Table 2. Summary table of the case reports and case series included in the review.
F: female; M: male; CT: computer tomography; DVT: deep vein thrombosis; MRI: magnetic resonance imaging; PET: positron emission tomography; LN: lymph node; NSAID: non-steroidal anti-inflammatory drug; IV: intravenous; T: thoracic vertebrae; L: lumbar vertebrae; SCS: spinal cord stimulator; NRS: numeric rating scale
| Reference | Age and Sex of Participant | Primary Cancer | Clinical Presentation | Imaging | Cause of MPS | Treatments for MPS | Treatment Response | Survival Time Following MPS Diagnosis | |
| De La Cruz et al., 2013 [23] | 48 F | Ovarian cancer | Left flank pain Left thigh pain and paresthesia | Not reported | Metastases to left psoas muscle via supraclavicular and retroperitoneal LN | (1) Morphine, methadone, hydromorphone, hypogastric nerve block, epidural steroid injection, percutaneous cordotomy | (1) Persistence of pain | Unknown (in hospice) | |
| (2) Hydromorphone | (2) No treatment response information provided | ||||||||
| (3) Surgical treatment, radiation therapy, chemotherapy, clinical trial participation | (3) Persistence of pain | ||||||||
| (4) Morphine, physical therapy, gabapentin | (4) Pain sufficiently treated, still had nociceptive/ neuropathic pain with increasing numbness of the anterior thigh and sharp episodic pain | ||||||||
| (5) Methadone, hydromorphone, hypogastric nerve block, radiation therapy, cordotomy | (5) Persistence of pain, opioid-induced neurotoxicity, light decrease in pain at rest with an escalation of pain with activity | ||||||||
| (6) Oxycodone, hydromorphone, escitalopram, olanzapine, counseling | (6) Pain well controlled, anxiety managed | ||||||||
| Kalangara and Singh, 2018 [24] | 68 M | Melanoma | Left leg pain and numbness Weak left leg flexion and knee extension Left leg edema Erythema and inflammation left groin | CT | Metastases to left psoas muscle via supraclavicular and retroperitoneal LN | (1) Hydrocodone, oxycodone, gabapentin, duloxetine | (1) Persistence of pain due to side effects | 11 months (after SCS placement) | |
| (2) Acetaminophen, fentanyl transdermal patch, hydromorphone, topical lidocaine 5% patches | (2) Persistence of pain | ||||||||
| (3) Lumbar sympathetic block targeted at L3, fentanyl patch | (3) Paid reduced by 50% for 24 hours | ||||||||
| (4) SCS trial targeted at T10 for 5 days, fentanyl patch | (4) 75% pain relief with return to normal activities, adequate paresthesia to painful areas in the left groin and anterior thigh | ||||||||
| (5) Permanent SCS implant at T10, fentanyl patch | (5) 85% pain relief, improved function, and increased activities; pain fairly controlled at 8 months with SCS | ||||||||
| Kim and Choi, 2022 [25] | 39 F | Cervical cancer | Left pelvic pain Left thigh pain Fixed flexion of left hip | MRI | Metastasis to left psoas muscle fascia via abdominal LNs | (1) Morphine sulfate, chemoradiation, oxycodone, NSAIDs | (1) Persistence of pain, unable to extend left hip or sleep | Unknown | |
| (2) Epidural steroid injection at L2/L3 level | (2) Persistence of pain | ||||||||
| (3) Psoas compartment block with ropivacaine | (3) Pain decreased from 8-9 NRS to 3-4 NRS, pain returned after one week aggravated by extension of the hip | ||||||||
| (4) Botulinum toxin injection to psoas muscle | (4) Pain decreased to NRS 3 in two weeks, able to perform full hip extension, sleep, and walk comfortably, pain relief continued for nine weeks | ||||||||
| Kim and Choi, 2022 [25] | 68 M | Hepatic cell carcinoma | Right inguinal thigh pain Right buttock pain Painful limitation of motion | MRI | Metastasis to right psoas and iliacus muscles | (1) L4 nerve root block, palliative radiotherapy to iliac bone, fentanyl patches | (1) Persistence of pain | Unknown | |
