38P - Locoregional radiotherapy improves survival outcomes in de novo metastatic nasopharyngeal carcinoma treated with chemoimmunotherapy

Background

We aimed to investigate the efficacy of locoregional radiotherapy (LRRT) in patients with de novo metastatic nasopharyngeal carcinoma (dmNPC) receiving chemotherapy combined with anti-programmed cell death receptor-1 monoclonal antibodies (anti-PD-1 mAbs) as first-line treatment and to identify optimal LRRT candidates based on Epstein-Barr Virus DNA (EBV DNA).

Methods

We enrolled patients with dmNPC receiving platinum-based palliative chemotherapy and anti-PD-1 mAbs followed or not followed by LRRT from four centers. The endpoints were progression-free survival (PFS), objective response rate (ORR), and overall survival (OS). Additionally, we used the inverse probability of treatment weighting (IPTW) to balance baseline characteristics of the LRRT and no-LRRT groups to minimize selection bias before the comparative analyses. Multivariate analyses were performed using the Cox proportional hazards model.

Results

We included 163 patients with dmNPC (median follow-up: 22 months). The median PFS was 20 months, and the ORR was 69.2%; the median OS was not achieved. After the IPTW adjustments, patients who received LRRT had a significant survival benefit over those who did not receive LRRT (median PFS: 28 months vs. 14 months; ORR: 81.0% vs. 48.3%; all P <0.001). The EBV DNA level after four to six cycles of anti-PD-1 mAbs (weighted hazard ratio [HR]: 2.01, 95% confidence interval [CI]: 1.11−3.65, P = 0.02) and LRRT (weighted HR: 0.58, 95% CI: 0.34−0.99, P = 0.04) were independent prognostic factors. Patients with undetectable EBV DNA levels after four to six cycles of anti-PD-1 mAbs (early EBV DNA clearance) benefitted from LRRT (HR: 0.43, 95% CI: 0.23−0.80, P = 0.007), whereas patients with detectable levels did not (HR: 1.03, 95% CI: 0.47−2.26, P = 0.93).

Conclusions

Palliative chemotherapy combined with anti-PD-1 mAbs followed by LRRT was associated with improved survival outcomes in patients with dmNPC, especially for patients with early EBV DNA clearance.

Clinical trial identification

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.