To block or not to block during breast cancer surgery: That is the question two experts debated at the 2016 International Symposium of Ultrasound for Regional Anesthesia.
“There is enough evidence of short- and long-term benefits with paravertebral block [PVB] to encourage this as standard practice,” said Faraj Abdallah, MD, assistant professor in the Department of Anesthesia at the University of Toronto, and staff anesthesiologist at St. Michael’s Hospital in Toronto.
In Favor of PVB
Dr. Abdallah said several regional anesthesia techniques are now being used during breast cancer surgery, including pectoralis 1, pectoralis 2 and serratus anterior approaches, but there is only adequate evidence to support use of PVB.
The most compelling argument for administering PVB during breast surgery is that it prolongs survival, Dr. Abdallah said, while conceding that there are insufficient data to definitively support this view. The association, he said, was initially laid out in a retrospective study including 50 breast cancer surgery patients who received PVB along with general anesthesia and 79 who received general anesthesia alone (Anesthesiology 2006;105:660-664).
Those findings showed 94% of PVB recipients were metastasis-free at both two and three years after surgery, compared with 82% and 77% of those given general anesthesia alone who were metastasis-free at the same time intervals.
“The retrospective evidence spawned a lot of interest, and there’s an ongoing prospective trial at Mayo Clinic trying to validate these findings, but at the moment the evidence is not convincing enough on its own to recommend a practice change,” Dr. Abdallah admitted.
However, Dr. Abdallah said there is strong evidence from a meta-analysis of 24 randomized controlled trials with a total of 1,822 patients that PVB reduces pain scores and opioid consumption, so patients have fewer opioid-related side effects (Pain Physician 2015;18:E757-E780).
“There’s enough evidence to say that PVB should be incorporated into the standard of care for breast cancer surgery because of the improvements in these short-term outcomes,” he asserted.
PVB also benefits the “quality of recovery,” a patient-based outcome measure, Dr. Abdallah said. A controlled trial in which he and his colleagues randomly assigned 64 women undergoing breast tumor resection to receive either PVB with general anesthesia or general anesthesia alone showed that patients who received a PVB were able to maintain a higher quality of recovery through four days postoperatively (Anesthesiology 2014;120:703-713).
“There’s a big role for PVB in improving patients’ postoperative quality of life, including their physical and emotional well-being and their ability to resume normal life activities quickly,” Dr. Abdallah said.
There also appear to be positive effects on long-term outcomes after breast cancer surgery with PVB, he said, pointing to results from seven randomized controlled trials that have examined whether PVBs can reduce the likelihood of persistent postoperative pain, which at least 55% of breast cancer survivors experience (Anesthesiology 2000;93:1123-1133).
“This pain is predominantly neuropathic in nature; it is disabling, and it disrupts function and causes a deterioration in the quality of life,” Dr. Abdallah explained.
While studies on PVB and breast cancer surgery are heterogeneous, “if we look at specific subgroups and rely on IASP [International Association for the Study of Pain] definitions of chronic pain, the conclusion is that PVB is protective against persistent post-mastectomy pain following breast cancer surgery,” he said.
“For these reasons, it is only reasonable to incorporate PVB into the care standard for breast cancer surgery,” Dr. Abdallah said.
Not So Fast …
Dr. Abdallah’s debating opponent, Ban Tsui, MD, MSc, director of clinical research and professor in the Department of Anesthesiology and Pain Medicine at the University of Alberta Hospital, in Edmonton, began by accepting the rationale behind the argument that regional anesthesia could reduce postoperative cancer recurrence and metastasis.
“Regional anesthesia can decrease the effects of cancer surgery–related stress, which include depression of T-cell and natural killer cells function, an increase in proangiogenic factors and acute inflammation,” Dr. Tsui said.
However, he said, findings supporting this link are weakened by study design limitations, and there are results that do not confirm the association. His own research, for example, examined the effect of epidural anesthesia on outcomes after prostatectomy—a hormone-driven cancer that he believes is comparable to breast cancer—and showed no difference in recurrence rates when regional anesthesia was added to general anesthesia (Can J Anaesth 2010;52:107-112). “And many additional studies since then have also shown no difference in the setting of breast cancer,” he noted.
Responding to Dr. Abdallah’s claims that there are reductions in postoperative pain when using a PVB, Dr. Tsui asserted that findings from one of the pivotal randomized trials that showed this association should be taken with a grain of salt.
The study, Dr. Tsui explained, compared thoracic PVB and propofol-based general anesthesia (total IV anesthesia [TIVA]) with inhalation-based general anesthesia and opioid analgesia (Can J Anaesth 2015;62:241-251). While it found the PVB regimen provided an “early clinical analgesia benefit” and the latter regimen did not, the comparison between the two regimens was unfair and akin to comparing “apples to oranges.”
“The two studied groups were not only different in using or not using PVB but were also different in their maintenance regimes,” Dr. Tsui argued.
Moreover, his own research also has shown no differences in opioid consumption, length of PACU stay, rates of nausea and vomiting, or degree of chronic pain when a sham block was compared with a PVB in addition to a multimodal analgesia regimen and TIVA after mastectomy, he said (2015 annual meeting of the American Society of Regional Anesthesia and Pain Medicine, abstract 378).
“A multimodal regimen is adequate for controlling post-op pain in breast cancer surgery patients,” Dr. Tsui stated.
The Costs and the Risks
Dr. Tsui said he believes many clinicians perceive PVB to be “safer than it actually is.” He pointed to data that indicate a complication rate of 2.6% to 5%, with hypotension (4.6%), vascular puncture (3.8%), pleural puncture (1.1%) and pneumothorax (0.5%) topping the list of adverse outcomes (Contin Educ Anaesth Crit Care Pain 2010;10:133-137).
“The bottom line is that regional anesthesia is great for some surgeries but does not need to be used for breast cancer surgery, which is not associated with a lot of postoperative pain,” Dr. Tsui said, and asked, “Why use a sledgehammer to crack a nut?”