The trifecta: great concept, lousy statistic

Abstract

The prostate cancer trifecta neatly encapsulates the idea that radical prostatectomy outcomes are multidimensional and competing. What we want for our patients is not just cure of cancer but recovery of urinary and erectile function; attempts to improve cure rates, by wider resection, can compromise functional recovery just as minimizing the risk of impotence or incontinence, by a more conservative resection, may increase the risk of recurrence.The problem with the trifecta comes when it is used as a statistic, with authors calculating a specifi c trifecta rate. Despite its intuitive appeal, the trifecta is a poor measure of radical prostatectomy outcomes. There are several reasons why the trifecta should not be used as an endpoint in prostate cancer research. These are discussed below. THE TRIFECTA IS STATISTICALLY INVALIDRecurrence and functional recovery occur over time; in statistical terms, they are ' time-to-event ' variables. There are two different types of time-to-event variable, failure and incidence, and it is not straightforward to combine them; yet this is exactly what is required by a trifecta analysis. A patient who recovers erectile and urinary function at 1 year, but recurs at 2 years, would be non-trifecta at 6 months, then go into trifecta at 12 months but then lose trifecta at 24 months. Exacerbating this problem is the fact that patients can lose and regain function repeatedly over time. For example, if we were to use a score of 24 on the International Index of Erectile Function-6 as the criterion for potency, one patient might have consecutive scores of 22, 25, 26, 23, 24, 23; if the patient were continent and recurrence-free, these scores would translate as non-trifecta, trifecta, trifecta, non-trifecta, trifecta, non-trifecta. By contrast, once a patient has recurred he is always considered to have recurred. So the trifecta mixes incidence and failure variables, with the former but not the latter being reversible. THE TRIFECTA IS MEANT TO INCLUDE THREE ENDPOINTS, BUT IS DRIVEN PREDOMINATELY BY ERECTILE OUTCOMESMore men recover urinary as compared with erectile function. In particular, whilst most patients who experience persistent incontinence are also impotent ( ∼ 90% in an informal analysis of data from the Memorial Sloan-Kettering Cancer Center), only a small proportion of patients who regain erectile function report pad use ( ∼ 10%). As a result, urinary outcomes have little effect on trifecta rates. It can also be shown that recurrence also has a smaller effect on trifecta than erectile dysfunction because it is less common. As a simple illustration, imagine that surgeon A has a long-term potency rate of 40% with 90% cancer control; surgeon B has slightly better potency (50%) but much poorer rates of cancer control (72%). Although these are very different outcomes, trifecta rates are identical: 40% × 90% = 50% × 72% = 36%. THE TRIFECTA IS OVERLY INFLUENCED BY SHORT-TERM OUTCOMESRecovery of urinary and erectile function typically occurs in the fi rst year or two after surgery; recurr...

Longitudinal evaluation of the frequency of sexual intercourse and sexual activity in patients after nerve‐sparing robot‐assisted laparoscopic radical prostatectomy

“…Sexual function (SF) after radical prostatectomy (RP) is one of the major problems affecting the quality of life (QOL) of patients with localised prostate cancer (PCa). In the era of robot-assisted laparoscopic RP (RARP), a 'trifecta' outcome (cancer control, urinary continence, and SF) is considered to be the optimum goal [1,2]. Erectile dysfunction (ED) has a significant impact on health-related QOL.…”