Internal and external generalizability of temporal dose–response relationships for xerostomia following IMRT for head and neck cancer. Issue 2 (February 2017)

• Record Type: Journal Article
• Authors: Thor, Maria; Owosho, Adepitan A.; Clark, Haley D.; Oh, Jung Hun; Riaz, Nadeem; Hovan, Allan; Tsai, Jillian; Thomas, Steven D.; Yom, Sae Hee K.; Wu, Jonn S.; Huryn, Joseph M.; Moiseenko, Vitali; Lee, Nancy Y.; Estilo, Cherry L.; Deasy, Joseph O.
• Is Part Of: Radiotherapy and oncology. Volume 122:Issue 2(2017:Feb.)
• Page Start: 200
• Page End: 206
• Publication Date: 2017-02
• Subjects: Radiotherapy -- Xerostomia -- IMRT -- Head and neck -- Dose response -- QUANTEC; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2016.11.005
• Languages: English
• ISSNs: 0167-8140

Abstract

Abstract: Background and purpose: To study internal and external generalizability of temporal dose–response relationships for xerostomia after intensity-modulated radiotherapy (IMRT) for head and neck cancer, and to investigate potential amendments of the QUANTEC guidelines. Material and methods: Objective xerostomia was assessed in 121 patients (n Cohort1 = 55; n Cohort2 = 66) treated to 70 Gy@2 Gy in 2006–2015. Univariate and multivariate analyses (UVA, MVA with 1000 bootstrap populations) were conducted in Cohort1, and generalizability of the best-performing MVA model was investigated in Cohort2 (performance: AUC, p -values, and Hosmer–Lemeshow p -values (pHL )). Ultimately and for clinical guidance, minimum mean dose thresholds to the contralateral and the ipsilateral parotid glands (Dmeancontra, Dmeanipsi ) were estimated from the generated dose–response curves. Results: The observed xerostomia rate was 38%/47% (3 months) and 19%/23% (11–12 months) in Cohort1/Cohort2 . Risk of xerostomia at 3 months increased for higher Dmeancontra and Dmeanipsi ( Cohort1 : 0.17·Dmeancontra + 0.11·Dmeanipsi -8.13; AUC = 0.90 ± 0.05; p = 0.0002 ± 0.002; pHL = 0.22 ± 0.23; Cohort2 : AUC = 0.81; p < 0.0001; pHL = 0.27). The identified minimum Dmeancontra thresholds were lower than in the QUANTEC guidelines ( Cohort1/Cohort2: Dmeancontra = 12/19 Gy; Dmeancontra, Dmeanipsi = 16, 25/20, 26 Gy). Conclusions: Increased Dmeancontra and Dmeanipsi explain short-term xerostomia following IMRT. Our results also suggest decreasing Dmeancontra to below 20 Gy, while keeping Dmeanipsi to around 25 Gy. Long-term xerostomia was less frequent, and no dose–response relationship was established for this follow-up time.