Real-time tumor-tracking radiation therapy for lung carcinoma by the aid of insertion of a gold marker using bronchofiberscopy

Abstract

Background: The authors developed fluoroscopic real-time tumor-tracking radiation therapy (RTRT) by insertion of a gold marker using bronchofiberscopy to reduce uncertainties in organ motion and set-up error in external radiotherapy for moving tumors. The purpose of the current study was to evaluate RTRT's feasibility in lung carcinoma treatment.

Methods: The three-dimensional position of a 1.0-2.0 mm gold marker in or near the tumor was detected by two sets of fluoroscopies every 0.03 seconds. The treatment beam was gated to irradiate the tumor only when the position of the marker coincided with its planned position using the RTRT system. Bronchofiberscopic equipment for insertion of the marker into the lung tumor was developed and used for 20 lung tumors in 18 patients. Patients were given high dose hypofractionated focal irradiation (35-48 Gy in 4-8 fractions in 4-10 days) with a planning target volume margin of 5 mm for the tumor.

Results: The markers were successfully inserted and maintained at the inserted position during and after the radiotherapy in 14 (88%) of 16 peripheral-type lung tumors and in none of four central-type lung tumors, indicating that this method of RTRT was not feasible for central-type lung tumors. Tracking of the marker was successfully performed in 1 of 2 tumors with a 1.0 mm marker and in all of 12 tumors with a 1.5-2.0 mm marker. On the whole, 13 (65%) of the 20 tumors were successfully treated with RTRT. Local tumor control was achieved and maintained for all 12 patients (13 tumors), who were treated with RTRT, with a median followup of 9 months (range, 5-15). Localized radiation pneumonitis was found radiographically at the lung volume that was irradiated with about 20 Gy, without symptoms in all but one patient.

Conclusions: The insertion of a gold marker into or near peripheral-type lung tumors using bronchofiberscopy is a feasible and safe technique. Excellent initial response and low incidence of clinical complications suggest that the high dose hypofractionated focal irradiation using the RTRT system can be a good local treatment for peripheral-type lung tumors.