TU‐A‐WAB‐04: A Prospective Longitudinal Study with Ultrasound Nakagami Imaging to Evaluate the Relationship Between Acute and Late Normal‐Tissue Toxicity in Breast‐Cancer Radiotherapy

Abstract

Purpose: Radiation‐induced normal‐tissue toxicity is heterogeneous in nature and manifests in a wide range of severities across women who undergo breast‐cancer radiotherapy (RT). Numerous studies have investigated the relationship between acute and late toxicity based on patient‐and physician‐conducted assessments, and the results have been conflicting. We carried out a prospective longitudinal study to examine whether acute toxicity can predict late toxicity in breast‐cancer RT using quantitative ultrasound Nakagami imaging. Methods: Twenty‐two patients were enrolled following lumpectomy and all participants received whole‐breast external‐beam RT (50Gy plus a 10Gy boost). Each participant received up to 6 ultrasound scans. A baseline ultrasound scan was performed 1 week prior to RT and followed by a scan at week 6 of RT. Four additional scans were taken post‐RT at 6‐week, 3‐month, 6‐month, and 1‐year follow‐ups. Patients were imaged on both breasts with a 10‐MHz ultrasound. Nakagami shape parameter was used as a surrogate for acute and late toxicity. A Nakagami shape parameter ratio (NSPR) was generated using measurements from the irradiated breast over the contralateral breast. Clinical assessment of normal‐tissue toxicity was conducted by a radiation oncologist using RTOG toxicity scheme. A linear regression model was used to examine the relationship between acute and late toxicity. Results: The NSRP measurements correlated with RTOG toxicity. For most patients, NSPR increased during RT and up to 3 months post RT, reached the highest value between 3 and 6 months, and then started to recover. The linearregression model indicates the NSPR during RT are correlated with NSPR measured at 3‐month, 6‐month and 1‐year post‐RT (p<0.05). Conclusion: Our results based on ultrasound Nakagami imaging suggest that acute normal‐tissue toxicity predicts late toxicity (up to 1 year) following breast RT. Therefore, interventions designed to limit acute toxicity may Result in less late toxicity and improved quality‐of‐life of breast‐cancer survivors.