Regional Anesthesia and Breast Cancer Recurrence

Surgery is the primary and most effective treatment of breast cancer, but residual disease in the form of scattered micrometastases and tumor cells are usually unavoidable. Whether minimal residual disease results in clinical metastases is a function of host defense and tumor survival and growth. At least three perioperative factors shift the balance toward progression of minimal residual disease:

1. Surgery per se depresses cell-mediated immunity, reduces concentrations of tumor-related anti-angiogenic factors (e.g., angiostatin and endostatin), increases concentrations of pro-angiogenic factors such as VEGF, and releases growth factors that promote local and distant growth of malignant tissue.
2. Anesthesia impairs numerous immune functions, including those of neutrophils, macrophages, dendritic cells, T-cell, and natural killer cells.
3. Opioid analgesics inhibit both cellular and humoral immune function in humans, increase angiogenesis, and promote breast tumor growth in rodents.

However, regional analgesia attenuates or prevents each of these adverse effects by largely preventing the neuroendocrine surgical stress response, eliminating or reducing the need for general anesthesia, and minimizing opioid requirement. Animal studies indicate that regional anesthesia and optimum postoperative analgesia independently reduce the metastatic burden in animals inoculated with breast adenocarcinoma cells following surgery. Preliminary data in cancer patients are also consistent: paravertebral analgesia for breast cancer surgery reduced risk of recurrence or metastasis approximately four-fold (95% CI of estimated hazard ratio is 0.71 - 0.06) during a 2.5 to 4-year follow-up period compared to opioid analgesia. The investigators will thus test the hypothesis that recurrence after breast cancer surgery is lower with regional anesthesia/analgesia than with general anesthesia and opioid analgesia.

In this multi-center trial, Stage 1-3 patients having mastectomies will be randomly assigned to thoracic epidural or paravertebral anesthesia/analgesia, or to general anesthesia and opioid analgesia. As with all time-to-event trials, interim and final analyses are based on the number of outcome events (recurrences in this case) rather than enrollment. The number of patients required is just an estimate and varies based on actual recurrence rates which in turn depend on patients' stage and grade, and ancillary treatments. There will be three evenly spaced interim analyses and a final analysis at 351 recurrences. Confirming our hypothesis will indicate that a minor modification to anesthetic management, one that can be implemented with little risk or cost, will reduce the risk of cancer recurrence - a complication that is often ultimately lethal.