curative-intent radiotherapy including rdWBRT were retrospectively reviewed. Induction chemotherapy consisted of R-MPV (rituximab, methotrexate, procarbazine, and vincristine) up to seven cycles, followed by two cycles of high-dose cytarabine administered as consolidation after radiotherapy. Patients without complete response (CR) after induction chemotherapy received an additional focal tumor boost to a total dose of 45 Gy.

Progression-free survival (PFS), intracranial control (IC), overall survival (OS) and chronic adverse events were evaluated. Survival outcomes were estimated using the Kaplan–Meier method.

Results:

A total of 112 patients were included. Median follow-up was 35 months (range, 1–117 months), and median age was 69 years (range, 33–87). Performance status (PS) was 0, 1, and 2–4 in 40, 39, and 33 patients, respectively. Pathological diagnosis was obtained in 98 patients, including 97 B-cell lymphomas. Ocular involvement was observed in 10 patients and 27 patients had multifocal diseases. Induction chemotherapy was administered in 109 patients, with a median of five cycles (range, 1-7). Responses after induction chemotherapy were CR in 74 patients (66.1%), partial response in 24 (21.4%), stable disease in 1 (0.9%), and progression disease in 10 (8.9%), respectively.

The 3-year PFS, IC, and OS rates were 58.3% (median, 61 months), 65.9% (median not reached), and 77.6% (median not reached), respectively. Thiry-six cases experienced relapse, occurring intracranially in 27 patients, in the spinal canal or eye in 11, and extracranially in 7, with some overlap. On univariate analysis, number of chemotherapy cycles, response after induction chemotherapy, and PS were associated with PFS; however, no factors remained significant on multivariate analysis. No grade =3 chronic neurotoxicity was clinically documented based on medical record review. Notably, formal neurocognitive testing was not routinely performed, limiting quantitative assessment of late neurocognitive outcomes.

Conclusion:

Reduced-dose WBRT following induction chemotherapy provided durable disease control and favorable survival outcomes in a real-world PCNSL cohort. These findings support rdWBRT as an effective consolidative strategy. Further investigation of neurocognitive outcomes is warranted.