Breast Cancer and Chronic Pain

March 20, 2014

Successful treatment for breast cancer may leave ongoing issues overlooked, including chronic pain. Two new studies highlight the need to explore the issue carefully with survivors.

Breast cancer can be a devastating disease both physically and psychologically. Even if the disease is successfully treated, many problems may remain. As a result important issues including ongoing pain may be overlooked.

I have often been consulted on and have treated patients with pain related to a wide variety of cancers, but have only rarely seen patients treated for breast cancer. Furthermore, many of the breast cancer patients I have seen were not referred by their treating physicians but by family members or friends in a healthcare profession who were acquainted with me. Many of my colleagues in pain management also tell me they have had limited experience with patients with breast cancer.

I see three possible explanations for this: either breast cancer patients rarely experience pain after diagnosis and treatment; or, oncologists and surgeons who are treating these patients are much more knowledgeable about pain management than their colleagues who treat other forms of cancer because, as repeated studies have shown, most practitioners in the latter group have limited knowledge about treating pain; or, the treating physicians are failing to properly address the pain. I lean toward the last explanation.

Two new studies highlight how frequent a problem pain is among those with breast cancer and how essential it is to provide more effective pain management for them.

The first study evaluated pain in 860 patients with breast cancer a year after they had undergone either breast-conserving surgery or mastectomy with axillary surgery involving lymph node dissection or sentinel node biopsy.1 All the patients had undergone preoperative pain assessment and, in addition to their medical histories, had completed two instruments for evaluating depression and anxiety. The same data was collected 12 months after the surgery.

At the 12 month follow-up, 34% of patients had no pain, 50% had mild pain, and 16% had moderate or severe pain. The factors most predictive for the presence of pain were:

   o chronic preoperative pain

   o preoperative pain in the area upon which the surgery was performed

   o preoperative depression

   o axillary lymph node dissection

   o chemotherapy and radiation therapy


These factors are what would be expected. If someone had a chronic pain condition unrelated to breast cancer, it would not be a surprise that treating the cancer would have little effect on that condition. In fact, with the focus on the breast cancer, other non-life threatening painful conditions might take a back seat.

If a patient had pain at the surgical site prior to the surgery, it might indicate that even before the operation there was already some pre-existing physiologic process at work upon which treatment for the cancer might have limited impact. The surgery itself might also exacerbate the pain. Lymph node dissection, for example, can result in lymphedema which can be very painful. 

Chemotherapy and radiation therapy can each cause chronic pain that may be even more severe than that related to either the cancer itself or surgery. Both can lead to a variety of pain syndromes, most notably neuropathic pain that is a result of injury to or destruction of nerves and is among the most difficult types of pain to treat. It is worth noting that although many physicians believe that the opioid analgesics are always the optimal medications for the treatment of pain, other medications, particularly the anti-epileptics and the serotonin-norepinephrine reuptake inhibitors, are often much more effective for neuropathic pain.

Depression as a predictive factor for pain also makes sense as many studies have identified a high degree of comorbidity between chronic pain and depression. We also know that when both chronic pain and depression are present, they tend to be more severe than if either problem is present alone.

My only criticism of this aspect of the study its use of the Beck Depression Inventory (BDI) to assess depression. The BDI was standardized on a physically healthy population and inquires about several somatic problems including loss of energy, changes in sleep pattern, changes in appetite, and loss of interest in sex. Obviously, patients with cancer might have some or all of these so even if they were not depressed the BDI might indicate they were. Thus when it is administered to patients with physical illnesses, it is difficult to determine if it is really only assessing depression.

 The second study focused more specifically on joint and muscle pain or other discomfort among breast cancer patients.2 It compared 247 patients with breast cancer who had completed adjuvant treatment including radiation therapy, chemotherapy, and hormone therapy with 274 women without this illness. For the cancer patients, the median time from diagnosis was 28 months.

Sixty-two percent of the cancer patients reported current pain compared to 53% in the control group. For the cancer group, several medications appeared to be predictive for the presence of pain including treatment with tamoxifen, taxane, and aromatase inhibitors.

The result I found most important in this study was that quality of life (QOL), as measured by the Short Form-36, an instrument commonly used to assess this domain in patients with pain, was significantly worse among patients with cancer than the controls and in cancer patients with pain compared to those without pain.

The authors of the study highlight the importance of not only inquiring about pain but also about the impact it is having on a patient's QOL and psychological state. QOL and level of functioning are often far better indicators than the level of pain itself as to whether treatments for chronic pain are truly helping the patients.

The authors also observe that patients who are treated for cancer may not consider their ongoing discomfort as being “pain” but perhaps as muscle aches and joint pain. Pain related to breast cancer and its treatment can take a variety of forms. Therefore health care providers may need to ask several questions to determine whether the patient is having sensations that the clinician would subsume under the general heading of pain but that could go undetected if only the word “pain” is used in inquiry.

References:

1. Meretoja TJ, Leidenius MHK, Tasmuth T, et al. Pain at 12 months after surgery for breast cancer. JAMA. 2014;311:90-92

2. Fenlon D, Addington-Hall JM, O'Callaghan AC, et al. A survey of joint and muscle aches, pain, and stiffness comparing women with and without breast cancer. J Pain Symptom Manage. 2013;46:523-535