Treatment effects of cumulative cisplatin dose during radiotherapy following induction chemotherapy in nasopharyngeal carcinoma: propensity score analyses

Background: The treatment effects of cumulative cisplatin dose (CCD) during radiotherapy (RT) following induction chemotherapy (IC) have not been determined for patients with locoregionally advanced nasopharyngeal carcinoma (NPC). Methods: A total of 3460 patients with locoregionally advanced NPC who were treated with IC plus cisplatin-based concurrent chemoradiotherapy or RT alone were included in this retrospective study. Three CCD groups (0 mg/m(2) <= CCD <100 mg/m(2), 100 mg/m(2) <= CCD <200 mg/m(2), CCD > 200 mg/m(2)) were balanced through the inverse probability of treatment weighting based on propensity scores estimated by a general boosted model. The primary endpoint was overall survival (OS); the secondary endpoints were distant metastasis-free survival (DMFS) and locoregional recurrence-free survival (LRFS). Results: CCD > 200 mg/m(2)and <200 mg/m(2)exhibited similar treatment effects for OS and DMFS, and were both superior to CCD <100 mg/m(2)for OS and DMFS in patients with stage IVa NPC. The three CCD groups achieved similar treatment effects for patients with stage II-III NPC. After IC, CCD during RT appeared to exert little treatment effect on LRFS. Conclusion: The CCD during RT exerts treatment effects and improves OS by reducing the risk of distant metastasis for patients with stage IVa NPC following IC, and CCD <200 mg/m(2)(mainly 160 mg/m(2)in this group) is recommended. However, RT alone may be sufficient after IC in patients with stage II-III NPC.