| (2) Psoas compartment block with ropivacaine | (2) Pain decreased for one week, and upon returning was aggravated by walking or hip extension | ||||||||
| (3) Botulinum Toxin Injection to iliacus and psoas muscle | (3) Improvement seen after 2 weeks, able to fully extend the right hip, walk independently, pain decreased to 3-4 NRS, relief persisted for 12 weeks | ||||||||
| Kong et al., 2021 [10] | 61 M | Prostate cancer | Left paraspinal lumbar pain Left knee paresthesia Increased urinary frequency | CT PET | Metastases to left psoas muscle | (1) Bicalutamide, lacosamide, dexamethasone | (1) No treatment response information provided | Alive (at the time of original publication) | |
| (2) Leuprolide, docetaxel, pegfilgrastim, lacosamide, dexamethasone | (2) PSA value improvement, partial improvement of psoas muscle involvement, additional enhancement of adjacent areas seen on imaging | ||||||||
| (3) Radiation therapy to L3-S1 region | (3) No treatment response information provided | ||||||||
| McKay et al., 2017 13] | 68 F | Sarcoma of uncertain classification | Low back pain radiating down to left leg Fixed flexion of left leg (+) reverse straight leg raise test | CT MRI PET | Metastasis to left psoas | (1) Radiotherapy to the abdominal and pelvic portion of psoas muscle and tumor mass | (1) Significant pain improvement with improved mobility and quality of life | Alive (3 years post-surgery) | |
| (2) L4 vertebrectomy, left psoas muscle resected from L3 to L5 with resection of the left obturator nerve, genitofemoral nerve, L4 spinal nerve, and L4 root of femoral nerve | (2) Weakness of knee and ipsilateral hip adductor, patient remained disease-free for 3 years after surgery | ||||||||
| Mollica et al., 2019 [16] | 60 F | Non-Small Cell Lung Cancer NSCLC | Lower back pain Left leg pain | CT Chest X-ray | Metastasis to left psoas muscle | (1) analgesics and opioids (morphine) | (1) Poor relief of pain due to recurrent breakthrough pain episodes | 30 days (after admission) | |
| (2) continuous IV morphine infusion via an elastomeric pump | (2) Mild pain control | ||||||||
| Ota et al., 2017 [26] | 45 M | Gastric cancer | Back pain | CT MRI | Metastasis to left psoas muscle via abdominal paraaortic LNs | (1) Oxycodone, acetaminophen | (1) Persistence of pain | 19 days (after completing radiotherapy) | |
| (2) Oxycodone, flunitrazepam | (2) Persistence of pain | ||||||||
| (3) Epidural catheter for levobupivacaine and lidocaine | (3) Pain decreased for over 10 minutes to obtain CT | ||||||||
| (4) Oxycodone, acetaminophen, epidural levobupivacaine, oxycodone for breakthrough pain, radiotherapy. Bolus lidocaine or levobupivacaine before radiotherapy. Removal of the epidural catheter on day 15; completion of radiotherapy on day 16. | (4) Pain decreased to 3/10 (NRS) on day 16, worse with recumbency and supine position | ||||||||
| Stevens and Gonet, 1990 [4] | 60 F | Bladder transitional cell carcinoma | Gait disorder Left leg pain radiating to groin Positive psoas test | CT | Metastasis to left psoas muscle via paraaortic LNs | (1) morphine, prednisolone, diclofenac, doxepin, oxycodone | (1) Pain effectively controlled, no pain with gait | 5 months | |
| (2) radiation therapy | (2) Pain-free with some recurrent lower extremity edema | ||||||||
| Stevens et al., 2010 [2] | 53 F | Squamous cell carcinoma of the uterine cervix | Right groin allodynia and hyperalgesia Lower abdominal wall pain Right thigh pain | CT PET | Metastasis to right psoas muscle via pelvic and paraaortic LN | (1) Chemotherapy, morphine, acetaminophen, dexamethasone, venlafaxine, clonazepam | (1) Initially adequate pain control, over the next 2 weeks pain and distress rapidly increased | 4 months (after MPS diagnosis) | |
