Sadly, both Michio Kushi's wife and one daughter have died of cancer. Being that they were Japanese, the healthiest and longest lived people in the world, this doesn't really speak well for the diet.
However, it does seem that macrobiotics, when taken with common sense, have been known to help cancer patients, some say to the extent of "curing" them. It's easy to find examples to prove everything and the contrary (and no one mentions the ones that have died of the various deficiencies that easily befall macrobiotics followers).
Follow your own instincts... and keep in touch with a trusted doctor!