812MO - Initial results of the multicenter phase II trial of a novel hypofractionated low-dose radiotherapy for indolent non-Hodgkin lymphoma

Background

Indolent non-Hodgkin lymphoma (iNHL) has been shown to be highly radiosensitive, and the most effective radiotherapy (RT) regimen has yet to be established. Recent findings suggested that hypofractionated RT may have a more pronounced antitumor effect. We therefore conducted a phase 2 trial to evaluate the efficacy and toxicity of dose-deescalated hypofractionated radiotherapy in patients with iNHL.

Methods

The study design was a multicenter, single-arm, phase 2 trial with a planned accrual of 73 sites. Patients with indolent non-Hodgkin lymphoma aged 18 years or older, without a history of prior radiotherapy at the same site, were deemed eligible for the study. Involved-site radiotherapy was delivered at 12 Gy in four fractions within one week. The primary endpoint was the complete response (CR) rate per RECIL 2017 by investigators at 6 months after radiotherapy. Secondary endpoints were 6-month overall response rate (ORR), 2-year progression-free survival, 2-year local control rate, acute and late toxicity, quality of life (QOL), and immunologic biomarkers induced by hypofractionated radiotherapy.

Results

A total of 73 sites from 71 patients were enrolled between May 8, 2022, and November 8, 2023, at three centers in China. The median age was 54 years (interquartile range [IQR], 47-64), with a male-to-female ratio of 1:1.43. Most patients (82.2%) had Ann Arbor stage I to II diseases. The most common subtype was marginal zone lymphoma (n = 55; 75.3%). With a median follow-up of 10.5 months (range, 6.0-23.9), the 6-month CR and ORR rates were 93.2% and 100%, respectively. Acute toxicities were minimal, with no grade 3 or greater adverse events. The most frequent grade 1 or 2 adverse events were lymphocytopenia (30.1%), and nausea (20.5%), with 79.8% of events occurring within 2 weeks following the completion of radiotherapy.

Conclusions

Hypofractionated low-dose radiotherapy of 12 Gy in 4 fractions demonstrated promising antitumor activity among patients with iNHL. No severe toxicity was observed in the novel regimen. Long-term follow-up is required to assess the durability of tumor control, late toxicity, dynamic QOL, and immune biomarkers.

Clinical trial identification

NCT05543070.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.