Outcomes of combined immunotherapy and palliative radiotherapy in patients with recurrent/metastatic head and neck cancers.

e18002 Background: Immunotherapy has revolutionized the treatment for recurrent/metastatic head and neck cancers (R/M HNC). It is uncertain whether the combination of immunotherapy and radiotherapy can provide survival benefits for R/M HNC. Methods: This study included patients with R/M HNC who underwent immunotherapy in our institute from November 2018 to October 2022. All patients received intravenous PD-1 inhibitors every 3 weeks. Palliative radiotherapy was administered to localized lesions for symptomatic treatment purposes in addition to systemic therapies. Tumor response was evaluated using RECIST1.1 criteria. The primary outcome measures were progression-free survival (PFS) and overall survival (OS). Other outcome measures were disease control rate (DCR) and objective response rate (ORR). The Kaplan-Meier method was utilized for survival analysis, and univariate and multivariate Cox regression analysis was conducted to identify prognostic factors associated with PFS and OS. Results: We included 129 R/M HNC patients. The median follow-up time was 14.0 months. The median number of immunotherapy courses received was 4 (range: 1-60). During immunotherapy, 43 patients received palliative radiotherapy, targeting primary tumors, lymph nodes, metastasis in liver, lung, bone, and other sites. Following the treatments, 16 (12.4%) patients achieved complete response (CR), 44 (34.1%) achieved partial response (PR), 35 (27.1%) had stable disease (SD), and 34 (26.4%) had progressive disease (PD). The ORR was 46.5% and the DCR was 73.6%. The group receiving immunotherapy combined with palliative radiotherapy had higher ORR (65.1% vs 37.2%, p = 0.005) and DCR (90.7% vs 65.1%, p = 0.004) than those without palliative radiotherapy. The PFS (15.0 months vs 4.0 months, p = 0.0027) and OS (not reached vs 26.0 months, p = 0.036) were improved in patients receiving palliative radiotherapy compared to those not. Patients who had received prior radiotherapy (n = 81) had a shorter PFS (4.0 months vs 14.0 months, p = 0.014), while there was no difference in OS (p = 0.16). We further showed that patients had better PFS (20.0 months vs 2.0 months; p < 0.0001) and OS (43 months vs 17 months; p = 0.0043) when they received more than 4 cycles of immunotherapy. At the same time, our findings demonstrated that immunotherapy combined with nanoparticle albumin‐bound (nab-) paclitaxel-based regimens may prolong PFS (14.0 months vs 4.0months vs 2.5months, p = 0.0055) than gemcitabine-based regimens and other regimens. Conclusions: In patients with R/M HNC, the combination of immunotherapy and palliative radiotherapy demonstrates a synergistic effect, resulting in survival benefits. Prior radiotherapy might compromise patients’ PFS. Increasing the number of immunotherapy cycles and combining with nab-paclitaxel chemotherapy may improve patient survival.