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 ⩽ CCD <100 mg/m, 100 mg/m ⩽ CCD <200 mg/m, CCD ⩾200 mg/m) 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 and <200 mg/m exhibited similar treatment effects for OS and DMFS, and were both superior to CCD <100 mg/m 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 (mainly 160 mg/m in this group) is recommended. However, RT alone may be sufficient after IC in patients with stage II-III NPC.