MR guided adaptive radiotherapy for gastric MALT lymphoma

We delivered the UK’s first MR guided adaptive radiotherapy for gastric MALT lymphoma.

Radiotherapy to the stomach is challenging due to daily changes in the shape and volume of the stomach over the course of treatment, movement of the stomach with respiration and difficulty in visualising the stomach on daily non-contrast CT images on the treatment machine to guide accurate delivery of radiotherapy. A large margin (2-3cm) is typically applied to the stomach to overcome these challenges, resulting in a large volume of surrounding normal structures included in the radiation volume leading to increased toxicity.

MR guided adaptive radiotherapy for gastric MALT lymphoma overcomes all the three challenges that cause concern with gastric radiotherapy, allowing for an ultra-accurate treatment delivery with reduced toxicity.

Our first patient is a 39 year old male referred for involved site radiotherapy to Stage IA MALT gastric lymphoma. He had a planning MRI scan in inspiration breath hold to account for motion with respiration. An 8mm margin was given to the stomach. Treatment was planned with IMRT delivering 24Gy in 12# keeping doses to heart, kidneys and spleen as low as possible.

Daily adaptive radiotherapy requires recontouring of the stomach daily and we did find the shape and volume of the stomach on the 1st day of treatment to be very different from the planning scan and it was completely recontoured to reflect the shape and volume of the stomach on the day. Surrounding organs at risk, heart, kidneys, spleen, and spinal cord, were also amended as required. Treatment plan was re-optimised to get the best dose to the target and as low dose as possible to the surrounding organs. This step overcomes the challenge of the daily change in the anatomy of the stomach.

Treatment was delivered on our MRIdian platform, in breath hold, tracking the stomach in real-time and delivering radiation only when the stomach is within the defined boundary. This improves the accuracy of delivery allowing for opportunities to stop and amend where required. For example, on day 2, a gas bubble appeared during treatment which displaced the stomach out of the boundary, and we were able to see this, stop treatment and recontour and plan before restarting treatment.

Stomach (in red) movement with breathing in and out of the boundary margin (in yellow). Treatment is only delivered when stomach is within the boundary margin at inspiration breath hold.

MR guided adaptive radiotherapy allows for a more accurate delivery of planned treatment dose to reduced treatment volume compared to treatment on a conventional linac with reduced toxicity.

This is an exciting development in reducing radiotherapy related toxicity in young patients undergoing curative therapy.

If you would like more information about how to access MR guided radiotherapy treatments for your patients contact sabr@genesiscare.co.uk