Tool guides lymph node surgery in Asian prostate cancer patients

Researchers from Korea have developed a nomogram that predicts which Asian men with prostate cancer are most at risk for lymph node (LN) invasion.

The team, led by Koon Ho Rha (Yonsei University College of Medicine, Seoul), says it could be used to guide the counseling of patients on their suitability for pelvic LN dissection (PLND) prior to radical prostatectomy.

The team used prospective data on 541 Asian men who underwent robot-assisted (da Vinci Surgical System) radical prostatectomy and pelvic LN dissection by a single surgeon between 2008 and 2011. Overall, 45 (8.3%) had LN invasion.

Patients with LN invasion differed significantly from those without with regard to prostate-specific antigen (PSA) level (mean 21.2 vs 10.1 ng/mL), clinical stage (T3: 44.4 vs 7.3%) and biopsy Gleason score (≥8: 68.9 vs 22.8%), and these factors were independently associated with LN invasion on multivariate analysis.

Combining these three factors produced a model with an area under the receiver operating characteristic curve of 0.88, and using a 4% probability for LN invasion as the cutoff for pursuing PLND, the nomogram had a sensitivity of 95.6%, a specificity of 65.3%, a positive predictive value of 20.0%, and a negative predictive value of 99.4%.

The team calculates that using this model would spare 50% of patients without LN invasion from undergoing unnecessary PLND with no increase in the number of patients with LN invasion going untreated.

Reporting in BJU International, the researchers explain that PLND has fallen from favor with surgeons since the advent of robotic radical prostatectomy, and in light of uncertainty over the therapeutic benefits.

“Nevertheless, it is necessary to evaluate the risk of LN metastases and it would be against the oncological principle to arbitrarily omit PLND,” they comment.

However, while previous predictive nomograms have been developed, these all used data from Western populations and therefore may not be applicable to Asian patients.

“Nomograms are most useful when patients closely resemble the population from which the nomogram was derived,” comment Rha and colleagues, noting that in studies of patients from countries including Korea, China, and Japan, patients appeared to more commonly present with high-grade disease than in studies of non-Asian patients.

“We think that the present model might have a better predictive accuracy than pre-existing Western models in Asian populations or even in Asian men in the West,” they conclude.

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