Metabolic response as assessed by

backgroundStrategies to optimize management in rhabdomyosarcoma (RMS) include risk stratification to assign therapy aiming to minimize treatment morbidity yet improve outcomes. This analysis evaluated the relationship between complete metabolic response (CMR) as assessed by

methodsFDG-PET imaging characteristics, including assessment of CMR and maximum standard uptake values (SUVmax) of the primary tumor, were evaluated by central review. Institutional reports of SUVmax were used when SUVmax values could not be determined by central review. One hundred and thirty IR and 105 HR patients had FDG-PET scans submitted for central review or had SUVmax data available from institutional report at any time point. A Cox proportional hazards regression model was used to evaluate the relationship between these parameters and EFS.

resultsSUVmax at study entry did not correlate with EFS for IR (p = 0.32) or HR (p = 0.86) patients. Compared to patients who did not achieve a CMR, EFS was not superior for IR patients who achieved a CMR at weeks 4 (p = 0.66) or 15 (p = 0.46), nor for HR patients who achieved CMR at week 6 (p = 0.75) or 19 (p = 0.28). Change in SUVmax at week 4 (p = 0.21) or 15 (p = 0.91) for IR patients or at week 6 (p = 0.75) or 19 (p = 0.61) for HR patients did not correlate with EFS.

conclusionBased on these data, FDG-PET does not appear to predict EFS in IR or HR-RMS. It remains to be determined whether FDG-PET has a role in predicting survival outcomes in other RMS subpopulations.