To our knowledge, this is the first population-based study of chronic pain after surgery for breast cancer that includes a comparable reference group.
The prevalence of PMPS in this study was found to be 24% as compared with PMPS-like symptoms in 10% of the reference group. The odds ratio for developing PMPS after treatment for breast cancer was 2.9. This prevalence for PMPS in women after surgery for breast cancer is similar to results obtained by Smith et al in (1999)
(29%) and Carpenter et al in (1998)
In one study, the prevalence has been found to be higher in low volume units than in high volume units (Tasmuth et al, 1999
). The prevalence of PMPS-like symptoms in women who had not had surgery for breast cancer is surprisingly high and mandates a conservative view on the raw prevalence figures.
The surgical procedures used in the region in the period 2003–2008 have remained principally unchanged. Mammographic screening had been introduced 10 years earlier and thus resulted in an increase in the number of women who could have breast-conserving procedures. The sentinel node technique became more widely used in the last part of the period and this has led to an increase in axillary-sparing procedures.
Three risk factors for developing PMPS were identified in this study: having undergone breast surgery earlier, tumour located in the upper lateral quarter and young age. Earlier surgery in the same breast appears to be a logical risk factor for PMPS. Regarding the location of the tumour, previous studies have not evaluated this variable as a risk factor. With tumours in close relation to the axilla, there is a higher risk of damaging nerves in the area that may increase the risk of subsequent chronic pain. Young age has also been reported to be a predisposing factor to PMPS in other studies (Tasmuth et al, 1995
; Smith et al, 1999
; Poleshuck et al, 2006
). It has previously been suggested that this may be caused by the more aggressive character of disease in this group of patients, requiring more invasive surgical procedures and chemotherapy (Kroman et al, 2000
; Colleoni et al, 2002
). However, in this study, these factors are included in the multiple regression analysis, and this indicates that other factors may account for the fact that PMPS is seen more often among young patients.
Two possible risk factors, which have been considered previously, are the sectioning of the intercostobrachial nerve (Abdullah et al, 1998
; Torresan et al, 2003
) and axillary dissection (Vecht, 1990
; Maunsell et al, 1993
; Hack et al, 1999
; Kakuda et al, 1999
; Johansen et al, 2000
). However, one study has shown the opposite result, with postmastectomy pain occurring without damage to the intercostobrachial nerve and in women without axillary dissection (Carpenter et al, 1999
). In this study, it was not possible to obtain information about the sectioning or preservation of the intercostobrachial nerve among the patients included. Axillary dissection came out as a risk factor in univariate analysis, but this effect could not be reproduced in the multivariate analysis.
We did not find any significant difference in the description of pain between breast cancer patients and the reference group. However, the location of the pain did differ between the two groups, with the majority of the breast cancer patients having pain in the shoulder, in the area of the scar and in more than one location. These findings are in agreement with earlier findings (Stevens et al, 1995
; Carpenter et al, 1998
). When using logistic regression analysis, we found that pain located in the mamma was seen approximately four times less frequent in the group of women who had undergone lumpectomy compared with the women who had undergone mastectomy. Sentinel node biopsy and axillary dissection was not associated with a significant effect on this pain location. Neither the type of breast surgery nor the type of axillary intervention had a significant impact on the frequency of pain located in the mamma. A similar pattern was observed for radiation therapy. An increase in pain located in the breast and especially pain located in the shoulder and arm was seen, when the radiation field included supraclavicular glands and the axillary region. A recent study, including 278 breast cancer patients, has addressed the impact of different types of pain on the degree of disability and distress (Kudel et al, 2007
). Three types of pain were studied: phantom breast pain, scar pain and other mastectomy-related pain. In this study, ‘other mastectomy-related pain' was found to be the strongest predictor of disability and distress. Demographic and surgical factors were not consistent predictors of pain or function.
For this type of study, some methodological limitations must be considered. The study group consisted of women who had undergone treatment for breast cancer at one centre, a teaching hospital, and all the women in the study group were Caucasian, that is, we do not know if the figures can be generalised to other settings. Further, it is possible that the percentage of women who did not have PMPS or PMPS-like symptoms was higher in the group of non-responders than in the group of responders. As the response rates in the study group and in the control group were 85 and 73%, respectively, the prevalence of PMPS and the odds ratio for developing PMPS may have been overestimated. There are no specific questionnaires for identifying and evaluating pain after surgery in breast cancer patients, and the questionnaires developed for estimating neuropathic pain components (Bennett, 2001
; Krause and Backonja, 2003
; Bouhassira et al, 2005
; Freynhagen et al, 2006
; Portenoy, 2006
) were considered not to be suited for the present purpose. Thus, we chose to make a questionnaire specifically for this study and we have no data to support its validity. Women with possible reoccurrence of cancer were included in the study and this is a potential bias of the results. The tumour itself may have caused pain and may thus have caused a higher prevalence of pain in the breast cancer group. Finally, our study comprised 219 patients, and the analysis of the risk factors may have been hampered by the low number of patients.
Chronic pain after surgery has been reported to develop in 5–60% of patients after operations such as thoracotomy, hip arthroplasty, hysterectomy, thoracotomy and inguinal hernia repair (Perttunen et al, 1999
; Aasvang and Kehlet, 2005
; Nikolajsen et al, 2006
; Maguire et al, 2006
; Pluijms et al, 2006
; Kehlet et al, 2006
; Brandsborg et al, 2007
). For hysterectomy, it was found that about 14% had pelvic pain more than 2 days a week and risk factors were preoperative pelvic pain, pain as the main indicator for surgery and pain problems elsewhere (Brandsborg et al, 2007
). Pain after total hip arthroplasty, which limited daily living to a moderate to very severe degree, occurred with a frequency of about 12%, and the risk factors were intensity of early postoperative pain and pain complaints from other areas of the body (Nikolajsen et al, 2006
). Prevalence of post-thoracotomy pain was observed to be 21%, when evaluated 6–7 years after surgery, and risk factors were age, consultant and time since surgery (Maguire et al, 2006
Only 22% of the breast cancer patients reported that the pain had an impact on the daily life and use of analgesics was low. These findings suggest that the severity of PMPS, in general, is moderate, which is in agreement with earlier studies (de Vries et al, 1994
). The majority of the breast cancer patients with severe pain have pain located in the shoulder, axilla or arm. This adds evidence to the finding of tumour located in the upper lateral quarter being an important risk factor, as operation in this area may tend to cause more nerve damage than surgery in other areas of the breast. This finding has not been reported in earlier studies.
In conclusion, it seems that, although recent advances in the diagnostic and surgical procedures have reduced the frequency of the more invasive surgical procedures, there is still a considerable risk of developing PMPS after treatment for breast cancer, and development of preventive measures as well as treatments of the syndrome are highly relevant.