Bloque plano de Serratus (SPB) versus capsaïcine versus Botox-A para dolor neuropático crónico en el síndrome posterior a la mastectomía (SERCABOT)

Participants in this arm will receive an 8% capsaicin patch in a single treatment session in addition to a systemic treatment that has been ongoing for at least 4 weeks. If pain persists, the capsaicin patch application may be repeated at 12 weeks.

One or two capsaicin patch (8%) are applied for 60 minutes to the site of neuropathic pain, in day-hospital. An oral, antalgic pre-medication may be done with one of the following medications (alone or association): paracetamol 1g, nefopam 30 mg, tramadol 100 mg, morphine 10mg, oxycodone 5mg. Capsaicin will be administered in addition to a systemic treatment that has been ongoing for at least 4 weeks. If pain persists, the capsaicin patch application may be repeated at 12 weeks.

• Qutenza®

Participants in this arm will undergo a Serratus Plane Block (SPB), a local anesthetic injection administered by a trained anesthesiologist, in addition to a systemic treatment that has been ongoing for at least 4 weeks. The SPB can be repeated every two weeks up to a maximum of four sessions within the initial 8-week period if pain persists. A repeat treatment may be considered at 12 weeks if further pain control is needed. This intervention aims to provide extended pain relief for neuropathic pain in post-mastectomy patients

The Serratus Plane Block (SPB) is a nerve block performed by a trained anesthesiologist to provide localized pain relief. It involves the injection of a local anesthetic: Maximum 150 mg naropeine combined with 150 μg clonidine hydrochloride into the serratus anterior plane under ultrasound guidance. An anesthesiologist will perform the procedure in a post-interventional recovery room, with light sedation.The SBP will be carried out in addition to a systemic treatment that has been ongoing for at least 4 weeks. The SPB may be repeated every two weeks up to four times in the initial 8-week period, with an additional repeat at 12 weeks if pain control remains insufficient.

• SPB

This arm involves administration of Botulinum Toxin A (Botox-A) at the site of pain, in addition to a systemic treatment that has been ongoing for at least 4 weeks. If pain remains unresolved, the injection may be repeated at 12 weeks. Botox-A is used here as a local, long-lasting analgesic intervention aimed at reducing chronic neuropathic pain in patients post-mastectomy.

Botulinum Toxin A (Botox-A) is injected into the affected area, with a total of 300 units administered across up to 60 injection sites. An anesthesiologist will perform the procedure in a post-interventional recovery room, with light sedation. This intervention will be carried out in addition to a systemic treatment that has been ongoing for at least 4 weeks, and is aimed at providing prolonged pain relief for post-mastectomy neuropathic pain. Light sedation is provided, and injections may be repeated at 12 weeks if necessary.

• Bótox
• Botox-A

The primary outcome measure is pain assessed by self-evaluation using the Numerical Pain Scale (END) ranging from 0 (no pain) to 10 (worst pain imaginable) at rest, evaluated 8 weeks after treatment (or 9 weeks after randomization if treatment was not performed). The patient's self-assessment reflects individual treatment efficacy. In case of treatment interruption due to immediate intolerance or technical issues, the baseline END will be considered for the primary analysis.

Defined as a reduction in pain of 3 points or more on the Numerical Pain Scale (END) at 8 weeks, with failure indicated in other cases.

Change in pain levels as self-reported by the patient using the END at 1, 2, 4, 6, 8, and 24 weeks after treatment (and at 13, 14, 16, and 18 weeks if treatment is repeated at 12 weeks).

Change in neuropathic symptoms assessed via the Neuropathic Pain Symptom Inventory (NPSI) at 1, 2, 4, 6, 8, and 24 weeks after treatment (and at 13, 14, 16, and 18 weeks if treatment is repeated at 12 weeks).

Early failure of local analgesic treatment defined by failure to perform the procedure (due to intolerance or technical issues) or failure to control pain as evaluated at 7 and 14 days post-procedure.

Documentation of any change in systemic treatement or introduction of new analgesic treatments (e.g., antiepileptics, antidepressants, opioids), with dosages collected at 1, 2, 4, 6, 8, and 24 weeks after treatment (and at 13, 14, 16, and 18 weeks if treatment is repeated).

Monitoring of adverse events possibly related to the treatment (capsaicin, botulinum toxin type A, or SBP block) during and after the local procedure, graded according to NCI-CTCAE v5.0.

Assessment of anxiety and depression using the Hospital Anxiety and Depression Scale (HADS) at baseline, 8 weeks, and 24 weeks.

Evaluation of health-related quality of life using the SF12 scale at baseline, 8 weeks, and 24 weeks.

Self-assessment of change in condition from 1 (no change or worse) to 7 (considerable improvement) measured at 8 weeks and 24 weeks.