Simply drop a new function of some lines inside ProjectConfiguration.class.php

public function configureDoctrine(Doctrine_Manager $manager)
{
if (ini_get("apc.enabled")==1)
if (sfApplicationConfiguration::getEnvironment() != "dev")
$manager->setAttribute(Doctrine::ATTR_QUERY_CACHE, new Doctrine_Cache_Apc());
else apc_clear_cache("user");
}

Every result will be cached inside [...]