Will the brain cancer in my client [name withheld] be cured by the Protocol session we performed on him or does he need to have a subconscious channeling session as well?

As you saw intuitively, he will benefit most completely having a subconscious channeling session for him. You indeed have been shown the proximal cause of the current struggle, and this can be nullified through healing and forgiveness, especially of the self at this point in time. It was his act of rage-filled hatred that registered on the karmic record and demands the repayment, in order for him to have health and wellbeing once again.