|Ahead of print publication
MRI-guided stereotactic ablative radiation therapy for liver metastasis from pancreatic cancer
Yukihiro Hama, Etsuko Tate
Department of Radiation Oncology, Tokyo-Edogawa Cancer Centre, Edogawa Hospital, Tokyo, Japan
|Date of Submission||01-Aug-2020|
|Date of Decision||28-Sep-2020|
|Date of Acceptance||18-Dec-2020|
|Date of Web Publication||03-Nov-2021|
Department of Radiation Oncology, Tokyo-Edogawa Cancer Centre, Edogawa Hospital, 2-24-18 Higashikoiwa, Edogawa, Tokyo, 133-0052
Source of Support: None, Conflict of Interest: None
A 69-year-old man with a history of pancreatic cancer was referred to our hospital for a newly developed solitary liver metastasis. Since the liver metastasis was in contact with the small intestine, it was necessary to perform radiation therapy while simultaneously monitoring the small intestine and liver metastasis, and then, MRI-guided stereotactic ablative radiation therapy (SABR) was performed. There were no radiation-induced adverse events during the treatment and 6 months of follow-up. MRI showed complete regression of the tumor at 6 months after SABR. It seems feasible to perform SABR safely by using MRI-guided radiation therapy system even if liver metastasis developed near the intestinal tract after surgery for pancreatic cancer.
Keywords: Image-guided radiation therapy, liver neoplasms, oligometastasis, pancreas, stereotactic body radiation therapy
| > Introduction|| |
On-board real-time MRI-guided radiation therapy (MRgRT) is considered to improve overall survival of inoperable pancreatic cancer; however, its efficacy and safety for liver metastasis have not been thoroughly investigated. MRgRT can deliver a high dose of radiation to the liver metastasis while sparing the surrounding organs at risk without fiducial placement. Chemotherapy with or without targeted therapy is recommended for patients who have developed liver metastasis after surgery for pancreatic cancer, but the prognosis remains dismal and adverse events cannot be overlooked. Here, we report a case of solitary liver metastasis that developed near the small intestine after resection of pancreatic cancer, which was successfully treated with MRgRT. As far as we know, this is the first well-documented report of MRgRT for liver metastasis from pancreatic cancer which is located in contact with the intestine.
| > Case Report|| |
A 69-year-old man was referred to our hospital for the treatment of liver metastases from pancreatic cancer. The patient underwent definitive surgery for Stage IIA resectable pancreatic adenocarcinoma 2 years previously and received adjuvant chemotherapy composed of TS-1 for 6 months. The posttreatment course was uneventful; however, follow-up computed tomographic (CT) scans revealed a solitary liver metastasis 18 months after the adjuvant chemotherapy. No recurrent lesions other than liver metastasis were detected on whole-body contrast-enhanced CT scans. The patient was initially supposed to receive chemotherapy but refused, so he decided to undergo stereotactic ablative radiation therapy (SABR). Contrast-enhanced CT scans showed a solitary metastasis in the segment 4 of the liver, but it was in contact with the small intestine [Figure 1]a and [Figure 1]b. T2-weighted fast spin-echo imaging showed a well-demarcated hyperintense mass, and sagittal true fast imaging with steady precession (FISP) showed that the lesion was in contact with the small intestine, but it was not considered as direct invasion from the liver metastasis [Figure 1]c and [Figure 1]d. Since there was concern about radiation damage to the small intestine due to respiratory motion and peristalsis, SABR was performed using the tri-60Co MRgRT system (MRidian, ViewRay, OH, USA).
|Figure 1: (a) Axial contrast-enhanced computed tomographic scan showing a well-defined oval lesion in the segment 4 of the liver (arrow). (b) Sagittal contrast-enhanced computed tomographic scan showing that the lesion is in contact with the small intestine (arrow). (c) Axial T2-weighted fast spin-echo imaging showing a well demarcated hyperintense mass (arrow). (d) Sagittal true fast imaging with steady precession image showing that the lesion (arrow) was in contact with the small intestine, but it was not considered as direct invasion|
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All procedures were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. This study was approved by the institutional review board, and written informed consent was obtained from the patient. The patient underwent MRI simulation on MRgRT system with surface coils on the abdomen using true FISP images. Fusion images of contrast-enhanced CT and true FISP MRI were generated using Monaco 5.0 treatment planning software (Elekta AB, Stockholm, Sweden), and gross tumor volume (GTV) was defined on true FISP MRI. Planning target volume (PTV) was defined as 0.5–1 mm margin expansion from GTV on true FISP MRI. The prescribed dose to the dose covering 95% of the PTV was 40 Gy in 8 fractions over 10 days [Figure 2]. Tri-Co-60 step-and-shoot intensity-modulated radiotherapy plan was generated. The maximum dose within PTV was not constrained. We strived to keep his D1cc of the small intestine to <39 Gy. The MRgRT allowed us to image the treatment area and deliver radiation at the same time. There were no radiation-induced adverse events during the MRgRT and 6 months of follow-up. Follow-up MRI showed complete regression of the tumor at 6 months after MRgRT [Figure 3]a and [Figure 3]b.
|Figure 2: MRI-guided stereotactic ablative radiation therapy isodose line distribution. Isodose lines are displayed on (a) axial and (b) sagittal true fast imaging with steady precession images. Isodose lines with corresponding actual radiation dose were given over 8 fractions|
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|Figure 3: (a) Axial T2-weighted fast spin-echo imaging showing complete regression of the tumor (arrow). (b) Sagittal true fast imaging with steady precession image showing that the lesion (arrow) disappeared|
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| > Discussion|| |
Multiagent chemotherapy with or without targeted therapy is usually performed for patients with recurrent pancreatic cancer after surgical resection., However, chemotherapy is not always recommended for all patients because of its low response rate and significant adverse events., The patient refused multiagent chemotherapy, and SABR was considered because his recurrent lesion was oligometastasis in the liver. Radical local treatment for oligometastasis, including SBRT, has been shown to prolong disease-free survival and overall survival in some cancer types;, however, little is known about pancreatic cancer.
The advantages of MRgRT for liver metastasis are noninvasive motion monitoring, providing greater soft tissue contrast than CT, and requiring no additional radiation dose to the patient. These advantages are useful in performing radical local treatment for liver metastasis that developed near the intestinal tract. In this case, by monitoring respiratory motion and peristalsis of the intestine during SABR, we could irradiate the liver metastasis accurately while suppressing radiation exposure to the surrounding intestinal tract.
There are several limitations in this study. First, MRI shows superior soft tissue contrast as compared to diagnostic CT or cone-beam CT (CBCT), but the spatial resolution of MRI is lower than CT or CBCT. Therefore, it is necessary to avoid accidental overdose irradiation to the intestinal tract. We tried to average out the radiation exposure to the intestinal tract by increasing the number of fractionations. Second, this is a single case report and the findings of this case cannot be generalized to others without further scientific verification. However, this case suggested that radical local treatment can be safely performed even if liver metastasis develops near the intestinal tract after surgery for pancreatic cancer.
In conclusion, it was considered feasible to perform SABR safely by using MRgRT system even if liver metastasis developed near the intestinal tract after surgery for pancreatic cancer.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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