Analysis of modern versus conventional radiotherapy techniques for gastric mucosa-associated lymphoid tissue (MALT) lymphoma

Localized MALT (gMALT) lymphoma patients are primarily treated with radiotherapy (RT). Considering the different resource capabilities of departments globally, the incremental benefits with modern techniques has not yet been determined. Here we report dosimetric differences of current RT techniques. Twelve stage IE gMALT patients treated with RT between January 2011 and December 2016 were analyzed. RT planning were recreated for conventional (parallel-opposed, 3D-conformal-RT [3D], 3D-field-in-field [3DFIF]) and modern techniques (volumetric-modulated-arc-therapy [VMAT], intensity-modulated-RT, helical tomotherapy). Prior to treatment, patients fasted for 4 h. RT prescription dose was 30Gy in 20 fractions. Planning target volume (PTV) was defined as entire stomach with 1–2 cm isometric expansion. OARs (heart, kidneys, liver and cord) constraints were determined according to QUANTEC. Dosimetric data were summarized and compared. Median age was 65.5y (range, 50–78). At the median follow-up of 70.5 m all patients are alive with no disease relapse post-RT nor any grade ≥3 treatment side effects. Compared to conventional RT, modern RT techniques were similar in providing excellent dose distribution and all OARs sparing. Specific to PTV coverage, VMAT was superior compared to 3DFIF (p < 0.001) and 3D (p ≤ 0.008). However, PTV coverage improvement was not clinically relevant. In OAR sparing, VMAT had better heart-sparing effect than 3DFIF (p < 0.01) or 3D (P < 0.01). Specific to kidneys, all 3 techniques fulfilled constraints. All techniques fulfilled cord and liver constraints. While modern RT techniques offer significant advantages, conventional techniques were sufficient to achieve good target volume coverage and reduce dose to the OARs in most patients. Some individuals, such as those with challenging anatomy, may be good candidates for modern approaches. The insights gained from this study can be used to optimize 3D or 3D field-in-field (3DFIF) plans for these patients. With recent data showing good outcomes with lower RT doses, it also would be important to investigate the utility of advanced techniques globally.