Impact on xerostomia for nasopharyngeal carcinoma patients treated with superficial parotid lobe-sparing intensity-modulated radiation therapy (SPLS-IMRT): A prospective phase II randomized controlled study

Purpose To compare the incidence of xerostomia in nasopharyngeal carcinoma (NPC) patients treated with superficial parotid lobe–sparing intensity-modulated radiation therapy (SPLS-IMRT) and conventional IMRT (C-IMRT). Methods Patients with histologically confirmed NPC who met the eligibility criteria were randomly assigned to receive either SPLS-IMRT or C-IMRT. The primary endpoint was the incidence of xerostomia at 12 months post-IMRT. The secondary endpoints included the xerostomia questionnaire (XQ) score, unstimulated salivary flow rate (USFR), stimulated salivary flow rate (SSFR), and survival outcomes. Results Ninety patients were enrolled. Eighty-two patients were included for xerostomia analysis (42 in the SPLS-IMRT group and 40 in the C-IMRT group). At 12 months post-IMRT, the incidence of xerostomia in the SPLS-IMRT group was significantly lower than that in the C-IMRT group (83.4% vs 95.0%; P = 0.007), especially the grade 3 xerostomia (0% vs 12.5%; P < 0.001). The median change in XQ score was similar between the two groups (11.9 points vs 14.1 points; P = 0.194). There was a significantly higher median fractional USFR (0.67 vs 0.35; P = 0.024) and SSFR (0.66 vs 0.32; P = 0.021) in the SPLS-IMRT group than the C-IMRT group. The 3-year LRRFS, DMFS, and OS in the SPLS-IMRT and C-IMRT groups were 92.5% vs 90.9%, 83.8% vs 81.7%, and 88.9% vs 88.2% (all P > 0.05). Conclusion SPLS-IMRT significantly reduced the incidence of xerostomia at 12 months post-IMRT in NPC by recovering parotid gland function earlier than C-IMRT, without compromising survivals. Phase III clinical trials are warranted. (ClinicalTrials.gov, number NCT05020067)