Radiation Oncology/Toxicity/Brachial Plexus

Brachial Plexus RT Tolerance

• Three distinct syndromes
  • Transient neuropathy
  • Classic, delayed, progressive fibrosis - unlikely to occur <60 Gy
  • Acute ischemic plexopathy

• Dose constraints
  • RTOG 0236 (SBRT): 24/3
  • RTOG 0412 (RT+chemo): 60/30
  • RTOG 0435 (RT+chemo): 60/30
  • RTOG 0522 (RT+chemo): 60/30
  • RTOG 0615 (RT+chemo): 66/33
  • RTOG 0617 (RT+chemo): 66/33

Anatomy

For contouring, see also Radiation_Oncology/Anatomy#Thorax

• 2010 PMID 20631370 Full text -- "Brachial plexus contouring with CT and MR imaging in radiation therapy planning for head and neck cancer." (Truong MT, Radiographics. 2010 Jul-Aug;30(4):1095-103.)
  • Good images

• RTOG; 2008 PMID 18448267 -- "Development and Validation of A Standardized Method for Contouring the Brachial Plexus: Preliminary Dosimetric Analysis Among Patients Treated with IMRT for Head-and-Neck Cancer." (Hall WH, Int J Radiat Oncol Biol Phys. 2008 Dec 1;72(5):1362-7.)
  • Delineation of brachial plexus established; images provided
  1. Identify and contour C5, T1, and T2.
  2. Identify and contour the subclavian and axillary neurovascular bundle
  3. Identify and contour anterior and middle scalene muscles from C5 to insertion onto the first rib
  4. To contour the brachial plexus OAR use a 5-mm diameter paint tool
  5. Start at the neural foramina from C5 to T1; this should extend from the lateral aspect of the spinal canal to the small space between the anterior and middle scalene muscles
  6. For CT slices, where no neural foramen is present, contour only the space between the anterior and middle scalene muscles
  7. Continue to contour the space between the anterior and middle scalene muscles; eventually the middle scalene will end in the region of the subclavian neurovascular bundle
  8. Contour the brachial plexus as the posterior aspect of the neurovascular bundle inferiorly and laterally to one to two CT slices below the clavicular head.
  9. The first and second ribs serve as the medial limit of the OAR contour
  • Validation study; 2012 PMID 21536393 -- "Validating the RTOG-Endorsed Brachial Plexus Contouring Atlas: An Evaluation of Reproducibility Among Patients Treated by Intensity-Modulated Radiotherapy for Head-and-Neck Cancer." (Yi SK, Int J Radiat Oncol Biol Phys. 2012 Mar 1;82(3):1060-4.)
    • Conclusion: "The RTOG-endorsed brachial plexus atlas provides a consistent set of guidelines for contouring this OAR with essentially no learning curve. Adoption of these contouring guidelines in the clinical setting is encouraged."

• Miami, 1996 PMID 8933882 -- "Radiation-induced brachial plexopathy: MR and clinical findings." (Bowen BC, AJNR Am J Neuroradiol. 1996 Nov-Dec;17(10):1932-6.)
  • Case report and literature review

Hyperbaric Oxygen

• UK MRC -- hyperbaric oxygen vs control
  • Randomized, Phase II. 34 patients, radiation-induced brachial plexopathy. Median time to onset 3 years, median time to HBO 11 years. Arm 1) hyperbaric oxygen: 100% oxygen @ 2.4 ATA x 100 minutes x 30 dives vs Arm 2) Control: same number and pressure, but gas mix equivalent to 100% oxygen at surface
  • 2001 PMID 11230889 -- "Double-blind randomized phase II study of hyperbaric oxygen in patients with radiation-induced brachial plexopathy." (Pritchard J, Radiother Oncol. 2001 Mar;58(3):279-86.)
    • Outcome: No difference up to 12 months post-treatment, though some improvement. Two cases with chronic lymphedema reported major and persistent improvement
    • Conclusion: HBO doesn't slow or reverse RIBP