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In this case, radiation dermatitis (RD) is characterized by a differential response in 2 developmentally equivalent tissues from distinct anatomic locations.
A man in his 50s presented with a gradually enlarging erythematous patch on the upper chest overlying an area of surgery performed 12 years before for the removal of a neurotropic basal cell carcinoma (Figure A). Computed tomographic–positron emission tomographic scans revealed an infiltrative mass (10 cm) invading the osseous structures of the anterior chest wall and soft tissues of the neck, which prompted their radical resection. This was followed by reconstruction with an autologous myocutaneous free flap harvested from the anterolateral thigh (Figure B). After an uncomplicated 3-month postoperative course and flap “take,” a cumulative radiation therapy (RT) dose of 66 Gy (33 fractions) was delivered over 6.6 weeks.
A, Prior to surgery, an infiltrative basal cell carcinoma of the upper chest had invaded the sternum, manubrium, left clavicle, and soft tissues of the anterior mediastinum and neck. B, Clinical image taken after autologous myocutaneous free flap reconstruction, following radical resection of the anterior chest wall and bilateral neck dissection. C, Grade 2, radiation dermatitis manifesting as brisk erythema with dry desquamation over the neck and upper chest; note the marked sparing of the skin within the flap (inset).
During RT, the patient reported a pruritic, erythematous eruption outside the flap, but within the RT target volume. The eruption conspicuously spared the skin of the free flap. At an RT dose of 56 Gy in 23 fractions (5.6 weeks from start of RT), the patient developed a grade 2 RD outside the flap (Figure C). A grade 1 RD was noted over the flap, consisting of faint erythematous papules. In vivo dosimetry of sites exhibiting the differential pattern (Figure C, inset) excluded inconsistent dosing. Cultures from outside the flap in areas with erythema and pustules grew methicillin-sensitive Staphylococcus aureus. A 5-day course of oral antibiotics and topical corticosteroids improved the symptoms, with complete resolution by 12 weeks without recurrence.
The reasons for RD relatively “sparing” skin within the transplanted flap are unknown. In a small series, the response of autologous split- and full-thickness grafts to RT ranged from pronounced radiosensitivity to relative radioresistance; fresh grafts (<3 months old) were prone to developing brisk and more vigorous reactions than normal skin, while older grafts (>1 year old) tended to be relatively radioresistant.1- 3 The tolerance to RT was similar in grafts that were 3 months to 1 year old, and differential reaction patterns were not described. It was noted that recovery from RD may be delayed in fresh grafts or absent in old grafts.
Similar studies involving flaps are sparse. Wang et al4 found that the rate of acute toxic effects in some reconstructed free and pedicle flaps was significantly lower (radioresistance) than in the surrounding normal tissues, and they attributed it to mild tissue hypoxia. Also, in his discussion, Withers5 noted that myocutaneous flaps and free flaps showed less skin damage from postoperative radiation than skin grafts and pedicle flaps, which suggests that the response to radiation is dependent on graft and/or flap vascularity, as shown in rat the models described by Sumi et al.6
The effect of the anatomical origin of transplanted skin has not been considered a factor influencing the development of RD. In our patient, RT was administered 3 months after a microsurgical flap reconstruction. Although this leads to the restoration of vascular and lymphatic flow within days,7 the extent of revascularization and immune surveillance in the skin of flaps is not known. Scar remodeling peaks at around 3 to 6 months. It is not clear whether any of these factors might have affected inflammatory responses (free radical generation) in flap skin due to disruption of collateral processes or poor inflammatory cell trafficking to locoregional nodes. The role of variations in regional skin thickness (thicker in the thigh [54.3 μm] vs the chest [37.6 μm]), prior sun exposure (chest > thigh), severance of neural networks, and bacterial flora needs to be determined.
Our observations suggest that the anatomic-physiologic condition of the irradiated native skin, or its competence, has a clear role in determining the outcome.
Corresponding Author: Mario E. Lacouture, MD, Dermatology Service, Memorial Sloan-Kettering Cancer Center, Rockefeller Outpatient Pavilion, Ste 228, 160 E 53rd St, New York, NY 10022 (firstname.lastname@example.org).
Published Online: August 6, 2014. doi:10.1001/jamadermatol.2014.888.
Conflict of Interest Disclosures: Dr Lacouture has served as a speaker, consultant, or advisor with Advancell, AstraZeneca, Aveo, Bayer, BergPharma, Bristol-Myers Squibb, Galderma, Genentech, Genzyme, GlaxoSmithKline, Helsinn, Imclone, Lilly, LindiSkin, Merck, Novocure, Novartis, Onyx, Pfizer, Roche, Sandoz, Sanofi Aventis and Wyeth. Dr Barker serves as a consultant to RP Pharmaceuticals.
Additional Contributions: We are indebted to Ying Zhou, MS, for assistance with in vivo dosimetry.
Belum VR, Hill A, Matros E, Lacouture ME, Barker CA. Differential Radiation Dermatitis in Native Skin and an Autologous Transplanted Myocutaneous Flap. JAMA Dermatol. 2014;150(12):1365-1367. doi:10.1001/jamadermatol.2014.888