Lipiodal Injection Technique for Free Flap Sparing Adjuvant RT Planning in HNC

Lipiodal is approved and indicated for subcutaneous injection in children and adults for the purposes of lymphatic mapping.12 Free flap reconstruction in the head and neck typically uses fasciocutaneous flap comprising skin, dermis, subcutaneous tissue and deep fascia. Composite reconstructions can also include vascularised muscle and bone. Bone margins are well defined on pre- and post-operative imaging. However, it is the soft tissue muco-cutaneous margins in the oral cavity and pharynx in particular that are less reliable on post operative imaging due to effects of post-operative edema and gravity/positional dependence. Thus, injecting a liquid fiducial marker such as Lipiodal to the margins of the free flap in the dermal/subcutaneous plane will be of maximal benefit in delineating margins of healthy flap tissue and tumour bed for the purposes of post-operative radiation planning. This type of injection to the dermal/subcutaneous tissue is currently routinely performed in interventional radiology at London Health Sciences Centre at Victoria Hospital for lymphography and meets with approved clinical indications for use in Canada and at our institution.

Ten patients with locally advanced (T2-T4) oral cavity squamous cell carcinoma undergoing primary surgical resection with free flap reconstruction and adjuvant radiation therapy will be recruited for the study and treated with standard of care surgery and adjuvant treatment as per the London Regional Cancer Program Head and Neck Tumour Board recommendations at Victoria Hospital. Patients with previously treated locally advanced head and neck malignancy (either with surgery and/or radiotherapy) will be excluded from the study. Patients not requiring free flap reconstruction will be excluded from the study.

Patients will be injected with Lipiodal at the time of resection of their head and neck tumours. Injections will be delivered using a 22G needle on a 10ml syringe. Each injection will be 0.5ml aliquot delivered trans epidermal to the subcutaneous margin of the free flap, 2-3mm within the free margin. This will provide constancy in tissue type being injected and allow visualisation of an epidermal wheal as confirmation of successful injection. This volume will allow up to 20 injections to be equally spaced circumferentially around the free flap thus defining the interface with the tumour bed.

Patients will be followed closely post-operatively as an inpatient for 7-14 days as per standard of care with at least twice daily visual reviews of the flap, assessing perfusion, inflammatory change (such as dermatitis or lipogranuloma) and healing progress at the flap inset margin. Early post-operative CT scan will be performed at day 5 post-op as per standard of care, which will opportunistically allow assessment of Lipiodal delivery to the tumour-bed/free-flap interface and also ensure no local complication. Upon discharge, patients will be followed closely with reviews at 1-, 4-, and 8-weeks post-operatively as per standard of care. Patients will receive a post-operative planning CT scan under the supervision of the treating radiation oncologist as per standard of care at 6-8 weeks post-operatively.

Inclusion criteria

• Adult patients (18 years and older) seen at the head and neck clinic at London Health Sciences Centre (LHSC)
• Locally advanced T2-4N0-3M0 mucosal or cutaneous squamous cell carcinoma involving the oral cavity requiring composite resection and free flap reconstruction

Exclusion criteria

• Previous treated locally advanced head and neck cancer with surgery and/or radiation
• History of hypersensitivity or adverse reaction to Lipiodal or any iodinated radiocontrast
• Severe bronchial asthma
• Severe renal dysfunction
• Hyperthyroidism
• Pregnant
• Breastfeeding
• Clinically apparent cognitive impairment