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.