1. Combinations of effective agents produce at least an additive increase in complete remission rates over that which can be achieved when the agents are used individually.
2. Patients who do not achieve complete remission with initial treatment have a significantly shorter survival.
3. Alternating MTX and 6-MP at 28-day intervals during remission does not prolong the duration of remission over that of combined concurrent 6-MP and MTX.
4. The administration of folic acid antagonists intrathecally at 28-day intervals during antimetabolite maintained remission did not prolong the duration of remission. Meningeal leukemia, however, occurred significantly less frequently in these patients.
5. The duration of combined 6-MP and MTX maintained remission is not greater than that of 6-MP maintained remission.
6. The toxicity of 6-MP and MTX in combination in patients in remission is additive.
The above conclusions were drawn from this comparative study of combinations of chemotherapeutic agents in children with acute lymphocytic leukemia.