Supposing that cancer has spread from an origin, is that secondary cancer treated differently ?

Excellent question!!: The metastatic cancer is named the same as the primary but as you hinted, the treatment may be somewhat different. Most (not all) of the times, if a cancer spreads it is considered incurable so the intensity of therapy and the balance of benefits vs. Side effects is different compared to treating the primary. This depends a lot on the situation, so maybe you can give us more info.