The idea behind the continued monitoring is to ensure that the edited cells act as they should. That is, that their (now deactivated) PD-1 proteins no longer halt a cell's immune response and let cancer spread. "The hope is, without PD-1, the edited cells will attack and defeat the cancer," Nature wrote.

This might not be the silver bullet against cancer, though. Naiyer Rizvi from Columbia University's Medical Center posits that the gene editing process could encounter a roadblock because it's a complex procedure and isn't very scalable -- especially compared to other methods like using antibodies.

"Unless it shows a large gain in efficacy, it will be hard to justify moving forward," he said.