In a phase III study of quizartinib in the r/r setting, the results showed a superior overall survival (OS) of 6.2 months compared to 4.7 months (p < 0.0001). What does this outcome indicate?
a) Quizartinib is not effective in the treatment of r/r setting.
b) Quizartinib is equally effective as other treatments in the r/r setting.
c) Quizartinib shows superior efficacy in improving OS in the r/r setting.
d) Quizartinib has no significant impact on OS in the r/r setting.