Although it is well known that citrus fruits have health benefits and there is research being carried on all the time into their use, there is NO proven evidence that they cure cancer or that they are stronger than chemo.
The Health Sciences Institute replid to this hoax by saying:
I find it sad that some people prey on the fears of others by sending this misleading information. If you receive such messages DO PLEASE take the time to investigate the validity of their claims and share them here to warn others....................scientific studies indicate compounds in citrus, including lemon, have real potential as anti-cancer agents. However, it is not yet clear exactly how effective citrus will ultimately prove to be in preventing or fighting against cancer in humans. Certainly, it is premature and inaccurate to claim that lemon is a "proven remedy against cancers of all types." Nor, at this point, can it be said that lemon is a viable alternative to traditional treatments such as chemotherapy. But lemon, like other kinds of citrus is likely to be a healthy addition to your diet and may even reduce the risk of cancer.