Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_39_2504 - Diffusion-Weighted MRI As an Early Biomarker of Xerostomia in Oropharyngeal Cancer Patients Treated with Radiation Therapy

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Diffusion-Weighted MRI As an Early Biomarker of Xerostomia in Oropharyngeal Cancer Patients Treated with Radiation Therapy
B. Elgohari1,2, A. S. Mohamed1, S. P. Ng1, H. Elhalawani3, A. K. Elsayes4, R. He4, Y. Ding5, J. Wang5, M. Elawadi2, I. Awad2, K. A. Hutcheson1, G. B. Gunn1, S. J. Frank1, A. S. Garden1, D. I. Rosenthal1, S. Lai1, and C. D. Fuller6; 1The University of Texas MD Anderson Cancer Center, Houston, TX, 2Mansoura University, Mansoura, Egypt, 3Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, 4MD Anderson Cancer Center, Houston, TX, 5The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, TX, 6University of Texas Graduate School of Biomedical Sciences, Houston, TX

Purpose/Objective(s): Studies have shown demonstrable salivary glands diffusion-weighted (DW)-MRI changes between pre- and post-radiation (RT). We aim to determine whether the apparent diffusion coefficient (ADC), derived from (DW-MRI), can provide an early (mid-RT) non-invasive biomarkers of salivary glands injury and subsequent xerostomia.

Materials/Methods: Our institutional database was retrospectively reviewed for oropharyngeal cancer (OPC) patients treated with definitive radiotherapy and had available pre- and mid-RT DW-MRI acquired in the same radiation treatment position using proper immobilization devices, following an IRB approval. Salivary glands (ipsilateral parotid (iPA), ipsilateral submandibular (iSM), contralateral parotid (cPA), contralateral submandibular (cSM) and sublingual (SL)) were manually segmented using T2 weighted sequences at the two-time points. These contours were subsequently propagated to the corresponding DW-MRI and were checked for proper alignment with the corresponding region of interest using a commercial image registration software (Velocity AI v3.0.1). The ADC maps were generated and planning CT scans and dose grids at mid-RT were retrieved and co-registered to MRIs. Mean ADC values and mean doses were extracted. Statistical analysis was conducted using non-parametric Wilcoxon signed-rank and Spearman’s tests.

Results: A total of 30 OPC patients were included. The cohort median age (IQR) was 59 years (53-63). Male gender 88% and white race 88% predominated. Tonsil and base of tongue represented the site of tumor origin in 58% and 42%, respectively. All patients had stage III-IV disease and 97% were HPV positive. Twenty-six patients received IMRT and four patients received IMPT. The median prescription RT dose was 70 Gy in 33 fractions. The median dose (IQR) to iPA, iSM, cPA, cSM, SL at mid-RT were 20 (14-28), 37 (35-45), 13 (10-20), 33 (27-38), 27 (20-30) Gy, respectively. 47% of patients developed xerostomia G≥2 at 3-month post-RT. Our results showed a statistically significant increase in mean ADC values at mid-RT in all ROIs compared to baseline values (p<0.01 for all). The highest percentage of increase in ADC was noted in iPA with average 30% increase from baseline values. A weak correlation between dose and delta ADC was noted for iPA (Spearman ρ= 0.25, p=0.2). Patients with xerostomia G≥2 at 3-month had a significantly higher increase of mean ADC of iPA and iSM at mid-RT compared with patients with xerostomia G<2 (62% vs 15%, p=0.02 for iPA, and 31% vs 10%, p=0.04 for iSM). Using recursive partitioning analysis, an increase of ADC >71% in iPA was identified as the most significant predictor of xerostomia G≥2 (p<0.0001).

Conclusion: DW-MRI at mid-RT predicted radiation-induced salivary gland injury and subsequent xerostomia in OPC patients treated with radiotherapy and appears as a promising tool for adaptive RT applications after further validation of our results in future studies.

Author Disclosure: B. Elgohari: Research Grant; Joint supervision program. A.S. Mohamed: None. S. Ng: Employee; The University of Texas MD Anderson Cancer Center. H. Elhalawani: None. R. He: None. Y. Ding: None. J. Wang: Research Grant; Elekta. M. Elawadi: None. K.A. Hutcheson: None. G.B. Gunn: Associate Medical Director; MD Anderson Cancer Center - Proton Therapy. S.J. Frank: Research Grant; C4 Imaging, ELEKTA, U19. Founder and Director; C4 Imaging. Honoraria; ELEKTA, Varian Medican Systems, Inc. Advisory Board; Varian Medican Systems, Inc. Stock; C4 Imaging. Royalty; C4 Imaging. Patent/License Fees/Copyright; C4 Imaging. Chairman; American Brachytherapy Society. Director; C4 Imaging. Director-at-large; North America Skull Base Society. A.S. Garden: None. D.I. Rosenthal: Advisory Board; BMS. S. Lai: Research Grant; NIDCR Grant. C.D. Fuller: Research Grant; National Institutes of Health, National Science Foundation, Elekta AB. Grant funding; Elekta AB. Honoraria; Nederlandse Organisatie voor Wetenschappelijk Onde. Consultant; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Travel Expenses; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Reviewer; Radiological Society of North America. Associate Editor; Radiographics. Data Management Task Force Committee Member; MR-LinAc Consortium. Member; National Cancer Institute. Task Group Member; American Association of Physicists in Medicine.

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