Stage migration: the trend continues, with implications for treatment
Posted Sep 28 2008 5:40pm
A team at the Duke Prostate Center has just published data substantiating the continuing “stage migration” that has resulted from early detection of prostate cancer over the past 20 years. They go on to suggest that such stage migration may have future implications for therapy. “Stage migration” is a term used to describe the gradual and apparently continuing tendency for patients to be diagnosed with much earlier clinical and pathological stages of their disease than was historically the case (at least in the USA).
The Duke group evaluated trends in pathologic staging among patients from the Duke Prostate Cancer Outcome database by looking at the true frequency of unilateral prostate cancer (prostate cancer in just one or other of the two lobes or sides of the prostate but not both, i.e., pathological stages pT2a and pT2b).
They identified 3,676 men with available pathology who underwent radical prostatectomy (RP) for localized prostate cancer between 1988 and 2006, defining the frequency of unilateral cancers during the periods 1988-1995, 1996-2000, and 2001-2006. Based on the patients’ surgical pathology, they then evaluated trends in pathological stage, pathological (post-surgical) Gleason score, and the percent of tumor involvement (PTI), i.e., the percentage of the prostate that was affected by cancer. Their results can be summarized as follows:
The frequency of stage pT2a increased from 2.8 percent of men undergoing RP in 1988-1995 to 13.0 percent in the period 2001-2006 (P < 0.0005).
PTI shifted towards low volume disease, e.g. the number of patients with PTI ≤ 5 percent increased from 10 percent in 1988-1995 to 37 percent in 2001-2006 (P < 0.005).
Among all patients with pT2a disease in the period 1988-2006, the proportion of pT2a tumors increased from 10 percent in 1988-1995 to 69.4 percent in 2001-2006.
Over the three time periods, 65 percent of patients with pT2a had minimal disease (PTI ≤ 5 percent), 14 percent had small volume disease (PTI = 5.01-10.00 percent), and 59 percent had pathological Gleason scores ≤ 6.
The authors suggest that the increasing prevalence of unilateral pT2a/T2b prostate cancer characterizes a growing proportion of men recently electing RP. These tumors are associated with lower PTI, pathological Gleason score ≤ 7, and a better biochemical progression-free survival in the 2001-2006 era.
They go on to suggest that these low risk pathologic characteristics support the potential for unilateral focal therapy in carefully selected patients.