I have tried many ways of eating and paleo is my choice for life.
In my book the wins with Paleo:
1) Avoid vegetable oils.
2) Take Vitamin D (common recomendation)
3) Keep your omega 6/3 ratio low.
4) Avoid added sugar and fructose as an additive.
5) Avoid Soy
6) Great protein sources
These all are great for your body. I am convinced that these things are critical in avoiding/fighting cancer.
For the vegetarian:
1) Vegetable consumption is a good idea in my book. (This is also consistent with Paleo lifestyle.)
Common issues I see (and they are avoidable in the vegetarian lifestyle.
1) Consumption of Soy. Very Bad.
2) Over consumption of carbs. (pastatarians)
Lack of really good Omega 3 source (Now possible through vegan compatible DHA supplements however most / a lot of vegetarians do not know/take them but should.)
The addition of eggs, pastured butter and whey could improve the vegetarian diet and in fact are consistent with some forms of the vegetarian diet.
The addition of Salmon would really help. However the DHA mentioned above helps.
For the meat part. One though is that cancer is less likely to happen with a healthy pancreas. The over consumption of protein leaves pancreatic enzymes depleted and hence no pancreatic enzymes left to ward off cancer which they do seem to be able to do.
For me a Paleo diet is the way I am going. I do limit Protein to 170g / day which is 1 gram per lean pound of body mass.