Body Mass Index is Associated with Higher Lymph Node Counts During Retroperitoneal Lymph Node Dissection

Objective: To determine whether body mass index (BMI) is associated with lymph node counts in patients treated with a primary retroperitoneal lymph node dissection (RPLND). Lymph node counts are a proposed measure of quality assurance for numerous malignancies. Investigation of patient factors associated with lymph node counts are lacking.

Methods: Using the Memorial Sloan-Kettering Testis Cancer Database, we identified 255 patients treated with a primary RPLND for nonseminomatous germ cell tumors (NSGCT) from 1999-2008. The associations between BMI and node counts were evaluated using linear regression models in univariate and multivariable models adjusting for features reported to predict higher node counts (year of surgery, stage, and surgeon volume).

Results: Median BMI (IQR) was 26.1 (23.4-28.7) and median (IQR) total node count was 38 (27-53). Median total node count for patients with a BMI<25, 25 to 29, and ≥30 was 35, 42, and 44 nodes, respectively. In a univariate analysis, higher BMI was significantly associated with higher total node counts (coefficient 0.7 nodes for each 1-U increase in BMI; P=.026). Features associated with higher node count on multivariate analysis included high-volume surgeon (P=.047), pathologic stage (P=.017), more recent year of surgery (P<.001), and higher BMI (P=.009).

Conclusion: Our results suggest for the first time that BMI is independently associated with higher lymph node counts during a lymph node dissection. If confirmed by others, these results may be important when using lymph node counts as a surrogate for adequacy of a lymph node dissection.