PMC6757498_01
Contrast-enhanced CT of the abdomen and pelvis demonstrated a 73 mm x 70 mm x 41 mm hypoattenuating retroperitoneal mass in the right paracaval region medial to the right kidney encasing the inferior vena cava.
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On further workup, contrast-enhanced computed tomography (CT) of the abdomen and pelvis demonstrated a 73 mm x 70 mm x 41 mm hypoattenuating retroperitoneal mass in the right paracaval region medial to the right kidney with 180  abutment of the inferior vena cava (Figure 1).
Gadolinium-enhanced MRI demonstrated a multiloculated T2 hyperintense extravertebral chordoma at the level of L2 in the right retroperitoneum that extends medially along the medial aspect of the right psoas muscle.
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Gadolinium-enhanced magnetic resonance imaging (MRI) demonstrated a multiloculated T2-hyperintense extravertebral chordoma at the level of L2 in the right retroperitoneum that extended medially along the medial aspect of the right psoas muscle (Figure 2).
Axial view of the proton (above) and IMRT (below) dose distribution in color wash. CTV (red). Organs-at-risk: duodenum (cyan), large bowel (brown), ipsilateral kidney (magenta), spinal cord (yellow), contralateral kidney (dark blue), and small bowel (light green).
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Given that the CTV was in close proximity to healthy tissue including the duodenum, small bowel, right kidney, spinal cord, and liver, we created comparison plans of spot-scanning PBT versus intensity-modulated radiation therapy (IMRT) (Figure 3). Both kidneys received essentially no radiation with PBT (Table 1 and Figure 3).