ABSTRACT
Cancer is undoubtedly one of our most serious human health problems, with there
being high mortality rates worldwide of more than seven million deaths per year (Wein-
stein, 1991). In 1999, in the United States alone, it was estimated that 1,221,800 persons
will have been diagnosed with invasive cancer, and an additional one million people
would also contract basal or squamous cancers of the skin. Over 1,500 persons per day (or
over 563,100 Americans) will have died in 1999 from various manifestations of cancer
(Landis et al., 1999). The relative five-year survival rate for cancer patients is about 56% in
the United States (Anonymous, 1997). Among those organ sites with exceptionally low
five-year survival rates are esophageal, lung, pancreatic, stomach (all at 2%), ovarian
(39%), and breast cancers (20%) (Anonymous, 1997). Thus, the prevention rather than the
treatment of cancer has become of increasing importance in recent years.
