Efficacy and Safety of Pulsed Low-Dose Rate Radiotherapy in Re-Irradiation of Recurrent Solid Tumors: A Single-Center Retrospective Study.

OBJECTIVE

To evaluate the efficacy and safety of pulsed low-dose rate (PLDR) radiotherapy in the re-irradiation of recurrent solid tumors.

METHODS

This retrospective analysis was conducted on 64 patients with recurrent solid tumors who received PLDR re-irradiation. The treatment regimen consisted of 0.4 Gy per pulse, administered 5 times daily with a 5-minute interval, to a total dose of 20 to 66 Gy. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and treatment-related toxicities were assessed, with subgroup analysis performed by cancer type.

RESULTS

As of May 2025, the ORR was 53.13% (34/64), and the DCR was 85.94% (55/64). The median OS and PFS were 12.80 months and 7.10 months, respectively. Treatment-related toxicities were primarily grades 1 to 2, with a low incidence of grade 3 events and no grade ≥4 events. In the glioma subgroup (n=27), ORR reached 62.96% with a 14.81% complete response rate. Univariate analysis identified IDH1 mutation, nontemporal lobe recurrence, and a re-irradiation interval >24 months as favorable prognostic factors. Multivariate Cox regression confirmed IDH1 mutation as an independent protective factor for both OS (HR=0.15, P<0.01) and PFS (HR=0.24, P<0.01). A re-irradiation interval >24 months was protective for OS (HR=0.23, P=0.02), while temporal lobe recurrence was a risk factor for PFS (HR=4.00, P=0.03).

CONCLUSION

PLDR re-irradiation demonstrates favorable efficacy and safety in recurrent solid tumors. For recurrent glioma, patients with IDH1 mutation, nontemporal lobe recurrence, and a re-irradiation interval >24 months appear to derive greater benefit from PLDR radiotherapy.