Efficacy of local-regional radiotherapy in de novo metastatic nasopharyngeal carcinoma patients receiving chemo-immunotherapy: A multicenter, propensity score matching study.

Background: To evaluate the efficacy of local-regional radiotherapy (LRRT) in de novo metastatic nasopharyngeal carcinoma (dm NPC) patients receiving chemo-immunotherapy as first-line treatment and select the beneficiaries from LRRT.

Methods and materials: M1-NPC patients receiving platinum-based chemo-immunotherapy with or without LRRT from four centers were included in this study. The propensity score matching (PSM) analysis was employed to balance the baseline characteristics between the LRRT and non-LRRT groups.

Results: 546 dm NPC patients (140 patients in the non-LRRT group and 406 patients in the LRRT group) were incorporated. Patients receiving LRRT demonstrated significantly improved progression-free survival (3-year PFS rate, 53.2 % vs 31.2 %, p < 0.001). After PSM analysis, there were 244 patients in the LRRT group and 122 patients in the non-LRRT group. Multivariable analysis indicated that LRRT was not an independent prognostic factor in the matched cohort (HR, 1.25, 95 % CI, 0.92-1.69, p = 0.156). Subgroup analysis among the matched cohort showed a significant increase in PFS for patients with oligo metastatic disease (OMD) who received LRRT (3-year PFS rate, 70.6 % vs 49.3 %, p = 0.043). In contrast, no such benefit was observed in patients with poly metastatic disease (PMD, 3-year PFS rate, 35.8 % vs 27.8 %, p = 0.17). Furthermore, LRRT significantly enhanced survival in patients with undetectable EBV DNA_{2-6 cycles} (3-year PFS rate, 57.9 % vs. 43.4 %, p = 0.043), whereas no survival improvement was noted in patients with detectable EBV DNA_{2-6 cycles} (16.2 % vs. 20.3 %, p = 0.21).

Conclusion: LRRT could prolong PFS in M1-NPC patients. OMD and undetectable EBV DNA_{2-6 cycles} are potential indicators for selecting beneficiaries from LRRT.