The single, fractional, high-dose stereotactic radiation therapy procedure was described in detail elsewhere. Briefly, the patient is fixed noninvasively in a custom-made bed, and CT images at the end-expiratory phase are obtained about 20 cm caudally and rostrally from the tumor with the patient lying in the custom-made bed. Isocentric, multiportal, three-dimensional, converging radiotherapy is planned, and a single dose of radiation therapy is delivered only at the end-expiratory phase using 6-mV x-rays. The subjects in the present study were 16 patients with lung tumors who were undergoing single, fractional, high-dose, stereotactic radiation therapy with sequential measurements of serum KL-6 (Table 1
). None of the tumors were treated by fractionated radiation. Eight patients had metastatic lesions from various primary sites, and six patients had primary lung cancer. The remaining two patients had a solitary lung tumor of unknown histology, although the accumulation of fluorodeoxyglucose in positron emission tomography strongly suggested diagnoses of primary lung cancer. There were six squamous cell carcinomas and six adenocarcinomas. The patients ranged in age from 53 to 90 years, with a median of 73 years. The female/male ratio was 6:10. Circular fields of the following diameters were used for stereotactic irradiation: 50 mm in seven patients; 40 mm in five patients; and 30 mm in four patients. The minimum dose of the gross tumor volume was 35 Gy in 2 patients, 30 Gy in 12 patients, and 20 Gy in 2 patients. The volume irradiated > 8 Gy was defined as V8, because single-fraction irradiation at this dose was reported previously5
as causing RP in humans at a significant rate. V8 ranged from 28 to 306 mL, with a mean of 132 mL. Three patients underwent concurrent chemotherapy with irinotecan (CPT-11). Five patients had chronic lung disorders. Three patients had emphysema, and two patients had chronic bronchitis. The length of follow-up ranged from 2 to 20 months, with a mean of 6 months. During the follow-up period, 14 tumors remained stable, while 2 showed local regrowth. Serum levels of KL-6 were measured by a modified sandwich-type enzyme-linked immunosorbent assay.3,6–7
Serum levels of KL-6 were measured before irradiation and every 1 or 2 months after irradiation, as shown in Figure 1
. The cutoff level of KL-6 was 500 IU. Differences between groups were tested by t test or χ2 test, and p values of < 0.05 were considered to indicate significance.