MP47-13: Muscle Mass Change Using Linear Measurement Analysis after Nephrectomy for pT3 Renal Cell Carcinoma is Associated with Mortality

Alexandra Medline*, Eric Midenberg, Dattatraya Patil, Sean Evans, Fatima Kamal, Kenneth Ogan, Atlanta, GA, Sarah Psutka, Seattle, WA, Mehmet Asim Bilen, Viraj Master, Atlanta, GA

Introduction: Preoperative skeletal muscle deficiency is an established risk factor for poor survival outcomes in patients with renal cell carcinoma (RCC). However, given the dynamic nature of skeletal muscle associated with malignancy, there is a need to evaluate the prognostic benefit of muscle area change from the pre- to postoperative period. We hypothesized that increasing muscle area following nephrectomy, measured by linear segmentation of L3 psoas and paraspinal musculature, is associated with improvement in overall survival (OS) and cancer specific survival (CSS) for patients with T3 RCC.

Methods: We retrospectively analyzed 125 pT3 RCC patients who underwent nephrectomy from March 2004 to February 2020 with available pre- and postoperative axial CT or MRI studies segmented at the L3 vertebrae. The majority were N0 (81%) and M0 (76%). Psoas and paraspinal muscles were measured bilaterally using a validated digital ruler tool. Total muscle area (TMA) was calculated by aggregating the area of all four muscles and total muscle area index (TMI) by dividing the TMA by height squared (m2). The prognostic value of postoperative muscle loss, defined as any decrease in muscle area index, was analyzed using Kaplan-Meier and Cox proportional stepwise hazard models.

Results: Median time between preoperative scans and surgery was 41 days and between surgery and postoperative scans was 199 days. Forty-two patients (33.6%) had an increase in total muscle area index post-nephrectomy (IQR=33.4; p= <.0001). On Kaplan-Meier analysis, postoperative decrease in TMI was associated with increased odds of mortality (p=0.0012; Figure 1) with a median follow-up of 37.4 months. In a multivariable Cox regression analysis, compared to those with improvement in TMI after nephrectomy, any reduction of TMI was associated with decreased OS (HR=4.69, 95% CI 2.21- 9.98, p<0.001) and decreased CSS (HR=5.90, 95% CI 2.13-16.31, p<0.001). A 10% or more reduction was also associated with decreased OS (HR=2.28, 95% CI 1.25-4.18, p=0.007).

Conclusions: Any decline in TMI between preoperative and initial postoperative imaging after nephrectomy was associated with decreased OS and CSS in patients with pT3 RCC. Perioperative linear segmentation is an efficient tool that may improve current prognostication methods and can be performed on any imaging software platform.

Source of Funding: Robinson & Churchill Family Foundation