Study Type--Therapy (case series). Level of Evidence 4. What's known on the subject? And what does the study add? In lymph node dissections for cancer, the more extended the dissection, the higher the number of lymph nodes removed. In addition, the higher the number of nodes retrieved, the better the staging. This leads many investigators to set a threshold of a minimal number of nodes below which the dissection is considered inadequate. Although the minimal threshold concept is generally good, it is not based on very objective data. a number of factors might influence the final number of nodes removed: (i) the surgeon and the surgical technique; (ii) the pathologists and tissue processing technique; (iii) the patient; and (iv) the audit effect and feedback to the surgeons about the number of nodes removed.
Objective: • To examine the number of lymph nodes removed over time for men undergoing a standard pelvic lymph node dissection (PLND) during radical prostatectomy.
Patients and methods: • In total, 2119 consecutive patients with clinically localized prostate cancer were scheduled for non-salvage radical prostatectomy between February 2005 and September 2009. • All patients underwent PLND, including the external iliac, hypogastric and obturator fossa nodal groups. • We tested whether the number of lymph nodes increased over time by including the date of each patient's surgery into a linear regression model using nonlinear terms.
Results: • From 2008 onward, there appears to be a large increase in the number of nodes removed. • Date of surgery was a significant predictor of the number of nodes removed (P < 0.001). • The anatomical template of dissection, the specimen submission and pathological assessment were reportedly unchanged. • The nodal yield increase in the later part of the study coincides with an increase in the academic interest in PLND and nodal metastasis in prostate cancer at the institutional level and worldwide.
Conclusions: • Without any intentional change in surgical technique or pathological processing, the number of lymph nodes removed in our radical prostatectomy experience increased. • This change coincided with an increased academic interest in the subject and highlights the positive feedback effect. • The change also raises concerns about unaccounted for confounding factors that could affect multi-institutional datasets and surgical clinical trials.
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