A Dosimetric Comparison of IMRT and 3D-CRT Using Deep Inspiratory Breath Hold (DIBH) and Free-Breathing (FB) Techniques in Gastric Mucosa Lymphoid Tissue Lymphoma (MALT)

Abstract

Definitive radiation therapy (RT) is a curative treatment modality for gastric MALT. Reducing radiation dose to organs at risk (OAR) is imperative for patients with curative disease and excellent long-term prognosis. Advanced RT planning with DIBH and/or IMRT is available to improve the therapeutic ratio of RT by minimizing dose to normal tissues while maintaining adequate target coverage. We aimed to compare dosimetric parameters when using different radiation planning and delivery techniques in patients with gastric MALT.After institutional review board approval, we identified adult patients (age ≥ 18 years) with biopsy-proven gastric MALT who were treated at our institution from 2010 to 2020. Each patient underwent two simulation CT scans: free breathing (FB) and DIBH. Four plans were generated for each patient including DIBH-IMRT, DIBH-3DCRT, FB-IMRT, and FB-3DCRT with a prescribed dose of 30 Gy in 20 fractions. The CTV was defined as the entire stomach including the gastroesophageal junction to the pylorus. The PTV included a 1 to 1.5 cm expansion from the CTV. Paired t-tests were used to compare mean calculated dose values for each OAR based on treatment technique.Our cohort consisted of 8 patients (6 male, 2 female) with a median age 62.5 years (39 to 83 years). Compared to 3D-CRT, IMRT was associated with significantly decreased heart dose for both DIBH (Dmean 354.7 vs 440.5 cGY, P = 0.029) and FB (Dmean 521.2 vs 699.6 cGY, P = 0.006). IMRT was also associated with decreased dose to the left ventricle (LV), left anterior descending artery (LAD), liver, and lungs compared to 3D in both FB and DIBH. For IMRT plans, DIBH was associated with significantly lower heart V30 and V20 and a trend towards significance for lower heart Dmean (354.7 vs 521.2 cGY, P = 0.059) in comparison to FB. For 3D plans, DIBH was associated with a lower heart V30 and V20, and a higher lung V20, V10, and V5 in comparison to FB.Both IMRT and DIBH represent modalities for reducing heart dose in gastric MALT patients receiving definitive RT. IMRT also reduces LV, LAD, liver and lung dose regardless of technique used to account for respiratory motion whereas DIBH was not associated with reduced doses to the LAD, kidney, or liver.