DIBH vs. EEBH for gastric lymphoma

Keywords: Gastric Lymphoma, DIBH, EEBH, Cardiac Dose Introduction: Radiotherapy is an important treatment for gastric lymphoma [1] but can result in a significant radiation dose to the heart. Treating in breath-hold allows margin reduction [2] and increase stomach-heart distance. However it is not known whether this separation is greater in inspiration or expiration. We investigated the relationship between the breath-hold phase and heart-stomach distance. Method: We conducted a 2-part study. In part [A] we compared the distance between the inferior extent of the heart and the superior extent of the stomach in inhalation and exhalation phases in 50 abdominal 4DCT scans. In part [B] we evaluated the stomach-heart distance in 20 cases scanned in deep-inspiration breath-hold (DIBH), in comparison to free-breathing (FB) scans of the same patients and 20 different cases scanned in end-expiration breath-hold (EEBH). Results: Of the 50 4DCT datasets evaluated, the heart-stomach distance was greater in inspiration than expiration in 37/50 cases (74%) and equal in 9/50 (18%). The difference in mean heart-stomach distance is 0.56cm (-0.25cm – 3.25cm, median 0.5cm) greater in inhalation phase than exhalation phase in the whole population; and 0.71cm (0.25 – 3.0, median 0.5cm) in the 74% showing greater distance in inhalation phase. Of the 4 patients the difference in distance was 0.25cm (1 slice). Analysis of the DIBH datasets showed the mean heart-stomach distance was 1.08cm (0cm – 3.75cm, median 0.88cm) greater in DIBH compared to FB (same patients). 85% of cases showed a greater distance in DIBH with no difference in the remaining 15%, and no cases showing a smaller distance. A comparison between the DIBH and EEBH datasets (different patients) showed the mean heart-stomach distance was 1.08cm greater in DIBH than EEBH. Interestingly, the mean EEBH distance was the same as the mean FB distance. Conclusion: Our analysis shows that the heart-stomach distance is most often greater in the inhalation phase compared to exhalation phase during the normal breathing cycle. DIBH results in more than double the mean separation of stomach and heart compared to free breathing and is likely to result in greater separation than EEBH. Numerical References [1] Aleman, Haas & van der Maazen (2010) 'Role of radiotherapy in the treatment of lymphomas of the gastrointestinal tract', Best Practice and Research: Clinical Gastroenterology, 24(1), pp. 27-34, doi: 10.1016/j.bpg.2009.12.002 [2] Hassan, Bryan & Zhe (2014) 'Motion management in gastrointestinal cancers', Journal of Gastrointestinal Oncology, 5(3), pp. 223-235, doi: 10.3978/j.issn.2078-6891.2014.028