Breast cancer is a common cancer among women worldwide. A variety of problems can occur during treatment, and persisting pain after surgery is one such issue. It can affect 20% to 50% of women after mastectomy (operation involving removal of breast) and is defined as pain in the chest, armpit, upper arm, and shoulder persisting for more than 3 months post-surgery. Treating this pain is important as persisting pain besides causing suffering, can negatively impact on mood, sleep, activities of daily living, social interactions, and overall quality of life. Reduced working ability and financial implications are obvious consequences as shown in one study where 54% of individuals reported reducing their workload to part-time as a direct result of pain. As the survivorship is increasing, enabled by the technological advancements in medicine, the focus needs to be equally on quality of life and reducing suffering. Phantom breast sensation (where one feels that the removed breast is still present) has an even higher incidence (60-80% of patients). The actual problem and pain may be underreported due to reasons such as worries about cancer reoccurrence, barriers in discussing personal issues, fear of being misconstrued etc.
Another subgroup of patients undergoing mastectomy are those who want to reduce their risk of developing breast cancer such as those with gene mutations (e.g., BRCA1, BRCA2) and a strong family history. Advances in surgical treatment like breast-conserving approaches have enabled patients to realistically consider this option.
Some factors associated with increased risk of persisting pain include:
Type of surgery: Nerve preservation approaches are associated with reduced incidence of sensory deficits (53 % vs. 84 %) but may not be possible in all cases.
Different breast cancer surgery options include
Axillary nodes dissection leads to increased chances of lymphedema (arm swelling due to inadequate drainage) and poses risks to one of the nerves (intercostobrachial nerve) which is responsible for the sensation of the inner aspect of the upper arm. Both of these factors can become a source of persisting pain. The wide variation in the size, location, and branching patterns of the nerve make it more vulnerable to injury. Damage may occur as a result of stretching during surgery or direct nerve injury, presenting with numbness and pain in the area supplied by the nerve. As per one study women with axillary node dissection are 3.1 times more likely to experience moderate-to-severe pain at rest.
Other nerves in the area are also at risk of injury and can become a source of persisting pain. These include
Other treatments like radiation therapy administered in conjunction with surgery increase risk of persisting pain. This may be due to increased tissue fibrosis, neural entrapment, and impaired shoulder movement. Moreover, radiotherapy also increases risk for lymphedema which is another reason for persisting pain. Later-stage disease also is likely to require more aggressive treatment (i.e., chemotherapy) and may be associated with higher rates of pain. Regardless these are necessary treatments and when indicated should be pursued.
Pre-existing pain prior to surgery is one of the most consistent factors related to increased risk of persisting pain after surgery. Even those patients with unrelated pain conditions such as headaches or low back pain are more likely to develop chronic pain after surgery.
Severe pain after the operation requiring high doses of painkillers increases the likelihood of persisting pain.
Age: In several studies, younger age was seen to be associated with greater likelihood of persistent pain. Although the exact reason is not known, some postulated factors include presence of more aggressive cancers requiring more aggressive treatment, higher preoperative anxiety, and the need for adjuvant chemotherapy in this group.
Psychosocial distress can be both a risk factor for and a consequence of chronic pain. Preoperative anxiety has been found to be related with immediate postoperative pain levels. Numerous studies have found correlations between persisting pain after surgery and depression, stress, and psychological vulnerability.
Postmastectomy pain syndrome may cause persistent or intermittent burning, shooting, stabbing, pulling, tightness, heaviness sensation or aching pain in
Other symptoms in addition to pain may include
Pain may persist after surgery due to numerous reasons such as surgical injury- nerve or muscle damage, nerve entrapment, lymphedema, mechanical causes, radiotherapy and chemotherapy, post-surgical scarring, recurrence of tumour, etc. Nerve injury pain has been further divided into the following types
Phantom pain is seen after amputations where the absent body part (phantom) hurts. The patient may experience sensation as if the removed breast is still present and is painful. Often patients are confused and reluctant in sharing this with others as they feel unsure if this is actually real and possible, but phantom pain is real and not just in one’s head. Controlling this can be challenging and requires a multi-modality (using many treatment options in combination) approach.
Nerve injuries can lead to the formation of neuromas which in simple language can be explained as swelling at the end of the injured nerve. These neuromas can generate spontaneous or provoked tingling, electric shock like sensation with increased sensitivity in the area. Neuroma pain may be more common following lumpectomy than mastectomy. I have come across a few cases where the patient experienced pain as if she was having a heart attack requiring multiple visits to hospital emergency whilst the actual problem was injured pectoral nerves and the pain responded to nerve blocks.
These patients present with persisting pain and sensory abnormalities following surgery. It is more common after operations involving the upper outer portion of the breast or the underarm area. Pain may be felt in axilla, inner side of upper arm, chest wall, shoulder or the surgical scar. Intercostobrachial nerve damage which can occur with axillary node dissection is considered as a common cause.
Mastectomy patients are also at increased risk for pain in the shoulder and/or scapulothoracic area (upper back and back of shoulder area). In one study approximately 27% of patients reported such problems even after 6 months of surgery and the possible causes can include
Reduced movements and guarding can lead to further decline in function, reduced lymphatic drainage and increase in pain.
