In 2019, in the United States, 1,762,450 new cancer cases were estimated, equivalent to 4,800 cases per day (8). Cancer and its consequences cause multiple chronic diseases in surviving patients. One of them, chronic cancer pain, has been described with a prevalence of 20–60% in survivors. Despite the availability of effective treatments for pain, over 50% of cases cannot achieve adequate oncologic pain (9).
Pain is the most common symptom of malignant chest wall tumors. Metastasis to bone structures or peripheral tissues is the most common etiology (85%) (6). Other causes of cancer pain in the chest wall include those caused by the adverse effects of surgical treatment, radiotherapy, or chemotherapy (17%) (9).
Although 70–80% of chronic cancer pain can be treated with multimodal analgesic therapy, tolerance with its long-term use, the presence of adverse drug effects or lack of effectiveness, multidisciplinary management by pain specialists and palliative care, and the use of interventional techniques are necessary for proper pain control in these cases (6). Among the interventions described in the literature for the management of chronic pain at the chest wall are intercostal nerve block, intercostal nerve neurolysis, paravertebral block, or the use of intrathecal devices (10, 11).
Regional interfascial techniques have been increasingly used in the recent years, using different deep interfascial planes for the dissemination of local anesthetics to a greater extent, managing to block several interfascial nerves with a single puncture (12). This technique has become massive in the recent years because of its lower technical complexity, few complications, and good results in the management of acute and chronic pain.
Here, we presented two cases of chronic chest wall pain of oncological origin refractory to multimodal pharmacological analgesic management, wherein ESP chemical neurolysis was performed under ultrasound guidance and fluoroscopic confirmation. In 2016, the blockade of the spine erector plane was described by Forero et al. as an alternative treatment for neuropathic pain in the chest wall (7). Due to its easy technical application, low risk of complications, and analgesic and anesthetic effects in a large area of multiple thoracic dermatomes with a single puncture, this technique has become an alternative with potential utility for the control of acute, chronic, traumatic, and acute postoperative pain in cardiothoracic surgery, abdominal surgery, and orthopedic surgery (13).
According to studies on cadavers and using imaging techniques with tomography and nuclear magnetic resonance, the most probable mechanism of action is the spread of local anesthetic from the lower plane of the erector spinae muscle group to the dorsal branch of the nerve root, which explains its analgesic and anesthetic effect in the dorsal region, and diffusion to the anterior branch, intervertebral space, epidural space, and even the sympathetic paravertebral chain (14, 15).
The use of neurolytic agents through the interfascial plane makes use of this technical superiority through the neurolysis of nerves located in the interfascial planes. This technique has the advantage of achieving a greater extension of its effect due to its greater dissemination and, in turn, achieving an analgesic effect of greater duration by denervation of afferent nociceptive fibers. Additionally, an opioid-sparing saving effect on opioid consumption would be achieved by this mechanism, reducing the adverse effects of chronic opioid consumption among patients with chronic cancer pain (16).
In our case, the ultrasound guide was initially used for the location of the erector plane of the spine, and an iodinated contrast medium was subsequently injected to verify the dissemination of the injected volume by fluoroscopy and to observe if there was dissemination to the paravertebral or epidural space. Discarding dissemination to these sites, a single injection of flat phenol was administered via the spine erector fascia, without demonstration during the procedure or subsequent monitoring of complications in both cases.
The cases of the two patients reported had a clear indication to perform this interventional procedure because, despite the use of a high dose of opioids, they did not experience adequate pain control and were exposed to greater adverse effects.
Other intervention options in these cases could include the use of neuraxial opioids, employing an implantable intrathecal pump (17); however, because of the short life expectancy in both cases, this technique would not be the first choice. An interfascial neurolytic procedure was chosen, which is a minimally invasive and low-cost procedure and can be used to look for the afferent pathways of nociception in the chest wall.
There are potentially serious adverse effects derived from the use of chemical neurolysis at a neuraxial level using phenol or alcohol. These include paraplegia, autonomic dysfunction, bowel dysfunction, bladder dysfunction, or death (18, 19). The authors suggest caution in the indications. It is not recommended as a systematic procedure, reserving it only for cases refractory to conventional medical treatment (20). Candidates for this technique include patients with a short life expectancy and intractable pain despite conventional treatment, without response to other less invasive measures, including maximum doses of opioids by any route of administration or the presence of marked tolerance or serious adverse effects to the use of these medications in the long term (11).
Ultrasound guidance is a reliable method to avoid intravascular administration of the neurolytic agent and to add a fluoroscopic guide to identify dissemination to the interfascial plane and decrease the risk of its neuraxial administration. We decided to administer the injection of phenol in the transverse process of T5 because it is a point closer to the areas of pain afflicting our patients, providing adequate coverage area of neurolysis in order to improve its analgesic effect. In both cases, an improvement in pain severity measured with VAS was achieved above 50%, with a duration of analgesia > 4 weeks.
These cases illustrate a novel use of interfascial neurolysis in the erector spinae plane, using a hybrid technique (ultrasound and fluoroscopic guidance) for the treatment of chronic refractory oncological pain. However, we highlight the fact that it should not be a first-line procedure due to the balance of risk-benefit in its application; however, it has been a useful tool in our pain clinic in patients with oncological severe chronic pain that involves the chest wall.
We acknowledge that evidence of the usefulness of the ESP block in the context of the treatment of acute and chronic pain is still scarce, and randomized controlled studies are underway to clarify its effectiveness and usefulness in these cases. Our intention is to report these cases showing a potential tool that, in the future, could be considered within the protocols of intractable chronic pain management in the chest wall. Additional prospective studies with a larger number of patients are required to clarify their clinical utility and determine the risk-benefit balance.