Techniques for determining optimal duration for treatment of disease include receiving an untreated series of measurements and a treated series of measurements. The untreated series indicates temporal progression of a physical property related to a disease while the disease is untreated. The treated series of measurements indicates temporal progression of the physical property of the disease while a particular treatment is administered. A series of effectiveness values is determined based on the untreated and treated series. Each effectiveness value indicates a ratio between an untreated and a treated rate of change of the physical property at a corresponding time. An elapsed time is determined from start of treatment to an earliest time when an effectiveness value reaches an extreme compared to adjacent effectiveness values. Duration for treatment is based on the elapsed time, and is especially useful for each cycle of dose dense regimes for treatments with toxic side effects.