Keycode.Escape in loop?,key.Escape in a loop

The code here is for quiting from main menu. But it runs only once. I want to run it whenever i press the androids h/w back button. Here's the code: void Update () {

     if(Input.GetKeyDown(KeyCode.Escape))
     {
         if (!isQuit)
         {
             isQuit = true;
             QuitMenu.SetActive(true);
         }
         else
         {
             QuitMenu.SetActive(false);
         }
     }           
 },The code below runs only once, i want it to run whenever i press the androids h/w back buton.

Here's the code:

void Update () {
if(Input.GetKeyDown(KeyCode.Escape)) { if (!isQuit) { isQuit = true; QuitMenu.SetActive(true); } else { QuitMenu.SetActive(false); } }
}