A CT scan of the chest (Fig 1
, top) showed an invasive 6.5 × 8-cm anterior mediastinal mass encasing the superior vena cava and adherent to the aorta and pulmonary artery. This mass was evident on a positron emission tomographic (PET) scan (Fig 2
, top, A to D). Fine-needle aspiration and core biopsy confirmed a diagnosis of invasive thymoma (Masaoka stage III). She was treated with an IV chemotherapeutic regimen consisting of cisplatin, 50 mg/m2; doxorubicin, 50 mg/m2; and cyclophosphamide, 500 mg/m2, with amifostine, 1,000 mg. To minimize cardiac toxicity, doxorubicin was administered as a continuous infusion over 96 h rather than as a bolus. Amifostine was added to reduce the risk of cisplatin-induced peripheral neuropathy, which could potentially devastate a person with a preexisting myopathy. A total of six cycles was administered at three weekly intervals. Cardiac function was monitored by serial echocardiography and multigated equilibrium radionucleotide cineangiography and remained normal. Cardiac medications were gradually withdrawn. The tumor shrank approximately 90% after four cycles and plateaued. External beam radiotherapy to the chest followed. A total of 3,960 cGy was administered in 22 fractions (anteroposterior/posteroanterior field), followed by a boost of 900 cGy using oblique fields to avoid the spinal cord and heart. A repeat PET scan (Fig 2, bottom, A to D) on completion of all therapy showed no evidence of the thymoma despite a residual 2 × 3 cm mass on CT scan (Fig 1, bottom). The patient tolerated the therapy very well and remains in remission 19 months after diagnosis. The myotonic dystrophy is unchanged.