Spatially fractionated grid radiotherapy: Experiences at inmol hospital

Objective:

Spatially Fractionated Radiotherapy (SFRT) is known for its highly potent immunomodulated response that contributes to its highly effective outcomes. This makes SFRT one of the few promising treatment options for conquering tumors, especially in locally advance cases in palliative setting for symptomatic controls. It used a novel and practical volumetric modulated arc therapy (VMAT) planning approach for grid therapy

This study aims to report our early experiences of using SFGRT for patients with various cancers in our hospital

Methods and Materials:

Dose is prescribed to 1.5-cm diameter spherical contours placed throughout the gross tumor volume (GTV). Placement of spheres is variable, but they must maintain at least a 2cm (center to center) separation, and the edge of any sphere must be at least 1 cm from any organ at risk (OAR). Three concentric ring structures are used during optimization to confine the highest doses to the center of the spheres and maximize dose sparing between them. The end result is alternating regions of high and low dose throughout the GTV and minimal dose to OARs. High-intensity flattening filter-free (FFF) modes are used to efficiently deliver the plans, and entire treatments typically take only 15 to 20 minutes.

 Results:

A total of 4 patients with various cancer types were treated using SFGRT, with a median age of 47.5 years old males ,2 cases of sarcoma,1 case of mediatinal lymphomaand 1 case of chordoma. The approach is illustrated with 2 examples treated at our institution. Patient #1 had a 1703-cm3 mediastinal mass and was prescribed 20 Gray (Gy) to 24 spherical regions within the GTV. Patient #2 had a 3680-cm3 abdominal tumor and was prescribed 18 Gy to 32 spherical regions within the GTV. Both patients received additional consolidative radiation approximately 1 week after the initial VMAT grid treatment. Each patient experienced marked reduction in tumor size and symptomatic relief without treatment-related complications. All cases were palliative intent aimed at pain relief, bleeding control, or bulky mass reduction. Outcomes are mostly satisfactory with 86% of pain palliation, 77% bleeding control, and 60% mass decreased in size, with 2 had partial response.

Conclusions:

SFRT shows promising results in terms of tumor response, especially for bulky tumor. Proper utilization of SFRT can improve tumor response. Our experience showed satisfactory treatment results for the the patients. Additionally, no significant toxicities were found in all of our patients.. As many centers offer VMAT treatments, the approach is widely accessible and can be readily implemented once appropriate patient selection and delivery processes are established.

To be updated shortly..