A first report of tumour-tracking radiotherapy with helical tomotherapy for lung and liver tumours: A double case report

Abstract

There are only a limited number of previous reports on clinical cases using tumour tracking with tomotherapy. Therefore, we present two cases of patients treated with tumour tracking with tomotherapy. First, a 74-year-old man with an inoperable lung cancer type T1bN0M0 underwent stereotactic body radiotherapy at a total dose of 48 Gy in four fractions. Second, a 68-year-old man with hepatocellular carcinoma with a portal venous tumour thrombosis and history of liver stereotactic body radiotherapy with fiducial marker implantation received radiotherapy at a total dose of 48 Gy in 20 fractions. The results of patient-specific quality assurance and tracking radiotherapy were sufficient to irradiate tumours. Tumour tracking with tomotherapy successfully delivered radiation in a total of 24 treatment fractions in both patients. Tumour tracking with tomotherapy is feasible in lung and liver cancer treatment. This study's findings suggest the clinical use of tumour tracking with tomotherapy.

Keywords: Tomotherapy; lung cancer; stereotactic ablative radiotherapy; stereotactic body radiation therapy; tumour tracking.

Figure 1.

Computed tomography (CT) scanning diagnostic images of lung cancer and the treatment plan. (a) CT images revealed a solitary nodule of 20 mm in diameter in the lower lobe of the right lung (left panel). High 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) uptake by the tumour was observed in contrast imaging with positron emission tomography with FDG integrated with CT (¹⁸F-FDG PET/CT) images (right). (b) Stereotactic body radiation therapy (SBRT) plan was generated with a total of 48 Gy in four fractions for planning target volume (PTV). The colour washes indicate the dose distributions. (c) Results of tracking accuracy in stereotactic body radiation therapy for lung tumour (upper left). Tracking results at first simulation without coaching (upper right); results at second simulation with audio coaching (lower left); results at first treatment fraction (lower right) and results at treatment completion (fourth fraction). Findings indicate improvement in tracking accuracy after the first simulation. Parameters of interest (Potential Diff and Measured Δ) did not exceed threshold values for most of the treatment time. Treatment course was successfully completed.

Figure 2.

Diagnostic images and treatment plan for liver tumour. (a) The previous SBRT was prescribed at a dose of 40 Gy in five fractions (D95) for pathologically confirmed HCC in S4 of the liver. Dose distribution of previous stereotactic body radiation therapy was represented in the MIM Maestro version 7.0.3 (MIM Software Inc., Cleveland, OH, USA) from the digital imaging and communications in medicine-radiation therapy (DICOM-RT). (b) Portal venous tumour thrombosis (PVTT) observed close to the previously irradiated area in contrast-enhanced computed tomography (indicated by arrows). (c) Treatment plan with intensity-modulated radiation therapy for PVTT was generated at a total of 48 Gy in 20 fractions for planning target volume (PTV). (d) Combined dose distributions of previous and present radiotherapy defined in terms of biologically effective dose (BED), using a linear-quadratic model with an assumed α/β ratio of 2 Gy for liver (BED₂) (MIM Maestro). (e) Results of tracking accuracy in radiotherapy for liver tumour (upper left). The first simulation resulted in an unstable model (upper right); a stable model was achieved after changing the LED marker position from the chest wall to abdominal wall (lower left); results at first treatment fraction (lower right) and results at treatment completion (20th fraction). Parameters of interest (Potential Diff and Measured Δ) never exceeded threshold values, except for the first simulation. Treatment was successfully completed.