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An unusual case of gemcitabine-induced radiation recall.

Radiation recall is an uncommon inflammation of a previously irradiated area, incited by subsequent exposure to a drug. It is triggered most commonly by chemotherapeutic agents, but also by tamoxifen, anti-TB medications, and simvastatin. We report an unusual case of postirradiation myositis potentiated by gemcitabine to alert clinicians to consider radiation recall when confronted with muscle complaints in this context. Our limited experience suggests that continued oral prednisone may control symptoms and allow continuation of needed gemcitabine therapy despite radiation recall muscle inflammation. A 54-year-old woman with lung adenocarcinoma received palliative radiation therapy to 30 Gy in 10 fractions to her left ribs, left sacroiliac, and left hip-acetabulum. One month later, she began gemcitabine therapy (1000 mg/m/dose). Two months after chemotherapy began, she developed persistent discomfort in her left hip and buttock. On examination, there was tenderness to palpation of the left hip and buttock without skin lesions. Magnetic resonance imaging (MRI) (Fig. 1) demonstrated muscle edema with high STIR signal density in the same distribution as the prior radiation; a sharp medial border of normal and abnormal gluteal muscle corresponded to the border of the radiation portal and was not suggestive of other muscle disease. Metastatic lesions were present to the iliac bones, sacrum, and left hip/buttocks. Serum CPK was elevated at 1129 IU/L (normal 20–165). Oral prednisone titrated to relief of muscle complaints permitted continuation of gemcitabine treatment of the planned 7-month course. Symptoms and CPK levels correlated with changes in prednisone dosage, worsening as prednisone was tapered and improving with increasing doses. Myositis secondary to gemcitabine-induced radiation recall may mimic or coexist with metastases, or be misdiagnosed as an incidental musculo-skeletal injury, hypercoagulabilityrelated venous thrombosis, or paraneoplastic myopathy. The majority of previously reported cases presented as dermatitis or mucositis and more rarely involved muscle, colon, esophagus, lung, or optic nerve. Previous reports with small sample size indicate that gemcitabine differs from more common offending drugs, the anthracyclines, doxorubicin, and actinomycin-D; radiation recall complicating the latter agents typically involves the skin and occurs much later after radiation with a mean time of onset of hundreds of days after radiation versus less than 2 months for gemcitabine. A common treatment of radiation recall is withdrawal of the offending agent, although rechallenge has been successfully documented. Our single case suggests that, at times, oral steroids may facilitate continuation of needed gemcitabine despite clinical myositis.