| (2) Methadone, hydromorphone rescue; gabapentin, midazolam, baclofen titration | (2) Minimum sustainable pain relief with titration | ||||||||
| Takamatsu et al., 2018 [1] | 31 F | Squamous cell cervical cancer | Gait disorder Left lower back pain radiating to hip, thigh, and knee Painful flexion of left hip | MRI | Metastasis to left psoas muscle via bilateral paraaortic LN | (1) tramadol, loxoprofen | (1) Persistence of pain | 8 months (after symptom onset) | |
| (2) oxycodone, naproxen, acetaminophen, pregabalin | (2) Persistence of pain | ||||||||
| (3) oxycodone, naproxen, acetaminophen, pregabalin, betamethasone | (3) Persistence of pain | ||||||||
| (4) Intensity-modulated radiation therapy to psoas muscles | (4) Pain reduced gradually and recovered normal gait | ||||||||
| (5) Opioid unspecified regimen | (5) Pain well-controlled for 4 months after discharge | ||||||||
| Takamatsu et al., 2018 [1] | 63 F | Uterine endometrial serous adenocarcinoma | Gait disorder Right leg weakness, edema, burning sensation, and pain Fixed flexion of right hip | CT | Metastasis to right psoas muscle via right paraaortic LN | (1) Oxycodone, loxoprofen, and acetaminophen | (1) Unspecified response | 7 months (after symptom onset) | |
| (2) Oxycodone, pregabalin, olanzapine, betamethasone | (2) Persistence of pain | ||||||||
| (3) External beam radiotherapy to the lesion | (3) Pain improved, normal gait recovered, no MPS symptoms recurred | ||||||||
| Takamatsu et al., 2018 [1] | 50 F | Fallopian tube cancer | Left lower back pain radiating to the lower leg Fixed flexion of left hip Abdominal distension | CT | Metastasis to left psoas muscle via bilateral paraaortic LN | (1) oxycodone, naproxen, acetaminophen | (1) Persistence of pain with intolerable side effects of increased opioid use | Alive (at time of original publication) | |
| (2) fentanyl, naproxen, acetaminophen | (2) Worsening of pain | ||||||||
| (3) paclitaxel and carboplatin chemotherapy, phase 3 clinical trial with either placebo or investigational drug | (3) Tumor remission achieved, symptoms disappeared | ||||||||
| (4) Salvage chemotherapy with paclitaxel, carboplatin, bevacizumab | (4) Pain progressively subsided and patient had no disease symptoms | ||||||||
| Takase et al., 2015 [15] | 59 M | Prostate cancer | Painful gait Back pain Left abdominal pain Right thigh unable to extend Positive psoas test on the right side | CT PET | Metastasis to right iliopsoas muscle via right common iliac LN | (1) Fentanyl, morphine hydrochloride hydrate, dexamethasone | (1) Persistence of pain | 6 months (after methadone initiation) | |
| (2) Etodolac, fentanyl, morphine hydrochloride hydrate, dexamethasone | (2) Persistence of pain | ||||||||
| (3) Methadone | (3) Pain resolved, pt was able to extend thigh and walk | ||||||||
| Takase et al., 2015 [15] | 35 M | Urachal cancer | Painful gait Left leg pain radiating to groin Left leg edema Fixed flexion of left thigh Positive psoas test on the left side | CT | Metastasis to left iliopsoas muscle via left common iliac LN | (1) Tramadol hydrochloride | (1) Persistence of pain | Alive (undergoing chemotherapy at the time of original publication) | |
| (2) Oxycodone SR, pregabalin, loxoprofen sodium hydrate, oxycodone rescue | (2) Persistence of pain | ||||||||
| (3) Methadone, oxycodone rescue | (3) Symptoms improved, decreased pain with walking and laying on the bed | ||||||||
| (4) Radiation therapy, chemotherapy, and methadone | (4) Pain well-controlled | ||||||||
