Organ motion in pediatric high‐risk neuroblastoma patients using four‐dimensional computed tomography

Abstract

Purpose/objective(s)High‐risk neuroblastoma (HR‐NBL) requires multimodality treatment, including external beam radiation of the primary tumor site following resection. Radiotherapy planning must take into account motion of the target and adjacent normal anatomy, both of which are poorly understood in the pediatric population, and which may differ significantly from those in adults.Methods/materialsWe examined 4DCT scans of 15 consecutive pediatric patients treated for HR‐NBL, most with tumors in the abdominal cavity. The diaphragm and organs at risk were contoured at full inhale, full exhale, and on free‐breathing scans. Maximum displacement of organs between full inhale and full exhale was measured in the anterior, posterior, superior, inferior, left, and right directions, as was displacement of centroids in the A/P, S/I, and L/R axes. Contours on free‐breathing scans were compared to those on 4D scans.ResultsMaximum displacement was along the S/I axis, with the superior aspects of organs moving more than the inferior, implying organ compression with respiration. Liver and spleen exhibited the largest motion, which correlated strongly with the S/I motion of the diaphragm. The maximum organ motion observed in the abdomen and thorax were 4.5 mm and 7.4 mm, respectively, while maximum diaphragm displacement was 5.7 mm. Overall findings mirrored observations in adults, but with smaller magnitudes, as expected. No consistent margins could be added to the free‐breathing scans to encompass the motion determined using 4DCT.ConclusionsOrgan motion within the pediatric abdomen and pelvis is similar to that observed in adults, but with smaller magnitude. Precise margins to accommodate motion are patient‐specific, underscoring the need for 4DCT scanning when possible.

Evaluation of Diaphragm Position Variations During Proton Therapy for Pediatric Patients With Neuroblastoma

“…Pai Panandiker et al have reported an average of 5.1 mm (range: 3.0-10.0), although the distinction between the left and right was not specified [ 6 ]. Kannan et al have reported 4.4 ± 2.0 mm on the right and 3.6 ± 2.3 mm on the left [ 8 ]. Uh et al examined 35 cases and summarized the results in detail for each case [ 9 ].…”

“…Several reports of pediatric respiratory-induced position variations in NBL have been presented [4][5][6][7][8][9][10][11][12][13]. However, reports were limited to four facilities; of these, only one facility reported from Asia, and it is hard to say that a global consensus has been reached regarding the setting of internal margin.…”

“…However, reports were limited to four facilities; of these, only one facility reported from Asia, and it is hard to say that a global consensus has been reached regarding the setting of internal margin. Of the 11 reports on measures for pediatric respiratory-induced position variations mentioned above [4][5][6][7][8][9][10][11][12][13]16], only three reports comprehensively analyzed both intrafractional and interfractional position variations [10,13,16]. Moreover, among these reports, only seven cases were under five years old at the maximum, and the fact is that information on very small children is still lacking.…”

“…Moreover, the information on respiratory motion in children, especially for those less than five years of age, is scarce, and the problem of setting an appropriate internal margin still exists. The analysis of internal organ motion in pediatric NBL has been performed [4][5][6][7][8][9][10][11][12][13], but most reports are from a limited number of institutions, and it is hard to say that there is sufficient consensus about internal organ motion in pediatric patients. Therefore, the intrafractional diaphragm motion and interfractional diaphragm displacement in pediatric patients for NBL have been analyzed to contribute to the accumulation of evidence.…”

Local MRI before and after Tumor Resection in Neuroblastoma: Impact of Residual Disease on Event Free Survival

“…In addition to these general considerations, a recently published study has shown how high the interobserver variability is in determining the operating plan [33]. Over time, radiotherapy techniques have advanced considerably, introducing image-guided, high-precision irradiation, and proton beam therapy to the field of neuroblastomas [34][35][36]. Therefore, exact three-dimensional tumor detection could be increasingly relevant for high-precision irradiations of neuroblastomas as it had already occurred in CNS disease [37,38].…”