Contrary to some previous studies, the use of paravertebral block (PVB) is not associated with a reduced rate of cancer recurrence or improved survival after breast cancer surgery, new research suggests.
There are two major hypotheses on the possible connection between PVB and breast cancer recurrence, according to Juan P. Cata, MD, study author, and assistant professor of anesthesiology and perioperative medicine at the University of Texas MD Anderson Cancer Center, in Houston:
- PVB reduces a patient’s stress response during surgery, decreasing inflammation and catecholamines, which have been shown, biologically, to promote cancer growth.
- PVB reduces the use of intraoperative opioids, which have been found in some animal models to promote cancer growth.
Dr. Cata said the latter hypothesis is “very controversial and depends on the animal model.”
He noted that PVB is “not the standard in any hospital.” Dr. Cata estimated that 80% to 90% of women undergoing mastectomy at his institution will have a PVB, whereas patients at other hospitals might not receive this block.
Also, there is speculation that volatile anesthetics could affect the behavior of cancer cells. A study by Exadaktylos et al showed a lower rate of recurrence for a small cohort of patients given a propofol infusion instead of gas (Anesthesiology 2006;10 5:660-664). However, subsequent retrospective studies have contradicted these results.
Dr. Cata and his colleagues conducted a retrospective analysis of 792 women who had undergone breast cancer surgery under general volatile anesthesia with and without PVB to explore any connection with cancer recurrence or overall survival. The researchers developed two propensity score models to create a matched sample of patients based on important clinical covariates. The findings were presented at the 2016 World Congress of Anaesthesiologists (abstract PR485).
“No significant associations were found between the use of paravertebral block in combination with volatile anesthesia and recurrence-free or overall survival,” Dr. Cata said. “The use of propensity score models allowed us to balance observed study characteristics, but the findings remained inconclusive.”
Of the 792 women who had breast cancer surgery, 198 (25%) had a PVB. For the first propensity score model, 191 patients who had received a PVB were matched—based on age, body mass index, anesthesia duration, surgery type and hormone receptor status—with 191 patients who did not receive a PVB.
Patients who received a PVB had significantly lower opioid consumption (P<0.001). The researchers did not find a statistically significant increase in the risk for recurrence (hazard ratio [HR], 1.20; 95% CI, 0.64-2.24; P>0.05).
In the overall survival analysis, PVB showed a reduction in the risk for death (HR, 0.83; 95% CI, 0.38-1.83), but this finding was not statistically significant.
The second propensity score model included the same covariates of the first model plus opioid consumption. PVB showed a reduction in the risk for recurrence (HR, 0.86; 95% CI, 0.33-2.23), but this finding also was not statistically significant.
Although no association with lower cancer recurrence was found, Dr. Cata cited several reasons to perform a PVB, including improved pain control, decreased use of opioids, less reported nausea and longer duration of pain relief.
“There are numerous reasons other than treating cancer to perform this technique,” he said. “When appropriately done, it’s a very safe and effective block.”
Depending on the local anesthetic, a proper block might last 12 to 16 hours, with some patients claiming positive results up to three days, according to Dr. Cata.
“Hopefully, I’m wrong,” he said. “But as of today, the data do not support a decrease in cancer recurrence with a paravertebral block, although it’s possible we were underpowered to show an association.”