As far as lemon peels having anti-cancer properties, I don't know, but I was very excited to hear on t.v. a week or so ago about about turmeric or cumin having serious anti-cancer properties! From what I understand, it attacks the cancer cells on 5 different levels, from the beginning stage to the end stage and 3 stages in between. You can generally get turmeric from WalMart on the vitamin isle. It is also as effective as ibuprofen in relieving pain, but with no side effects! I hope this helps.
Citrus peels of any type are high in antioxidents which scientists believe help contribute to protection against cancer but there's no guarantee it will stop cancer. Other things citrus peels contain help aid in lowering cholesteral and help contribute protection against diabetes. You do not have to freeze them in order to be able to grate them and you can freeze the gratings simply by placing them in zip lock bags with as much air removed as possible.
The fruit of citrus fruits must be specially prepared to freeze for the best results. Here's a link that will explain how (scroll down to Table 2 for instructions):
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