Radiation Recall in Modern Oncology: Evolving Triggers and Treatment

BACKGROUND

Radiation recall phenomenon (RRP) is an acute inflammatory reaction confined to previously irradiated tissue, triggered by the subsequent administration of systemic anticancer agents, and distinct from concurrent radiosensitization. With the rapid integration of targeted therapies and immune checkpoint inhibitors (ICIs) into oncological practice, the clinical landscape of RRP has shifted, prompting the need for an updated, evidence-based synthesis of its pathogenesis, contemporary triggers, and optimal management strategies.

METHODS

A comprehensive literature search was conducted using PubMed, Scopus, and Web of Science for articles published between January 2015 and March 2026. Search terms combined “radiation recall,” “recall dermatitis,” and “recall pneumonitis” with “chemotherapy,” “targeted therapy,” “immune checkpoint inhibitor,” and individual drug names. Included were English-language peer-reviewed original articles, case series, and systematic reviews that reported clinical characteristics, mechanisms, or management of RRP in humans. Studies focusing solely on animal models or lacking clinical correlation were excluded. Over 50 relevant publications were critically appraised and synthesized narratively.

RESULTS

Radiation recall dermatitis accounted for approximately 85% to 90% of all events, while recall pneumonitis represented 3% to 5%, and mucositis or myositis was rare. Taxanes, particularly docetaxel, and anthracyclines remained the most frequently implicated cytotoxic agents, with incidence rates reaching 6% to 10% in specific cohorts. Among newer therapies, vemurafenib, everolimus, and the ICIs pembrolizumab and nivolumab were increasingly reported triggers, often producing prolonged or severe reactions. Risk factors consistently identified included cumulative radiation doses above 20 Gy and a latency of less than 2 months between radiotherapy and drug exposure, though cases occurring years later were documented. Pathophysiological findings highlight a triad of impaired epithelial stem cell reserve, microvascular rarefaction with chronic hypoxia, and a localized surge of proinflammatory cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α. ICI-induced recall further involves reactivation of radiation-primed T cells against tissue-restricted antigens. Immediate corticosteroid therapy—topical for mild dermatitis and systemic (eg, prednisone 0.5-1.0 mg/kg) for severe or visceral involvement—was the therapeutic cornerstone. Rechallenge with the offending agent succeeded in 70% to 80% of cases when accompanied by a 20% to 25% dose reduction, prophylactic corticosteroids, or extended intervals between treatments.

CONCLUSIONS

RRP in the current era is increasingly linked to targeted and immunotherapeutic agents, demanding heightened clinical suspicion. Optimal management rests on prompt drug interruption, aggressive anti-inflammatory therapy, and individualized rechallenge protocols. Recognizing the underlying immune-mediated memory of irradiated tissue opens avenues for predictive biomarker development and prophylactic interventions, ensuring that this paradoxical reaction does not interrupt essential anticancer care.