Tratar el tema is like “dealing with the topic”. We can’t deal with this topic now. We can’t focus on it now. Tratar del tema is more like discussing it. The leaders will discuss the topic at the next conference.
i'm not sure. it feels like the opposite when i read the definitions https://www.rae.es/diccionario-estudiante/tratar (3 & 11). is there another source you know