Choice of Nephron Sparing Technique correlates with change in GFR: Percutaneous Radiofrequency Ablation (RFA) vs. Open and Laparoscopic Partial Nephrectomy.
Ali K. Daha, M.B.B.S., Audley L. Osbourne, M.D., Christopher J. Cutie, M.D., Debra A. Gervais, M.D., Douglas M. Dahl, M.D., Adam S. Feldman, M.D..
Massachusetts General Hospital, Boston, MA, USA.
Background: In appropriate cases nephron sparing techniques are employed for the management of Renal Cell Carcinoma (RCC). Partial nephrectomy has been demonstrated to preserve long term renal function as compared to radical nephrectomy. We compare three nephron sparing techniques: radiofrequency ablation (RFA), open partial nephrectomy (OPN), and laparoscopic partial nephrectomy (LPN) in an effort to determine if these methods differentially affect glomerular filtration rate (GFR).
Methods: Under IRB approval, we performed a retrospective analysis of all patients who underwent RFA, OPN, and LPN from November 1998 to June 2007. We began performing LPN in January, 2002. We evaluated gender, age, comorbidities by charlson score, relevant past medical history, tumor size on preoperative imaging, preoperative GFR, and GFR at 6-12 months post procedure. Statistical methods included t-test/ANOVA or Wilcoxon/Kruskal-Wallis for continuous data and chi square or Fisher’s Exact for categorical data. The GFR was calculated using the MDRD Clinical GFR calculator by using the patient’s serum creatinine levels, age, sex and race.
Results: A total of 311 patients were treated with RFA, 118 with LPN and 162 with OPN. 121 RFA patients, 73 OPN and 40 LPN patients had follow-up serum Cr at 6-12 months post-procedure available in their records. Absence of follow-up creatinine in the record was not associated with procedure choice or other clinical variable. The mean preoperative GFRs for RFA and the partial nephrectomy groups were 65.28 (SE 2.08) and 67.07 (SE 2.16), respectively, demonstrating similar preoperative renal function (p=0.55). The mean change in GFR at 6-12 months post-procedure was 9.57 (SE 1.28) for the RFA group, and 4.16 (SE 1.33) for the partial nephrectomy group. This was statistically significant (p=0.0039). Within the entire partial nephrectomy cohort, the mean change in GFR was 2.82 (SE 1.65) in OPN and 6.62 (SE 2.23) in LPN. This difference was not statistically significant (p=0.1726).
By multivariate analysis using a linear regression model, which controlled for age, tumor size, presence of hypertension and/or diabetes, the greater change in GFR was seen in those who underwent RFA compared to those who underwent partial nephrectomy.
Conclusions: Our series suggests that RFA may be associated with a worsened preservation of renal function compared with partial nephrectomy. Although not statistically significant, we also found that the decrease in GFR in OPN was slightly less than LPN. We are further investigating this potential difference to evaluate warm ischemic time and other operative variables.