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

Publication date: Available online 31 January 2017
Source:Journal of Cranio-Maxillofacial Surgery
Author(s): Adepitan A. Owosho, Maria Thor, Jung Hun Oh, Nadeem Riaz, C. Jillian Tsai, Haley Rosenberg, Spyridon Varthis, Sae Hee K. Yom, Joseph M. Huryn, Nancy Y. Lee, Joseph O. Deasy, Cherry L. Estilo
BackgroundThe 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 MethodsSixty-three patients treated at the Memorial Sloan Kettering Cancer Center between 2006-2015, 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: <6 months; 2: 6-11 months; and 3: 12-24 months. Potential risk factors were investigated (Mann-Whitney U test), and relative risks (RRs) assessed for the two QUANTEC guidelines.ResultsThe incidence of xerostomia was 27%, 14% and 17% at follow-up time points 1, 2 and 3, respectively. At <6 months, the mean dose to the contralateral and the ipsilateral parotid glands (Dmeancontra, Dmeanipsi) was higher among patients with xerostomia (Dmeancontra: 25Gy vs. 15Gy; Dmeanipsi: 44Gy vs. 25Gy). Patients with xerostomia had higher pre-RT WMSFM (3.5g vs. 2.4g), and had been treated more frequently with additional chemotherapy (93% vs. 63%; all 4 variables: p<0.05). At 6-11 months, Dmeancontra among patients with xerostomia was higher compared to patients without (26Gy vs. 20Gy). The RR as specified by the one- and two-gland QUANTEC guideline was 2.3 and 1.4 for patients with <6 months follow-up time, and 2.0 and 1.2 for patients with longer follow-up (6-11 + 6-24 months).ConclusionXerostomia following IMRT peaks within six months post-radiotherapy and fades with time. Limiting the mean dose to both parotid glands (ipsilateral <25 Gy, contralateral <25 Gy) and reducing the use of chemotherapy will likely decrease the rate of xerostomia. Both QUANTEC guidelines are effective in preventing xerostomia.



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