How to Treat Double Synchronous Abdominal Metastases With Stereotactic MR-Guided Adaptive Radiation Therapy (SMART)?

Abstract

With the progress of systemic therapies, the opportunity to treat synchronous multiple abdominal lesions of unresectable oligometastatic patients is increasing. With a limited number of fractions and high dose per fraction, stereotactic radiotherapy (SBRT) is a treatment of choice in many indications. Magnetic resonance image-guided radiation therapy (MRgRT) offers a satisfying image quality and contrast especially for abdominal diseases. Indeed, this technique makes possible a daily adaptative radiotherapy (ART) in order to manage inter-fraction motion and live tumor visualization and gating to take into account intra-fraction motion. This work presents our experience in the management of SMART for double synchronous abdominal lesions treatment.Three patients have received a SMART for double synchronous abdominal lesions on our MR-Linac. Patient 1: a 43-years-old woman with two liver metastases from breast cancer. Patient 2: a 44-years-old man with two pancreatic metastases from leiomyosarcoma. Patient 3: a 45-years-old man with one liver metastasis and the pancreatic head primitive cancer. The proximity of the lesions was from 3.5 to 6.5 cm. The prescribed dose was 30 to 35 Gy in 5 fractions for pancreatic lesions and 40 to 60 Gy in 5 or 6 fractions for liver lesions. Patients have been selected according to their ability to hold and reproduce apneas. Each lesion has been treated in breath hold position on alternate days. A step-and-shoot intensity modulated radiation therapy (IMRT) technique has been initially planned for each lesion including an optimization volume permitting to reduce as low as possible the contribution to the second lesion. Each lesion has been gated on a unique sagittal slice with limited margin in the direction of the second lesion.For each patient, the treatment has been carried out properly in terms of comfort, respect of the limit of dose contribution to the second lesion and volume detection for the gating of the tumor. For patient 1, 2 and 3, no acute toxicity neither in-field progression has been reported, respectively 8, 7 and 6 months after the end of the treatment.Thanks to SMART, we have been able to define a feasible and robust methodology permitting double synchronous abdominal metastases treatment. The three patients have successfully followed up the treatment without identified comfort or technical issues. After minimum 6 months, no toxicity nor progression have been reported.M. Rouffiac: None. C. Chevalier: None. D. Thibouw: None. M. Quivrin: None. K. Peignaux-Casasnovas: None. G. Truc: None. L. Aubignac: None. J. Boudet: None. A. Petitfils: None. I. Bessieres: None.