If it cannot metastasize then it isn't cancer in the way a layperson thinks of that term.
Basal cell carcinoma, a cancer that unfortunately I've had a lot of experience with, never
metastasizes, yet it can eat through other tissue and even bone if left untreated. My dictionary uses the term "malignant" as a necessary part of the definition: "a malignant growth or tumor resulting from the division of abnormal cells," and, other than the obvious definition of malignant to mean harmful, it defines it as: "(of a tumor) tending to invade normal tissue or to recur after removal." So the question hinges on whether a true
GS6 is malignant.
TurpT1a, my understanding of the 2005 revision of the Gleason grading system was that it decreased
the risk associated with both
GS6 and GS7, via the "Will Rogers Effect." This occurred because the highest risk GS6s were moved into GS7, thereby lowering the risk of both categories. It's called the Will Rogers Effect because he said, perhaps apocryphally: "When the Okies left Oklahoma and moved to California, they raised the average intelligence level in both states."
But where is a 3+4 supposed to come from if it doesn't come from what used to be a 3+3?
It is not at all clear that cells "evolve" up the chain from grade 3->grade 4->grade 5. There may be a stem cell-like common ancestor that spawns higher grades as well as lower grades. So higher grades may evolve in parallel with
lower grades, rather than from
lower grades. One very small pilot study found: "These data support a model of parallel evolution of lower and higher Gleason score disease, rather than progression from Gleason 6 to higher Gleason scores." This is not settled science -- just a hypothesis for now about
the natural history of PC.The genomic relationship among matched prostate cancer foci.