Glucose monitoring device maker DexCom stock rallies more than 50% in October to pace the S&P 500

keep them on track to be the S&P 500’s SPX, -0.49% best October performer with a month-to-date gain of 50.6%. The rally comes as maker of glucose monitoring systems reported last week third-quarter results that beat expectations and got a boost from the Centers for Medicare and Medicaid Services’ issuing a proposal that would expand the coverage of glucose monitoring devices. Just behind DexCom on the S&P 500’s October best-performers list was cruise operator Norwegian Cruise Line Holdings Ltd.’s shares NCLH, +2.88% with a 49.7% rally this month, followed by oil services company Halliburton Co.’s stock HAL, +0.61% with a 47.4% gain. Year to date, the S&P 500’s best performer has been oil and gas producer Occidental Petroleum Corp.’s stock OXY, +1.22% by a wide margin, as it has rocketed 154.6% this year while fellow energy company Hess Corp.’s stock HES, +0.71% was second with a 92.9% advance.