| Takase et al., 2015 [15] | 70 F | Cervical cancer | Gait disorder Left lower abdominal pain radiating to the left groin and thigh Left thigh unable to extend Positive psoas test on left side | CT PET | Metastasis to left iliopsoas muscle | (1) oxycodone SR, loxoprofen | (1) Persistence of pain | 2 months (after methadone treatment initiation) | |
| (2) oxycodone | (2) Persistence of pain | ||||||||
| (3) fentanyl | (3) Persistence of pain | ||||||||
| (4) methadone, physical therapy | (4) Pain improved both at rest and with motion, patient able to extend the thigh | ||||||||
| (5) methadone, loxoprofen | (5) Pain levels reduced | ||||||||
| Tsuchiyama et al., 2019 [17] | 58 F | Bladder cancer | Gait disorder Right leg pain Fixed flexion of hip bilaterally | CT | Metastases to bilateral iliopsoas and pelvis muscles via extraperitoneal LN | (1) Gemcitabine, Carboplatin, Warfarin | (1) 10% reduction in tumor size | 8 months (after symptom onset) | |
| (2) Additional systemic chemotherapy cycles | (2) Increase in tumor size, increase in DVT, increased bilateral hip joint contracture | ||||||||
| Sanuki et al., 2022 [27] | 49 F | Ovarian cancer | Fixed flexion of left hip | CT | Metastasis to bilateral iliopsoas muscle via surrounding enlarged LNs | (1) Hydromorphone | (1) Persistence of pain | Unknown | |
| (2) Diclofenac | (2) Persistence of pain | ||||||||
| (3) Loxoprofen sodium hydrate | (3) Persistence of pain | ||||||||
| (4) Radiation therapy to the left side | (4) Able to lie supine, pain on left side decreased while right side increased | ||||||||
| (5) Radiation therapy to right side | (5) Durable pain relief bilaterally | ||||||||
| Sanuki et al., 2022 [27] | 54 F | Uterine Cancer | Gait disorder Right leg edema Fixed flexion of right hip Low back pain Right thigh pain | CT | Metastasis to right iliopsoas muscle | (1) Hydromorphone | (1) Persistence of pain, 4 NRS | Unknown | |
| (2)Radiation therapy | (2) Pain immediately resolved and maintained for 17 months, 0 NRS | ||||||||
| Yamaguchi et al., 2017 [22] | 68 F | Squamous cell carcinoma of the skin | Left thigh pain, exacerbated with extension Gait disorder (+) left psoas stretch test | CT | Metastasis to left iliopsoas muscle via left common iliac LN | (1) Oral oxycodone, loxoprofen, pregabalin | (1) Persistence of pain, disturbed walking | 2 weeks (after discharge) | |
| (2) Oral to epidural catheter L3/L4 opioid administration, fentanyl, ropivacaine | (2) Pain with rest resolved, able to extend left hip, able to ambulate with an aid | ||||||||
| Yamaguchi et al., 2017 [22] | 61 F | Bladder cancer | Right back pain Right thigh pain (+) right psoas stretch test | CT | Metastasis to right psoas muscle via right retroperitoneal LN | (1) Acetaminophen, increased oral oxycodone dosage, diazepam, radiation therapy to retroperitoneal LN and right psoas muscle lesion | (1) Persistence of pain with extension of right hip and ambulating due to nausea and somnolence | 3 months (after transfer to palliative care unit) | |
| (2) Switch oral to intrathecal catheter L2/3 opioid admin, added morphine, bupivacaine | (2) Pain resolved, and normal gait recovered | ||||||||
| Yamaguchi et al., 2017 [22] | 39 F | Cervical cancer | Pain with right hip extension Fixed flexion of right hip (+) right psoas stretch test Right thigh hypoesthesia | CT | Invasion of right psoas muscle by cervical cancer lesion in pelvis | (1) IV morphine switched to oral oxycodone, other analgesics (celecoxib, acetaminophen, betamethasone, pregabalin), and increased dosage | (1) Persistence of pain, patient unable to remain in the supine position | 6 weeks (after epidural treatment initiation) | |
| (2) Switched from oral to epidural catheter L3/L4 opioid administration, fentanyl, ropivacaine | (2) Pain improved, and the patient able to lie in the supine position |