The role of parotid gland irradiation in the development of severe hyposalivation (xerostomia) after intensity-modulated radiation therapy for head and neck cancer: Temporal patterns, risk factors, and testing the QUANTEC guidelines

Abstract Background The aims of this study were to investigate temporal patterns and potential risk factors for severe hyposalivation (xerostomia) after intensity-modulated radiotherapy (IMRT) for head and neck cancer (HNC), and to test the two QUANTEC (Quantitative Analysis of Normal Tissue Effects in the Clinic) guidelines. Patients and methods Sixty-three patients treated at the Memorial Sloan Kettering Cancer Center between 2006 and 2015, who had a minimum of three stimulated whole mouth saliva flow measurements (WMSFM) at a median follow-up time of 11 (range: 3–24) months were included. Xerostomia was defined as WMSFM ≤25% compared to relative pre-radiotherapy. Patients were stratified into three follow-up groups: 1: U test), and relative risks (RRs) assessed for the two QUANTEC guidelines. Results The incidence of xerostomia was 27%, 14% and 17% at follow-up time points 1, 2 and 3, respectively. At contra , Dmean ipsi ) was higher among patients with xerostomia (Dmean contra : 25 Gy vs. 15 Gy; Dmean ipsi : 44 Gy vs. 25 Gy). Patients with xerostomia had higher pre-RT WMSFM (3.5 g vs. 2.4 g), and had been treated more frequently with additional chemotherapy (93% vs. 63%; all 4 variables: p  contra among patients with xerostomia was higher compared to patients without (26 Gy vs. 20 Gy). The RR as specified by the one- and two-gland QUANTEC guideline was 2.3 and 1.4 for patients with Conclusion Xerostomia following IMRT peaks within six months post-radiotherapy and fades with time. Limiting the mean dose to both parotid glands (ipsilateral