How to regenerate routes cache when the configuration changes in Symfony 2

Option 1
If your custom loader class can gain access to the kernel or the container (via DI), you could call the console cache clear command from that class.

E.g.

namespace AppBundle\MyLoader;

use Symfony\Bundle\FrameworkBundle\Console\Application;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\Console\Input\ArrayInput;
use Symfony\Component\Console\Output\BufferedOutput;
use Symfony\Component\HttpFoundation\Response;

class MyLoader
{

    private $kernel;

    public function __construct($kernel)
    {
        $this->kernel = $kernel;
    }

    public function myFunction()
    {
        $application = new Application($this->kernel);
        $application->setAutoExit(false);

        $input = new ArrayInput(array(
           'command' => 'cache:clear',
           '--env' => 'prod',
        ));
        // You can use NullOutput() if you don't need the output
        $output = new BufferedOutput();
        $application->run($input, $output);

        // return the output, don't use if you used NullOutput()
        $content = $output->fetch();

        // return new Response(""), if you used NullOutput()
        return new Response($content);
    }
}

Ref: Call a Command from a Controller
Disclaimer before someone points it out; Injection the kernel/conatiner is not considered "best pratice", but can be a solution.

Option 2
You could also write you own console command that extends Symfony\Bundle\FrameworkBundle\Command\ContainerAwareCommand that just calls the clear cache command.
Ref ; Call Command from Another

Option 3
This answer also gives you another option