Fig. 12.1
Representative contours for postoperative external beam radiotherapy of a pT2N1M0 stage IIIB adenocarcinoma of the gallbladder. Representative axial (a) and coronal (b) sections of the tumor bed ITV as well as the PTV volumes receiving 4500 and 5400 cGy. Tumor bed ITV was generated based on 4D-CT images. Representative contours of the celiac axis (c) and superior mesenteric artery (d) expansions that comprise the PTV receiving 4500 cGy. Representative contours of the pancreaticoduodenal (e) and porta hepatis (f) lymph node regions that also comprise the PTV receiving 4500 cGy
Fig. 12.2
Representative contours for definitive external beam radiotherapy of a cT2bN1M0 stage IIIB hilar cholangiocarcinoma with positive surgical margins. Representative axial (a) section of the primary tumor ITV as well as the PTV for the 4500 cGy dose level. Tumor ITV was generated based on 4D-CT images. (b) Axial section of PET scan with overlay of PTV for the 4500 cGy dose level. (c) Representative contours of the celiac axis (c) and superior mesenteric artery (d) expansions that comprise the PTV for the 4500 cGy dose level. (e) Representative contours of the porta hepatis lymph node region that comprises the PTV receiving 4500 cGy. (f) Coronal section with overlays of the PTV for 4500 and 5400 cGy dose levels
The surgical bed is best defined by careful examination of the operative report and may be highlighted on imaging by radiopaque clips or staples left by the surgeon. Normal anatomic relationships may be disrupted postoperatively. Careful study of the preoperative scans and detailed discussion with the surgeon are critical.
For hilar cholangiocarcinoma, surgery requires resection of the involved extrahepatic biliary structures and adjacent hepatic parenchyma, as well as a biliary-enteric anastomosis (choledocho- or hepatico-jejunostomy). Thus, the surgical bed tracks along the medial aspect of the remaining liver, within a reasonable radius around surgical clips, and includes the surgical anastomosis.
For distal extrahepatic cholangiocarcinoma, resection involves the involved extrahepatic biliary ducts, with or without a pancreaticoduodenectomy and biliary-enteric anastomosis. The postoperative bed is centered on the new anastomosis between the biliary tree and small bowel and guided by surgical clips.
For gallbladder cancer, surgery requires radical or extended cholecystectomy, which involves resection of a margin of hepatic tissue around the gallbladder. This relates to the tendency of gallbladder cancers to infiltrate through Rokitansky-Aschoff sinuses and the gallbladder wall into adjacent hepatic tissue. Thus, the tumor bed includes a rim of hepatic tissue in the space previously occupied by the gallbladder (as indicated by surgical clips, see Fig. 12.1a, b).
The pattern of lymphatic drainage for extrahepatic and hilar cholangiocarcinomas has been described in a study using blue dye technique [1].
The first site of drainage is the pericholedochal lymph node station. The lymphatic drainage then descends either along the portal vein into the surrounding nodes, along the common hepatic artery into the surrounding nodes, or along the biliary tree to the pancreaticoduodenal node station.
Notably, lymph flow does not ascend toward the hepatic hilum. The tertiary nodal stations include the nodes surrounding the celiac axis and superior mesenteric artery as well as the aortocaval nodes.
This lymphatic flow pattern is supported by clinical studies. In a study by Kitagawa et al., 110 patients underwent lymph node dissection in addition to surgical resection, of which 52 % of patients had nodal disease [2]. The pericholedochal lymph node group was the most frequent site of lymph node metastasis (42 %), followed by the nodes along the portal vein (31 %), nodes along the common hepatic artery (27 %), and the pancreaticoduodenal nodes (15 %).
12.3 Simulation (Including Motion Management, IGRT)
CT simulation with intravenous and oral contrast.
Arms up in shuttle board, partial body vacuum-lock bag for immobilization.
4D-CT to evaluate target motion and creation of internal target volume (ITV).
If gross disease is suspected, consider MRI simulation or fusion with MRI images for target delineation.
For treatment, use daily orthogonal kV images for IGRT, with weekly cone beam CT to evaluate target coverage and bowel/target interface changes.
12.4 Dose
General external beam radiation therapy dose guidelines:
Gross disease with margin for microscopic extension and daily setup variation treated with 54 Gy to 64.8 Gy in 1.8 Gy per fraction respecting tolerance of organs at risk.
Postoperative bed treated with 50.4 to 59.4 Gy in 1.8 Gy per fraction, with consideration to margin status and organs at risk.
At-risk nodal stations treated to 45 Gy in 1.8 Gy per fraction.
Intensity-modulated radiotherapy (IMRT) technique can be considered to spare organs at risk (see Fig. 12.3a–c).
Fig. 12.3
Dose distribution of external beam radiation for postoperative treatment of extrahepatic cholangiocarcinoma, using 3D-conformal technique with four fields (a) and intensity-modulated radiotherapy (IMRT) (b). Dose range shown is 25 Gy (blue) to 64 Gy (red). In (c), dose volume histogram shows sparing of the liver and small bowel with IMRT (Previously published in: Kalbasi and Ben-Josef [26])
There is limited data to guide dose selection in radiation therapy of cancers of the gallbladder and bile ducts. Most series support radiation doses consistent with other tumors of the gastrointestinal tract because of shared OARs. The use of concurrent chemotherapy should also be considered in dose determination.
For extrahepatic and hilar cholangiocarcinoma, in the adjuvant setting, most studies using external beam radiotherapy alone report median doses ranging from 45 to 54 Gy in 1.8–2.0 Gy per fraction [3–7]. Similar doses were utilized in studies of adjuvant radiation in gallbladder cancers [8–10].
In the unresectable or definitive setting, for typical fractionated radiotherapy, most recent studies have reported similar doses – 45–60 Gy in standard 1.8–2.0 Gy per fraction [4, 10–12]. Given the pattern of failure and the stated goal of delaying progression for as long as possible, a reasonable approach would be to deliver as high a dose as safely possible given the OAR constraints.
12.5 Contours
Please refer to Figs. 12.1a–f and 12.2a–f for this section.
GTV
Any gross residual disease on imaging is the gross tumor volume (GTV) and should be delineated separately.
CTV
Include the GTV with a margin for microscopic extension (~1.0–1.5 cm).
In the adjuvant setting, the postoperative bed and related anastomoses are included in the CTV, which are described in detail in Figure 12.1a and 12.1b.
In the adjuvant setting, the regional lymph nodes are included in the CTV.
Regional lymph nodes for extrahepatic and hilar cholangiocarcinoma thus include the pericholedochal lymph nodes. For hilar cholangiocarcinomas, these nodes are within the hepatic hilum and porta hepatis.
The CTV also extends to a 1 cm margin around the portal vein from the hepatic hilum to its junction with superior mesenteric and splenic veins to include the surrounding nodes.
To encompass the pancreaticoduodenal nodes, the CTV will also include the area surrounding the groove between the pancreatic head and duodenum, and in particular its posterior aspect, with a 0.5–1.0 cm margin.
The celiac trunk and the proximal superior mesenteric artery, also typically with a 1 cm margin, are also within the CTV to include corresponding lymph nodes (similar to RTOG guidelines for postoperative treatment of pancreatic cancer).
For distal extrahepatic cholangiocarcinoma, para-aortic lymph nodes can be included.
For intact extrahepatic cholangiocarcinoma and gallbladder cancer, the regional nodes have typically also been included in the CTV. However, given the patterns of failure (primarily at the site of gross disease or at distant sites), the rationale for this practice is debatable.Related posts:
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