Main Session
Sep
29
PQA 05 - Physics
Presenter(s)
Hatice Kubra Isik, MD - Marmara University Pendik Education and Research Hospital Radiation Oncology Clinic, Istanbul, Marmara
H. K. Isik1, S. B. Kilicer2, T. Tasçi3, and H. Alkis1; 1Department of Radiation Oncology, Marmara University School of Medicine, Istanbul, Turkey, 2Marmara University Pendik Education and Research Hospital Radiation Oncology Clinic, istanbul, Turkey, 3Marmara University Pendik Education and Research Hospital Radiation Oncology Clinic, Istanbul, Turkey
Purpose/Objective(s):
Respiratory motion results in significant displacement of abdominal organs with affecting dose distribution and normal tissue exposure during radiotherapy (RT). Kidneys are clinically critical organs that require protection during RT, particularly in patients with advanced/metastatic cancer at risk of renal toxicity due to prior chemotherapy and/or RT. Majority of the vertebral metastases are nearby the kidneys which are generally located at the level of T11-L4 vertebrae. This study aimed to compare the differences in renal dose parameters with kidney positional changes during free breathing (FB) and deep inspiration breath-hold (DIBH) techniques in RT planning of T12 and L1 vertebrae which are generally located near the superior renal pole.Materials/Methods:
This retrospective study was designed as a dosimetric plan comparison analysis. Patients who had both DIBH and FB simulation images were included. For each patient, separate treatment plans were generated on DIBH and FB image sets. A dose of 800 cGy in a single fraction was prescribed. Renal doses were converted to an equivalent dose corresponding to 1800 cGy based on the 800 cGy/1 fraction scheme. In all patients, the kidneys as well as the T12 and L1 vertebrae were contoured by the same radiation oncologist. Treatment plans were comparatively evaluated under identical planning conditions. Renal mean dose (Dmean) values were analyzed using dose–volume histogram data and compared between DIBH and FB plans. The Wilcoxon signed-rank test was used for statistical analysis.Results:
At the T12 vertebral level (n=10), statistically significant differences were observed between FB and DIBH plans for both kidneys. The right kidney Dmean was significantly lower in DIBH plans compared with FB plans (p=0.007). Similarly, the left kidney Dmean was significantly reduced with DIBH compared to FB (p=0.013).However, at the L1 vertebral level (n=12), no statistically significant difference in Dmean was observed between FB and DIBH plans for either the right kidney (p=0.43) or the left kidney (p=0.69). Mean ± SD of the kidneys Dmean is detailed in the table.Conclusion:
The findings demonstrate that the DIBH technique provides a significant dosimetric advantage in reducing renal dose at the T12 vertebral level, whereas a similar benefit was not observed at the L1 level. These results suggest that the choice between FB and DIBH techniques may be individualized according to metastatic vertebra’s anatomical proximity to the kidneys. Optimizing renal dose during RT may contribute to reducing cumulative renal toxicity, particularly when combined with systemic treatments.| T12 vertebra (n=10) | L1 vertebra (n=12) | |||||
| FB | DIBH | p-value | FB | DIBH | p-value | |
| Right Kidney | 80.22 ± 64.87 | 36.60 ± 26.53 | 0.007 | 141.85 ± 50.04 | 118.68 ± 71.63 | 0.43 |
| Left Kidney | 74.49 ± 39.35 | 51.62 ± 32.28 | 0.013 | 95.17 ± 45.19 | 92.14±50.70 | 0.69 |