Chronic pain after breast cancer surgery: how one in every three women might be spared

One in every three women undergoing a mastectomy could potentially be spared chronic post-operative pain if anesthesiologists used a regional anesthetic technique in combination with standard care, says Faraj Abdallah, an assistant professor in the department of anesthesia at the University of Toronto.

Standard care for mastectomies is a general anesthetic, whereby anesthesiologists use gas to keep the patient asleep and narcotics to control pain. Up to 60 per cent of women experience chronic pain three months after they’ve had the surgery and at least half of those suffer from this pain one year later.

“Sadly, the pain these women experience can be so severely debilitating that it may require treatment by a pain specialist and pain killers,” said Abdallah, who is also an anesthesiologist at St. Michael’s Hospital.

The regional anesthetic technique Abdallah added to standard care – called ultrasound-guided paravertebral blocks – is similar to a dental freeze. Trained anesthesiologists use a local anesthetic to freeze nerves in the breast area.

Paravertebral blocks allow excellent pain control immediately after surgery and help with long-term pain reduction, Abdallah said.

“Six months after breast cancer surgery, we found that women who received paravertebral blocks immediately before their mastectomies had more than 50 per cent lower risk of developing chronic pain compared to those who received standard care,” said Abdallah.

The study, published in the journal PAIN, showed that these nerve blocks most significantly reduced neuropathic pain, which is the most common form of chronic pain affecting women after mastectomies. Unlike the soreness and aching associated with conventional pain – which may also affect these patients – neuropathic pain also affects sensation.

“One patient will lose sensation and not be able to feel a pin prick, another will experience severe pain if the skin is even lightly touched and the next patient may feel constant tingling or pins and needles,” said Abdallah. “Grading pain on a scale of one to 10 fails to capture neuropathic pain symptoms and frequently leads to under-diagnosis.”

Because each patient may experience different neuropathic symptoms pain, Abdallah said clinicians needed a reliable tool to assess this pain in women after breast cancer surgery and to measure how effective their interventions are at preventing this pain.

In this same study, the researchers also showed that a pain assessment test called the DN-4 can be used by clinicians to reliably identify chronic neuropathic pain in women after breast cancer surgery.

The DN-4 combines interview questions with a physical assessment performed by a clinician. It tests the patient’s sensation in the four areas where post-mastectomy pain is likely to occur – the breast, the chest, the shoulder and the arm.

“Breast cancer survival rates have improved significantly with advances in diagnosis and management, but chronic pain management after breast cancer surgery has not kept pace,” said Abdallah. “Proving that the DN-4 is a reliable test for this patient group is important because it gives clinicians a diagnostic tool to identify this pain, monitor its progress and measure the success of treatment.”

Abdallah began this randomized controlled trial while at Women’s College Hospital. Since joining St. Michael’s Hospital, Abdallah has continued this research and incorporated the paravertebral block technique into his practice at the hospital.

Research was supported by a grant from the Ontario Ministry of Health and Long Term Care’s Alternate Funding Plan Innovation Fund.

Geoff Koehler is a writer with St, Michael's Hospital, a partner of the University of Toronto.