The insurance industry won a major lobbying victory Monday as the federal Medicare agency scrapped a proposed cut to Medicare Advantage plans. The Health and Human Services Department announced Monday that it will not follow through on a proposed cut to Medicare Advantage plans, which are administered by private insurers. The change comes after a fierce lobbying campaign from the insurance industry, which ran TV ads protesting the cuts and organized a massive letter-writing campaign among members of Congress. The Medicare agency had initially proposed a 2.2 percent cut in Medicare Advantage payments. But on Monday the agency said it had scrapped that cut and would instead offer a 3 percent payment increase next year.