HUDSON — A potentially life-changing stem-cell appointment scheduled for their son in Germany has been canceled, leaving a Stafford County family searching for answers.The notification for Ken and Brenda Grabast of Hudson came in an email from Anne Clausen, patient advisor for the XCell-Center in Dusseldorf, Germany.“Unfortunately I have to give you a sad message,” Claussen wrote Thursday morning. “Due to a new development in German law, stem cell therapy is currently not possible to perform at the XCell-Center. Regretfully for this reason, we cannot offer a stem cell treatment.