Exact Sciences Corp., of Madison, Wis., has inked a deal to acquire Redwood City, Calif.-based Genomic Health Inc., creating a combined cancer diagnostics company with an estimated revenue of $1.6 billion by the end of 2020. The acquisition brings together Exact Sciences' at-home stool DNA test for colorectal cancer, Cologuard, and Genomic Health's Oncotype Dx tests for breast and prostate cancer. The three areas comprise about 40% of all solid tumor cases, according to the companies.