Radiation Recall

Radiation Recall (RR)

Definition

• Radiation recall is an acute inflammatory reaction that occurs in previously irradiated tissue after administration of certain systemic agents (chemotherapy or targeted therapy).
• The reaction “recalls”” the prior radiation site, even weeks, months, or occasionally years after radiation.
• It is not a continuation of radiation toxicity, but a triggered inflammatory response.

Typical Clinical Manifestations

• Skin: erythema, rash, desquamation, pruritus (most common)
• Other tissues: mucosa (mucositis), lungs (pneumonitis), GI tract (enteritis), muscle (myositis)
• Severity: ranges from mild redness to severe ulceration; usually limited to irradiated field

Common Triggering Drugs

• Chemotherapy:
  • Dactinomycin, doxorubicin, paclitaxel, gemcitabine, capecitabine, 5-FU
• Targeted therapy / TKIs:
  • Sorafenib, sunitinib, vemurafenib, vemurafenib + cobimetinib
• Immunotherapy: rare, but reported with checkpoint inhibitors

Onset

• Typically days to weeks after drug administration, but can occur months or even years after radiation.
• Can occur after a single dose or cumulative exposure.

Management

1. Discontinue or hold triggering agent if reaction is severe
2. Supportive care:
   • Topical corticosteroids (skin)
   • Systemic corticosteroids (severe inflammation)
   • Analgesics, wound care as needed
3. Dose modification / rechallenge:
   • Mild reactions may allow reintroduction at reduced dose
   • Close monitoring for recurrence

Pharmacist Considerations

• Identify at-risk patients: previous radiation + current chemotherapy or targeted therapy
• Patient counseling: advise patients to report erythema, pain, or other reactions in previously irradiated areas
• Drug interactions: none direct, but consider overlapping toxicity with other agents (e.g., myelosuppression, mucositis)
• Documentation: ensure prior radiation fields are known to anticipate recall reactions

Summary

Radiation recall is a drug-triggered inflammatory reaction in previously irradiated tissue, commonly caused by chemotherapeutics or targeted agents. Pharmacists play a key role in prevention, early recognition, patient counseling, and management, including holding therapy, supportive care, and careful rechallenge.