Johnson & Johnson ( JNJ) ASCO presentation: Phase III study of Zytiga in "pre-chemo" prostate cancer patients. What we already know: Zytiga significantly delayed tumor progression in prostate cancer patients who have not been treated with chemotherapy. Zytiga also helped these patients live longer, although the survival benefit was not statistically significant. Based on these positive results, independent data monitors stopped the study early. Key questions: What was the magnitude of benefit provided by Zytiga? In particular, what does the survival benefit trend look like and might it become statistically significant on longer follow up? Other notes: At this point, the Zytiga study is the biggest attention grabber at ASCO from a Wall Street perspective because the results have far-reaching impact not only on J&J but prostate cancer drug competitors Medivation ( MDVN) and Dendreon ( DNDN).