It's hard to make these studies accurate if the participants aren't being monitored on their consumption.  It's possible that the test indicates that encouragement from a health professional to a patient isn't an effective way to ensure patients actually consume 7 servings of vegetables per day.  Also, if those same patients are consuming foods or doing activities that encourage cancer progression, it's difficult for a study to be accurate.  

Thanks for reporting on it.  I wish the study showed that simply encouraging patients to eat 7 servings of vegetables/day would result in patients doing it AND that doing so slowed or stopped PCa progression.  More studies are needed for sure.  Keep learning and fighting!