Radiotherapy for gastric mucosa-associated lymphoid tissue lymphoma: dosimetric comparison and risk assessment of solid secondary cancer.
OBJECTIVE
To determine the optimal radiotherapy technique for gastric mucosa-associated lymphoid tissue lymphoma (MALToma), we compared the dosimetric parameters and the risk of solid secondary cancer from scattered doses among anterior-posterior/posterior-anterior parallel-opposed fields (AP/PA), anterior, posterior, right, and left lateral fields (4_field), 3-dimensional conformal radiotherapy (3D-CRT) using noncoplanar beams, and intensity-modulated radiotherapy composed of 7 coplanar beams (IMRT_co) and 7 coplanar and noncoplanar beams (IMRT_non).


METHODS
We retrospectively generated 5 planning techniques for 5 patients with gastric MALToma. Homogeneity index (HI), conformity index (CI), and mean doses of the kidney and liver were calculated from the dose-volume histograms. Applied the Biological Effects of Ionizing Radiation VII report to scattered doses, the lifetime attributable risk (LAR) was calculated to estimate the risk of solid secondary cancer.


RESULTS
The best value of CI was obtained with IMRT, although the HI varied among patients. The mean kidney dose was the highest with AP/PA, followed by 4_field, 3D-CRT, IMRT_co, and IMRT_non. On the other hand, the mean liver dose was the highest with 4_field and the lowest with AP/PA. Compared with 4_field, the LAR for 3D-CRT decreased except the lungs, and the LAR for IMRT_co and IMRT_non increased except the lungs. However, the absolute differences were much lower than <1%.


CONCLUSIONS
Tailored RT techniques seem to be beneficial because it could achieve adjacent organ sparing with very small and clinically irrelevant increase of secondary solid cancer risk compared to the conventional techniques.
Department of Radiation Oncology, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.|Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Sun Hyun
SH
Bae
Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
Dong Wook
DW
Kim
Department of Radiation Oncology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea.
Mi-Sook
MS
Kim
Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea.
Myung-Hee
MH
Shin
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Hee Chul
HC
Park
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Do Hoon
DH
Lim
Mucosa associated lymphoid tissue lymphoma; Radiotherapy; Secondary cancer risk; Stomach; Treatment planning