Primary central nervous system lymphoma, or PCNSL, is a rare lymphoma that sets up shop in the brain, spinal cord, eye, or cerebrospinal fluid without obvious disease elsewhere. That location matters. The brain is not just another organ with dramatic lighting. It sits behind the blood-brain barrier, which is less a picket fence and more a bouncer with a clipboard, a bad attitude, and zero interest in letting most drugs through. That is one reason PCNSL can be so hard to treat, especially after it comes back. Current reviews and guidelines still describe relapse as a major problem, even in the era of better chemotherapy and transplant strategies [2-4].
Which brings us to this new phase 1b study of rituximab, acalabrutinib, and durvalumab, charmingly compressed into the acronym RAD, as if oncology were trying to sound like a 1990s skateboard magazine [1].
Three tools, one very stubborn tumor
The logic of RAD is neat in the way biology occasionally allows before returning to chaos. Rituximab targets CD20 on B cells, which is like putting a bright orange sticker on the malignant cells that says, “Yes, these ones, please.” Acalabrutinib blocks Bruton's tyrosine kinase, or BTK, a key signal relay that many lymphoma cells use to keep themselves alive and self-important. Durvalumab blocks PD-L1, one of the molecular fake mustaches tumors use to tell the immune system, “Nothing to see here, officer.”
Why combine them? Because PCNSL is not just a pile of bad cells. It is a whole little political system. The tumor cells exploit B-cell signaling, the brain’s protected geography, and an immune microenvironment that too often behaves like security staff who somehow locked themselves outside the building. Reviews over the last few years have argued that both BTK signaling and immune escape are central parts of the disease, which makes this combination more than a random three-drug speed date [2-4].
What the trial actually found
This was a small, single-arm phase 1b study, so nobody should start composing victory fanfare just yet. Seventeen patients enrolled, most with relapsed or refractory disease, and 16 were evaluable for response. No dose-limiting toxicities showed up during the initial observation period, which is the clinical-trial equivalent of saying the bridge did not collapse during the ribbon-cutting ceremony [1].
The more interesting part is the efficacy signal. The overall response rate was 62.5%, and the complete response rate was 12.5%. Median progression-free survival was 4.3 months, and median overall survival was 11.9 months. All responders were treated at the higher acalabrutinib dose level, which hints that dose really matters here. The tradeoff, because cancer therapy refuses to let anyone have a simple week, was toxicity: 82% had treatment-related adverse events, and 59% had grade 3 or 4 events, including neutropenia, skin reactions, and elevated liver enzymes [1].
So no, this is not a miracle. It is something more useful than that word, which science should keep in a locked drawer. It is a plausible signal from a very difficult disease.
Why this feels bigger than one tiny trial
What makes the paper interesting is not only the response rate. It is the direction of travel. Over the past few years, PCNSL research has leaned harder into therapies that can actually function inside the CNS and exploit the disease’s biology rather than simply bludgeon it. BTK inhibitors have looked promising in recurrent disease, and newer studies combining targeted agents or checkpoint blockade with methotrexate-based therapy have produced encouraging results in other PCNSL settings [2-5].
A 2024 phase 2 trial of sintilimab with methotrexate, temozolomide, and rituximab reported very high response rates in newly diagnosed PCNSL, while a 2025 phase 2 study of rituximab, methotrexate, and orelabrutinib also showed strong activity [4,5]. Those are different populations and different regimens, so this is not apples to apples. More like apples to orbital mechanics. Still, the pattern is hard to miss: researchers are trying to turn PCNSL treatment from brute-force siege warfare into something more precise and biologically literate.
If RAD holds up in larger studies, the real-world payoff could be substantial. Patients with relapsed PCNSL do not need vague optimism. They need regimens that can reach the tumor, produce real responses, and maybe, just maybe, avoid torching the rest of the nervous system in the process. That is the practical dream here.
The sober bit, because somebody has to be the adult
This was an early-phase study with only 17 patients and no control arm. That means we cannot say RAD is better than other salvage approaches. We can say it is feasible, active enough to deserve more testing, and intellectually well-matched to what we now understand about PCNSL biology. In oncology, that is not the end of the story. It is the part where the scaffolding goes up and everybody argues about the next blueprint.
References
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Chang KY, Hsu YT, Chuang SS, et al. Rituximab, Acalabrutinib, and Durvalumab for Primary Central Nervous System Lymphoma: A Single-arm, Phase 1b, Multi-center Study. Clinical Cancer Research. 2026. DOI: https://doi.org/10.1158/1078-0432.CCR-25-3675
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Ferreri AJM, Calimeri T, Cwynarski K, et al. Primary central nervous system lymphoma. Nat Rev Dis Primers. 2023;9:46. DOI: https://doi.org/10.1038/s41572-023-00439-0
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Grommes C, DeAngelis LM. Primary central nervous system lymphoma. Blood. 2022;140(9):971-979. DOI: https://doi.org/10.1182/blood.2020008377
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Hoang-Xuan K, Deckert M, Ferreri AJM, et al. European Association of Neuro-Oncology (EANO) guidelines for treatment of primary central nervous system lymphoma (PCNSL). Neuro-Oncology. 2023;25(1):37-53. DOI: https://doi.org/10.1093/neuonc/noac196
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Zeng Z, Yang A, Yang J, et al. Sintilimab (anti-PD-1 antibody) combined with high-dose methotrexate, temozolomide, and rituximab (anti-CD20 antibody) in primary central nervous system lymphoma: a phase 2 study. Signal Transduct Target Ther. 2024;9:229. DOI: https://doi.org/10.1038/s41392-024-01941-x
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Li J, Liu Y, Xu W, et al. Prospective phase II trial of first-line rituximab, methotrexate, and orelabrutinib (R-MO) in primary central nervous system lymphoma. Blood Cancer Journal. 2025. DOI: https://doi.org/10.1038/s41408-025-01278-w
Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.