Iris Metastasis from Small-Cell Lung Cancer

Abstract

®54-year-old man underwent computed tomography and was suspected of having lung cancer. The patient underwent video-assisted thoracoscopic partial lobectomy and was histopathologically diagnosed with small-cell lung cancer. For the treatment of the residual tumor, including the metastatic mediastinal lymph nodes, he subsequently received chemoradiotherapy combined with chemotherapy (cisplatin and etoposide) and radiotherapy at a total dose of 60 Gy delivered in 30 fractions. The patient was successfully treated and had a complete response. However, at 4 months after surgery, blurred vision was evident in the right eye; a mass measuring 5 mm in size was observed in the right iris using slit lamp microscopy. No abnormalities were found in the ocular fundus, including the retina, and ocular tension. The corrected visual acuity was measured at 0.9 in the visual acuity test using the Landolt ring chart; this corresponded to 18 of 20 in the Snellen chart. The patient was diagnosed with iris metastasis. No other diseases were detected on chest and abdominal computed tomography, head magnetic resonance imaging, and bone scintigraphy. Subsequently, chemotherapy with cisplatin and etoposide was administered. The metastatic tumor exhibited a transient reduction in size but then regrew. Consequently, the patient received radiotherapy with 7-MeV electrons through an anterior port for treatment of the iris metastasis. Because the patient was treated with radiotherapy without computed tomography simulation, for reference, dose distribution curves obtained using a representative radiotherapy simulation model are shown in Fig. 1. Daily fraction size was 2 Gy, 5 days per week, and the total dose was 40 Gy delivered in 20 fractions. A bolus with a 5 mm water-equivalent thickness was used to compensate for the surface dose in the tumor. The overall treatment time was 30 days. The tumor volume decreased rapidly after the initiation of radiotherapy and had completely disappeared by the completion of treatment (Fig. 2). Regarding acute toxicities, the patient had mild radiation keratitis, conjunctivitis, and dermatitis; however, these reactions had all resolved shortly after the completion of radiotherapy.