Evaluating the Association between Body Mass Indices and the 21-Gene Recurrence Score: A Systematic Review and Network Meta-Analysis.

Background: Preconceptions exist regarding the association between obesity and the propensity to develop estrogen receptor positive (ER+) cancer. There is limited data assessing the impact of body mass index (BMI) on 21-gene recurrence score (RS) results.

Aim: To perform a systematic review and network meta-analysis to assess whether increased BMI is associated with low RS in estrogen receptor positive (ER+) breast cancer.

Methods: A systematic review was performed as per PRISMA guidelines. Descriptive statistics were used as appropriate. Meta-analyses were performed using the Review Manager v5.4 and NMA performed using shiny.

Results: 6 studies with 3523 patients were included. The mean age was 61 years and mean RS was 16.6 and BMI was 25.8 When applying traditional RS cut-offs 66.4% of patients had a RS < 18 (3529 out of 5312), 27.6% had RS 18-30 (1466 out of 5412) and 6.0% had a RS of > 30 (317 out of 5312). At meta-analysis, patients with RS 18-30 (risk ratio (RR): 1.15, 95% confidence interval (CI), 0.91-1.46) and RS > 30 (RR: 1.03 95% CI, 0.79-1.35) were not associated with lower BMI. When applying TAILORx cut-offs, 24.2% of patients had a RS < 11 (996 out of 4124), 63.1% had a RS 11-25 (2604 out of 4124) and 12.7% had a RS > 25 (524 out of 4124). At meta-analysis, patients with RS 11-25 (RR: 1.57, 95% CI, 0.77-3.75) and RS > 25 (RR: 1.58, 95% CI, 0.71-3.77) were also not associated with lower BMI.

Conclusion: This study failed to identify a significant association between BMI and RS group.