There are some complications of cancer that cause rapid deterioration. The reason why this happens to some people and not others is not well understood. One of

There are some complications of cancer that cause rapid deterioration. The reason why this happens to some people and not others is not well understood. One of the more common rapidly fatal complications is disseminated intravascular coagulation, where the cancer stimulates widespread blood clotting that consumes all the normal clotting factors and results in bleeding which can easily be fatal. It is perhaps not so well understood that a cancer is not 'part of the person'. Our notions of good health presuppose the concept of a united system of physiological functions. Cancer doesn't follow this rule. It is an invasive, foreign organism who's singular purpose is to keep growing no matter what. It is less sophisticated than a virus in that respect. Assessed on a genomic level, you may have less in common with your cancer than you do with your neighbor.