In the UK alone, 42,000 new patients are diagnosed with primary breast cancer each year and most undergo surgery, either mastectomy or breast conservation surgery with sentinel node sample or clearance. Chronic pain was initially reported in the 1970s as a rare consequence of breast cancer treatment.62 There are now many epi-demiological and clinical studies reporting the prevalence and characteristics of persistent pain which suggest that it occurs commonly, with subsequent impact upon quality of life. There are several types of pain suffered by women after breast surgery.9,63,64 Although prevalence varies by methodology used and timing of follow up,10 post-mastectomy pain is thought to affect up to half of women undergoing surgery up to one year after their surgery.12 Chronic pain is also common after breast reduction and augmentation operations.63,65 It is also important to recognize that pain is not the only symptom that may be bothersome for patients after breast surgery; swelling, tingling, numbness, and other symptoms are commonly reported.14,66,67
The cause of pain following breast surgery is complex and various etiologies have been postulated. Early theories mostly attributed the cause to peripheral nerve damage and traumatic neuroma. Although predominantly referred to as "postmastectomy pain syndrome'' in the past, it has been suggested that this term be changed to intercostobrachial neuralgia (ICN) to describe the neuropathic pain syndromes, regardless of operative procedure, whether radical mastectomy or lumpectomy with axillary clearance.12 Damage may occur to nerves during surgery, particularly to the intercostobrachial nerve which arises from the second and/or third thoracic intercostal nerve and crosses the axilla supplying sensation to the upper half of the arm and axillary region. The intercostobrachial nerve is often sacrificed to accomplish complete removal of axillary lymph nodes. It was reported that sacrifice of the intercostobrachial nerve led to persistent discomfort, resultant numbness, and para-esthesia and that the nerve should be preserved wherever possible.68 However, preservation may not be possible because of tumor spread or anatomical variations in its course. The situation is complicated because throughout the 1990s, studies of breast conservation surgery reported that chronic pain and abnormal sensations persisted even where the nerve was preserved.69 Carpenter et al.70 state,
"the generally accepted risk factor of damage to the intercostobrachial nerve is mostly anecdotal.'' Axillary hematoma has been reported as a possible and treatable cause of postmastectomy pain syndrome.71 Chronic pain and persistent upper arm symptoms have been reported after lumpectomy, sentinel node biopsy procedures, and also breast augmentation or reduction surgery.63,65 70 72, 73 As the surgical procedure is quite different in these procedures, and the intercostobrachial nerve may not be affected, clearly other factors in addition to nerve injury contribute to the development of pain. The risk factors for CPSP after breast surgery are examined in more detail in Chapter 31, Preventing chronic pain after surgery in the Acute Pain volume in this series.
A comprehensive review article proposed a classification system for postoperative neuropathic pain after breast cancer surgery.12 The authors described nociceptive chronic pain after surgery as that resulting from injury to ligament or muscle, and neuropathic pain as that initiated or caused by a primary lesion or dysfunction in the nervous system. They suggest classifying the neuropathic pain syndromes into four groups: (1) phantom breast pain, (2) intercostobrachial neuralgia, (3) neuroma pain, and (4) other nerve injury pain. Although comprehensive in that it included 17 primary studies, the review was unsystematic in methodology and failed to describe bibliographic databases or search strategy, or the criteria for study inclusion or exclusion. The timing of pain chronicity ranged from two to six months after breast surgery. The review presents prevalence rates by pain syndrome: phantom breast pain (13-44 percent), ICN (13-61 percent), and neuroma pain (23-49 percent).12 This is the first attempt at syndrome classification; however, it fails to account for variation or misclassification within patient samples from individual studies, particularly because most primary studies have used postal methodology rather than detailed clinical assessment. Many patients may have mixed pain syndromes and may be troubled by other symptoms, not usually described as painful.14,66,67 The need for clean distinctions between syndromes for research purposes is not reflected in the clinical reality. Many patients present at pain clinics with complex problems and many different symptoms, and the challenge is to develop valid and reliable data collection tools to improve upon accuracy of detection and classification of syndromes.
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