Radiation Recall Phenomenon Following Vaccination in a Patient with Prior Radiation for Sarcoma

Summary: Radiation recall phenomenon (RRP) or radiation recall dermatitis (RDD) is a rare inflammatory skin reaction occurring in a previously irradiated area following exposure to triggers like chemotherapy, vaccination, antibiotics, or iodine [1,2]. Traditionally associated with chemotherapy, RDD has been linked to mRNA COVID-19 vaccines [1]. Understanding vaccine-induced RRP is crucial for patients undergoing radiation therapy. A patient developed an RRP skin reaction in an area previously irradiated after receiving several routine viral vaccinations. A 67-year-old female with a history of low-grade liposarcoma of the right thigh underwent resection in 2008, followed by a local recurrence treated with a resection in 2010 and adjuvant radiation (50 Gy in 25 fractions, plus a 10 Gy boost, figure 1). In 2021, she presented with another local recurrence of dedifferentiated liposarcoma, leading to resection without adjuvant treatment. Pathology revealed dedifferentiated liposarcoma, pT4N0, grade 3. Surveillance imaging revealed a prominent right axillary node, prompting a mammogram that identified a 7 mm invasive lobular carcinoma (ILC) of the right breast, grade 2, ER/PR positive, Her2 negative, with Ki-67 of 20% (cT1bN0M0). She underwent lumpectomy and sentinel lymph node biopsy, showing pT1bN0 with negative margins. The patient received hypo-fractionated whole breast radiation (40.05 Gy in 15 fractions, plus a 10 Gy boost). During this period, she did not receive systemic chemotherapy, or any drugs known to cause RRP. On her 12th fraction, she developed a blister on her right thigh, resembling a reaction during her sarcoma radiation in 2010 (figure 2). Three days prior, she received her COVID-19 Moderna, RSV, and influenza vaccines. The blister ulcerated over the next few days but resolved with wound care after two months. Importantly, her pre-existing grade 1 radiation dermatitis in the breast did not worsen after vaccination. This case illustrates that vaccines can trigger RRP, which was limited to the older radiation site, while the breast field showed no exacerbation. RRP occurs in more intensely treated areas following several radiation courses [3]. Interestingly, her reaction was a blister and not traditional dermatitis. Reports exist of bullous pemphigoid reactions years after radiation [4]. Early diagnosis and management of RRP can minimize complications and improve outcomes. Further research is needed to explore the mechanisms behind RRP and its variability. Anna Chung (she/her/hers), BS (Presenting Author) - UT Southwestern Medical School; Asal Rahimi, M.D. (Co-Author) - UT Southwestern Medical Center, Department of Radiation Oncology; Narine Wandrey, M.D. (Co-Author) - UT Southwestern Medical Center, Department of Radiation Oncology; Mona Arbab (she/her/hers), M.D. (Co-Author) - UT Southwestern Medical Center, Department of Radiation Oncology