A federal health panel has endorsed an experimental cancer test that uses a blood sample to detect multiple forms of the disease. The Wednesday vote from a panel of Food and Drug Administration advisers could pave the way for broader adoption and insurance coverage for the test from manufacturer Grail Inc. The positive decision came despite many lingering questions about the test’s potential downsides. Risks include that the test misses some common cancers while flagging cancer risks in people who are actually healthy. The panel vote is not binding and the FDA will make a final decision in coming months.