There is paucity of good quality evidence regarding the long-term outcomes in post mastectomy pain with some studies suggesting reduction in chronic pain /sensation abnormalities whereas others reporting long term persisting pain in a significant proportion of patients. Persisting pain after surgery can be multifactorial and hence besides pain management, addressing psychosocial and functional disruption, using a multimodal approach, is equally important. Some of the options used in the treatment include
Medications: These may include different classes of medications such as special types of painkillers used for nerve pain called anti neuropathic medications. These include the anticonvulsants and antidepressants which are well known painkillers.
Before starting painkillers, an assessment to identify the likely pain generators is carried out and the therapy is tailored accordingly. Sometimes even the side effects of medications are utilised to our advantage like the sedative side effect to improve sleep. There are numerous other painkillers which can be utilised like opioids, anti-inflammatory agents, topical agents (e.g. capsaicin), numbing patches, painkiller patches, oral tablets, pain relieving nasal sprays and lollipops etc.
Physical therapy. Early initiation of physical therapy with gradual increase from range of motion exercises to active stretching, followed by strengthening is recommended. The aim is to preserve glenohumeral and scapulothoracic movement, strength, and to minimise arm dysfunction. Early initiation of physical therapy is supported by research evidence demonstrating better range of motion at 2 years post axillary node dissection surgery.
Another subgroup that can benefit from early therapy is those experiencing pain secondary to lymphedema. Apart from physical therapy other interventions such as occupational therapy, compression garments, manual lymph drainage, lymph-reducing exercises, skin care and weight loss may also be required.
Psychological treatments these may include options such as cognitive behavioural therapy (CBT), hypnosis, mindfulness-based therapies, meditation, self-management programs (individual vs. group) etc. Self-management programs focus on education, cognitive restructuring to modify thought processes and reduce distress, coping skills training (e.g., pacing, communication) and relaxation training (e.g., hypnosis, mindfulness).
Interventions/ Injections– these are discussed in the next section
The most appropriate intervention is decided keeping in mind the likely pain generator. Some of the options include
Trigger point injections Muscles ability to contract and relax plays an important role in body functioning. When muscles fail to relax, they form knots or tight bands known as trigger points. Common causes include inflammation, injury of the muscle or the neighbouring structures. Injection of local anaesthetic and steroid at the points of maximal tenderness can relieve chronic post mastectomy pain. The local anaesthetic blocks the pain sensations and the steroids help in reducing the inflammation, swelling. I prefer to perform these injections under ultrasound guidance as it improves the accuracy and reduces the chances of complications. Post injection physiotherapy is essential to prevent recurrence and maximise the benefits.
Nerve Blocks & Pulsed Radiofrequency – Intercostal, Pectoral Nerves
Intercostal nerves run in between two ribs to supply the chest wall. They carry messages from the chest wall to the brain and vice versa. Indications for intercostal block can be diagnostic or therapeutic. The procedure involves injecting a mixture of local anaesthetic and a small amount of steroid under ultrasound guidance. Using ultrasound helps to visualise the spread of drugs and reduce the chances of complications as the needle can be kept away from important structures such as lungs. Pulsed radiofrequency treatment can be performed to prolong the effects of the injections.
Cryoablation of Nerves The primary aim in cryoablation is deactivation of the nerves transmitting the pain signals and this is achieved by freezing the nerves in a controlled fashion to temperatures as low as minus 80 degrees. The procedure is performed using a special probe called cryoprobe, which is guided to the correct location using ultrasound, x-rays and nerve stimulators. The extremely low temperatures achieved at the tip of the cryoprobe results in formation of an ice ball which freezes the nearby nerves thereby reducing pain. This technology is a minimally invasive pain-relieving alternative that does not require any cuts or incisions. It is a safe, day care procedure with the potential of providing quick and lasting relief.
Plane Blocks – Ultrasound guided Serratus Plane Block (SPB) & PECS Block
These injections are commonly used during anaesthesia for breast surgery and can sometimes be useful in chronic pain situations. They involve injection of local anaesthetics and steroids, using ultrasound guidance, in specific planes between the muscles ensuring blockage of multiple nerves with a single injection. Serratus plane block can also block the intercostobrachial nerve, which is implicated in chronic post-mastectomy pain. In chronic pain conditions they are often used to break the pain cycle enabling patients to start physiotherapy.
Botox injections can help in situations where muscles are the source of pain and their spasm is an issue. They can also be useful when muscle pain is produced by the temporary expander as a part of the breast reconstruction. They work by temporarily paralysing the muscles thereby producing relief. Injections are best performed under ultrasound guidance to ensure accuracy and may need to be repeated after a few months if the problem persists.
Pulsed radiofrequency (PRF) of dorsal root ganglion (DRG)
DRG can be looked at as the modulator of the pain signals being transmitted from the periphery to the brain. By performing a block and pulsed radiofrequency procedure the pain impulses reaching the brain can be modulated/ reduced and this can produce pain relief. PRF of the DRG is considered for patients with inadequate response to other treatments discussed previously.
Stellate Ganglion Block this can be helpful in some cases in reducing pain and improving range of shoulder movements. These injections target special nerves called the sympathetic nerves, that can get involved in transmitting the pain signals to the brain. Sometimes a series of injections may be required to produce lasting relief.