The dominant approach in cancer treatment is direct confrontation: identify the tumour, send a drug to fight it. One drug against one target on the battlefield of advanced disease. This paper proposes a structural alternative. If cancer is understood as a dissipative system that runs a cycle -- sixteen steps in a mandatory order, each producing the input for the next -- then every step contains a threshold that must be crossed for the tumour to advance. Each threshold is itself a four-step process. The mathematics of sequential gates shows that attacking a threshold at all four of its sub-steps blocks 99% ofcrossings, while attacking a single sub-step blocks only 70%. Reaching 99% with one drug would require 100-fold potency over the biological process. Reaching 99% with four drugs requires only 3-fold potency each. Four moderate drugs beat one miracle drug. This paper identifies thirty-six intervention points across nine actionable positions in the tumour lifecycle, names the molecular target at each, and maps the existing drug that addresses it. 89% of these drugs are approved or in clinical trials. The proposal is not to fight the tumour head-on with a single weapon, but to place four obstacles at each threshold the tumour must cross -- before it reaches the next stage. Not a battle. A series of barriers that make progression structurally impossible.