How should we specifically pray for John?

A friend of mine, (Lou Bailey) was praying for John the other night and sensed that as we pray, we need to pray specifically against multiplication of the exising cancer cells.

An enemy increases power by adding to its troops, so we need to pray that no cancer cell would divide any more (which obviously is what leads to tumours and further spreading of disease)...praying that the enemy would advance NO further.... because He couldn't because of the power of prayer.