2820 - Patient-Reported Xerostomia in Men Treated with Prostate Stereotactic Body Radiation Therapy: Implications for Future Radionuclide Therapy

D. Kallam¹, K. Gaudian², L. Gudenkauf³, M. J. Koh², R. Collins², Z. Zwart², M. Danner⁴, A. Zwart⁴, M. J. Ayoob⁴, D. Kumar⁵, M. Fallick⁶, G. Esposito⁷, S. Suy⁴, B. D. Gonzalez⁸, and S. P. Collins⁴; ¹George Washington University School of Medicine and Health Sciences, Washington D.C., DC, ²Department of Radiation Medicine, Georgetown University Hospital, Washington D.C., DC, ³Department of Health Outcomes and Behavior, Moffitt Cancer Center, Tamps, FL, ⁴Department of Radiation Medicine, MedStar Georgetown University Hospital, Washington, DC, ⁵Biotechnology Research Institute, North Carolina Central University, Durham, NC, ⁶Novartis, US Medical Affairs, Oncology, East Hanover, NJ, ⁷Department of Nuclear Medicine, Medstar Georgetown University Hospital, Washington, DC, ⁸H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL

Purpose/Objective(s): Prostate cancer is primarily a disease of older men who may possess a high burden of comorbid illness. Recently developed radionuclide therapy (RNT) is rapidly becoming a standard treatment option for metastatic prostate cancer. The FACT-RNT is a validated questionnaire which specifically assesses the Health-Related Quality of Life (HRQOL) of patients receiving RNT. Stereotactic Body Radiation Therapy (SBRT) is increasingly utilized in the management of localized prostate cancer. The aim of this prospective study is to evaluate the burden of chronic toxicities, specifically xerostomia, in men treated with SBRT who may require RNT in the future. Materials/

Methods: A cross-sectional assessment of HRQOL after prostate SBRT was performed using the fifteen- item FACT-RNT questionnaire. The FACT-RNT assesses symptoms and toxicities across several domains, commonly impacted by RNT, including xerostomia. The responses to individual questions were grouped into three clinically relevant categories (“not at all”, “a little bit to somewhat”, “quite a bit to very much”). Standard error was calculated to a 95% confidence interval. The dataset was divided into those with and those without xerostomia to analyze demographic and clinical data. Demographic and clinical characteristics included in multivariate and univariate analysis include age, race, risk group, and prior androgen deprivation therapy (ADT). P values for the comparison between patients were calculated using the Wilcoxon rank square test and chi- square test for non-normally distributed continuous, and categorical variables, respectively. P- values based on Fisher’s exact test were calculated due to some small cell counts.
Results: The overall FACT-RNT response rate was 49.5% (296 of 598 consented patients). The median age of responders was 78 years, 76% of patients were white, and 69% were of intermediate risk disease. Patients completed prostate SBRT at a median of 6 years prior to questionnaire administration (0-13 years). In this cross-sectional analysis, we observed a high rate of xerostomia, which is commonly seen post-RNT. Specifically, 24% of respondents reported xerostomia severity to be “a little bit” to “somewhat,” and 5% reported it to be “quite a bit” to “very much.” When comparing patients who experience xerostomia to those who do not, there were no statistically significant differences between the two groups in any baseline clinical or demographic characteristics.
Conclusion: In this cross-sectional prospective study, toxicities associated with RNT, such as xerostomia, were observed in a notable percentage of elderly prostate cancer patients treated with prior SBRT. This underlines the importance of a baseline assessment for xerostomia prior to RNT, not only to evaluate pre-treatment risk for subsequent salivary glands dysfunction, but also to better differentiate baseline abnormalities of salivary gland function from RNT-related side effects.