Controlled trials are considered essential for proving a drug works better than other treatments or placebo. Controlled trials of Roche Holding's melanoma drug PLX4032, however, have added to the debate about whether controlled trials are ethical for evaluating cancer drugs that target genomic mutations. "[With genetically targeted] drugs that have minimal side effects and dramatic response rates, where we understand the biology, I wonder, why do we have to be so rigorous?" asked the chairman of human oncology at Memorial Sloan-Kettering Cancer Center. "This could be one of those defining cases that says, 'Look, our system has to change.'"