Pelvic lymph node dissection and prostate cancer-specific survival after surgery
Posted Jan 19 2011 12:00am
According to an editorial commentary by Evans on the UroToday web site yesterday, a Canadian study published in BJU International last November has raised some interesting questions about the potential value of pelvic lymph node dissection (PLND) during the surgical treatment of men with prostate cancer of any stage.
Withrow et al. set out to investigate whether there was any association between the number of lymph nodes removed at pelvic lymphadenectomy in men undergoing a radical prostatectomy between 1990 and 1998 and the subsequent risk of prostate cancer-specific mortality. They focused, in particular, on patients with low- to intermediate-risk, supposedly localized prostate cancer.
They were able to show that there was a small, possible (but not statistically significant) increase in prostate cancer-specific survival resulting from lymph node removal in patients who were node negative, based on a particular analytical model.
In his editorial comments on this article, Evans notes that, “For every lymph node removed the risk of [prostate cancer-specific mortality] was reduced by 3%, although the data did not reach statistical significance.”
This is not the first time that someone has suggested that PLND may be of benefit even in patients with node-negative disease. Evans lays out three possible explanations for this apparent effect, effectively suggesting that:
An extended PLND is simply a surrogate for a really well-conducted surgical procedure.
Better pathology based on more lymph nodes is a surrogate for the improved outcome.
Pathologic understaging is a surrogate for the improved outcome.
The “New” Prostate Cancer InfoLink thinks there may be a quite different explanation, which is that in the 1990 to 1998 time frame, in Canada and elsewhere, many patients were still being diagnosed with locally advanced as opposed to truly localized forms of prostate cancer, and the ability to distinguish clinically and pathologically between men with truly localized and truly locally advanced disease was still limited. Given that fact, the results demonstrated by Withrow et al. may just reflect the inadequacy of the data on which the study was based, and have little at all to do with whether a PNLD was carried out or not.
It also needs to be recognized that carrying out a PNLD does add to the risk for complications from a radical prostatectomy even in skilled hands. We feel we would need to see some much more compelling data before it was suggested that extended PLND was to become a routine component of the majority of radical prostatectomies for patients with localized prostate cancer today. It seems unlikely to us that any prostate cancer-specific survival benefit is going to be large enough to overcome the added risk for such men.
It would be interesting to see if analysis of data from a larger database could replicate these results. However, it may continue to be difficult to understand exactly how to act on such data even if they were shown to be true.