Dr. Ruane wants to conduct a study on the incidence of breast cancer in people aged 50-70 in Baltimore over the next 15 years. He comes to you because he needs help with his study design. He only wants to include individuals who have never been diagnosed with any form of cancer. Which of the following study designs would be most appropriate for Dr. Ruane's study?
1) Case-control study
2) Cohort study
3) Cross-sectional study
4) Experimental study