Survival analysis of patients with breast cancer undergoing a modified radical mastectomy with or without a thoracic paravertebral block: A 5-year follow-up of a randomized controlled trial

Abstract

Aim: This 5-year prospective follow-up of women randomized to general anesthesia (GA) with or without a thoracic paravertebral block (TPVB) examined the risk of local recurrence, metastasis and mortality after breast cancer surgery. Patients and Methods: A total of 180 patients undergoing modified radical mastectomy were randomized to one of three study groups: standardized GA only; GA with a single-injection TPVB (s-TPVB) and placebo paravertebral infusion after surgery for 72-h; and GA plus with continuous TPVB (c-TPVB) for 72-h postoperatively. Cox proportional models were used to assess the effect of TPVB on long-term outcomes. Equivalence testing was used to help interpret the results. Results: The incidence [95% confidence interval (CI)] of cancer recurrence, metastatic spread and all-cause mortality was 2.3% (0.7-5.4%), 7.9% (4.6-12.6%) and 6.8% (3.6-11.2%), respectively. Four women had cancer recurrence and had metastatic spread. Compared to the GA-only group, the risk of metastatic spread was not different from that of GA with s-TPVB [hazard ratio (HR)=1.11, 95% CI=0.32-3.83) nor from that with GA plus c-TPVB (HR=0.79, 95% CI=0.21- 2.96) (p=0.88). Compared to the GA-only group, the risk of mortality was similarly not different from that of the two other groups (HR=2.57, 95% CI=0.66-9.92; and HR=0.66, 95% CI=0.11-3.97, respectively, p=0.15). Conclusion: Although the original study was underpowered to properly address long-term outcomes, the results of this analysis suggest that TPVB, administered whether as a single-injection or continuous infusion during the perioperative period, had little to no appreciable effect on local recurrence, metastasis or mortality after breast cancer surgery.