MR Spectroscopy (MRS) Can Detect Very Early Responses to Chemotherapy

          Choline is an index of cell proliferation thus can be used as an early marker for treatment response. MR spectroscopy can be used to measure choline peak, and provide an early response marker that precedes tumor shrinkage. In the case example, the tumor size is decreased from 4.0 to 3.2 cm (20%), while the choline concentration is decreased from 2.36 to 0.75 mmol/kg (68%). Overall, the tumor that has a greater decrease in choline measured by MRS is more likely to achieve pathologic complete response.