Malignant psoas syndrome is said to be extremely rare, but I keep seeing it. Admittedly, working in the pain and palliative care service in a specialist cancer centre, if anyone was going to see it, you would think it would be my team.
I have had three patients with MPS this year and because each time it’s something that the clinical staff are not familiar with, I thought I would share a short summary with the Palliverse.
The original description of MPS in 1990 (1) described patients with:
- Metastatic cancer involving the psoas major muscle either intrinsically (direct intramuscular metastasis), or extrinsically from metastatic retroperitoneal lymph- adenopathy infiltrating into the muscle.
- Painful flexion of the ipsilateral hip with positive psoas stretch test (‘‘reverse’’ straight leg raise) related to psoas muscle spasm or irritation.
- Clinical evidence of proximal (L1–L4) lumbar plexopathy with spontaneous, burning and lancinating pain associated with hyperalgesia (allodynia and hyperesthesia).
- Absence of osseous lumbar vertebral metastases and/or concomitant lumbar polyradiculopathy due to other causes (e.g., malignant neuraxial dissemination, chemotherapy-associated or radiation-induced neurotoxicity).
In 2010, Stevens et al wrote a helpful review (2) of MPS with a case review, mechanisms and theories. Five years ago, according to the paper, there had only been 28 cases reported in the English speaking literature.
I will leave interested readers to explore the papers themselves, but it describes polymodal pharmacotherapy (aka throw everything at it), plus some novel strategies like local anaesthetic block of psoas sheath.
What has encouraged me to put fingers to keyboards tonight though is the referral of yet another patient with psoas syndrome, plus this Japanese case series by Takase et al (3). It describes three patients with MPS who had excellent results with methadone (15-30 mg/day). Their average pain scores were reduced by an astounding 7 points with greatly improved function.
I am pretty keen to try adjuvant methadone for my new referral.
Have you seen any malignant psoas syndrome cases before?Were they recognised and treated as such? How did it go? Particularly keen to hear whether anyone has tried methadone.
1. Stevens MJ, Gonet YM: Malignant psoas syndrome: Recognition of an oncologic entity. Australas Radiol 1990; 34:150–154.
2. Mark John Stevens, Charlotte Atkinson, and Andrew M. Broadbent. Journal of Palliative Medicine. February 2010, 13(2): 211-216. doi:10.1089/jpm.2009.0193.
3. Takase Naoto, Ikegaki Junichi, Nishimura Harumi, Yuasa Sayoko, Ito Yumiko, and Kizawa Yoshiyuki. Journal of Palliative Medicine. July 2015, 18(7): 645-652. doi:10.1089/jpm.2014.0387.