Paraneoplastic Syndromes

Sophie Schellhammer

Hypercalcemia of Malignancy

Background 

  • Caused by PTHrP production (~ 80% of cases), osteolytic lesions (~20% of cases), and/or rarely exogenous Vit D.
  • PTHrP: SCC, renal, breast, bladder, ovarian carcinomas.
  • Osteolytic metastases: multiple myeloma, solid tumors metastatic to bone (breast cancer most common).
  • Exogenous vit D: hodgkin lymphoma and non-hodgkin lymphona can cause increased production of 1,25-dihydroxyvitamin D.

Evaluation 

  • Correct [Ca2+] for hypoalbuminemia: [Ca2+] + 0.8 x (4.0 – patient’s albumin).
  • Send basic hyperCa+2 work-up: PTH, vit D, etc (see “Hypercalcemia” section), PTHrP.
  • PTHrP production: PTHrP will be elevated.
  • Osteolytic metastasis: should see bony mets on imaging.
  • Labs: PTH low, low to low-normal 1,25 hydroxyvitamin D, low to low normal PTHrP.

Management 

  • See “Hypercalcemia” section.

SIADH

Euvolemic hypotonic hyponatremia with urine sodium >20 and typically urine Osm >100.

Associated with: SCLC (most common), head/neck cancers.

See "Hyponatremia” section for additional information and management

Carcinoid Syndrome

Background

  • Episodic flushing, diarrhea due to secretion of serotonin and other vasoactive substances.
  • Due to neuroendocrine tumors arising in lung or GI tract.

Evaluation 

  • 24-hour urinary excretion of 5-HIAA: UR 5-HIAA (ARUP).
  • Imaging to identify tumor(s): CT C/A/P with contrast.

Management 

  • Initial: somatostatin analogue (SSA) such as octreotide and lanreotide (see UpToDate for dosing).
  • Antidiarrheals to slow transit.
  • Diarrhea refractory to SSA: Discuss with oncology about Telotristat Ethyl in combination with SSA.

Autoimmune Encephalitis, Encephalomyelitis, and Myelitis

Background 

  • Encephalopathy ± myelitis (limb ataxia, sensory deficits).
  • Associated with SCLC and checkpoint inhibitor therapy. Anti-NMDA encephalitis can be associated with ovarian teratomas.

Evaluation 

  • LP: make sure to order CSF oligoclonal bands and CSF IgG index.
  • “Paraneoplastic AutoAb Eval-MAYO” (add "CSF" to the front of the order name if for LP).
  • NMDA-R can be ordered as a standalone test.
  • CT head.
  • EEG if concern for subclinical seizures.

Management

  • Consult Neurology for possible immunosuppressive therapy (steroids, IVIG).

Lambert-Eaton Myasthenic Syndrome (LEMS)

Background 

  • Muscle weakness due to autoantibody against calcium channels resulting in ↓ ACh release.
  • Associated with SCLC (most common) & lymphoma.
  • See “Myasthenia Gravis (MG) and Lambert-Eaton Myasthenic Syndrome (LEMS).”
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