Pectin is an amazing nutrient. One of the best sources is the white inner peel (pith) of citrus fruits - it's 30% pectin. Plus, the pith also contains cancer-fighting flavinoids, such as quercetin along with vitamin c and rutin, which conveniently assists in the uptake of vitamin c.
Loads of info about cancer, pectin and nutritional healing on my (basically neglected) blog.
See the lengthy (2-pages so far) thread reports of beating cancer in a week with ideas for eating alkaline foods, including fruits that are alkaline, and an interesting tidbit on lemon grass toward to bottom of page one. Lemon grass is an herb, not a fruit, I know, but when cancer is the topic, I figure it's worth a mention!