|Year : 2015 | Volume
| Issue : 3 | Page : 575-579
Study of distribution of inguinal nodes around the femoral vessels and contouring of inguinal nodes
Arpitha S Rao, Karthick Rajmanickam, Geeta S Narayanan
Department of Radiotherapy, Vydehi Institute of Medical Sciences and Research Centre, Bengaluru, Karnataka, India
|Date of Web Publication||9-Oct-2015|
Arpitha S Rao
Vydehi Institute of Medical Sciences and Research Centre, #82, EPIP Area, Whitefield, Bengaluru - 560 066, Karnataka
Source of Support: None, Conflict of Interest: None
Aims: To determine the distribution of inguinal nodes around the vessels, margins needed around the vessels and inferior extent of contouring in the inguinal region.
Subjects and Methods: Fifty patients having pelvic malignancies with one or more malignant nodes in the inguinal region were retrospectively included in this study. The position of the nodes in relation to the vessels, size of the nodes, the distance from the center of the node to the edge of the nearest vessel was measured. Margins required to cover the nodes from the vessels and position of the nodes in relation to the lesser trochanter was noted.
Results: Most of the nodes were placed either anteromedial (46%) or anterior (46.6%) to the vessels (92.6%). The range of margin required to cover all nodes in the anteromedial, anterior and anteriolateral direction varied from 0.8 to 2.7 cm. Only one node was more than 2 cm below the lower edge of lesser trochanter.
Conclusion: Elective clinical target volume for inguinal lymph nodes requires a minimum margin of 2.5 cm from the femoral vessels in the anterior, anterolateral and anteromedial direction 1.5 cm margin is required medially. Inferior extent of the contour should be 2 cm below the lower edge of lesser trochanter.
Keywords: Contouring, femoral vessels, inguinal nodes, lesser trochanter, margins, pelvic malignancies
|How to cite this article:|
Rao AS, Rajmanickam K, Narayanan GS. Study of distribution of inguinal nodes around the femoral vessels and contouring of inguinal nodes. J Can Res Ther 2015;11:575-9
|How to cite this URL:|
Rao AS, Rajmanickam K, Narayanan GS. Study of distribution of inguinal nodes around the femoral vessels and contouring of inguinal nodes. J Can Res Ther [serial online] 2015 [cited 2019 Nov 14];11:575-9. Available from: http://www.cancerjournal.net/text.asp?2015/11/3/575/163735
| > Introduction|| |
Radiation target volumes will include the inguinal nodal region for malignancies such as anal canal cancers, vulval cancers, carcinoma cervix involving the lower vagina, carcinoma of vagina, carcinoma penis and carcinoma urethra, either to cover microscopic nodal metastases or overt lymph node involvement. Four-field techniques defined by bony landmarks are being replaced by intensity modulated radiation therapy (IMRT) for the treatment of pelvic malignancies. Role of IMRT in the treatment of anal cancer and vulvar cancer has been investigated in various studies and has demonstrated reduced radiation doses to organs at risk, that is, the bowel, bladder, genitalia, femoral heads, and bone marrow. ,,, But, these studies have not focused on contouring the inguinal nodal region.
The Radiation Therapy Oncology Group Contouring atlas for conformal radiotherapy in anorectal cancer  also lacks description of contouring of inguinal nodal region. Hence, there is an opportunity to describe in detail the contouring of inguinal nodal region.
The purpose of this study was to determine the anatomical distribution of inguinal nodes around the vessels, margins needed around the vessels and to determine the inferior extent of contouring in the inguinal region.
| > Subjects and methods|| |
Between August 2013 and August 2014, all patients with biopsy proven primary carcinomas originating in the pelvis with known primary drainage to inguinal nodes were retrospectively analyzed. Being a retrospective study, fine-needle aspiration cytology/positron emission tomography/biopsy of the lymph nodes could not be done to confirm the malignancy of the lymph node. All patients had undergone planning computed tomography (CT) scan with contrast in supine position with 5 mm slice interval and these were used for this study. Patients with one or more malignant nodes in the inguinal region with the following radiological criteria were included in the study.
Most widely used CT criterion to determine if a node is benign or malignant, is the nodal size. The short axis diameter of a lymph node was measured as it has been demonstrated that this is constant, despite orientation because the node is likely to become rounder before it elongates. The short axis diameter is measured perpendicular to the longest diameter of the lymph node. , Lymph nodes measuring more than 1 cm in the short axis diameter are considered malignant in the inguinal region. , Since the sensitivity of this method is only 40-70%, ,, only lymph node size is not a reliable parameter for the evaluation of metastatic involvement. Other factors like shape, contour, heterogeneous contrast enhancements, etc., were also taken into consideration. Malignant nodes have irregular borders due to extra capsular extension and are heterogeneous on contrast enhancement. 
Patients having >1 nodes with a short axis diameter of >10 mm and also having one or more other malignant radiological features were included for the study. The other enlarged nodes in these patients which do not fulfill the above size criteria may still contain tumor deposits, as 10-20% of normal sized nodes may contain tumor deposits.  Therefore while analyzing the clinical target volumes (CTVs), all enlarged nodes in these patients were taken into consideration.
A total of 50 patients were included in this study. Among them were 40 cases of cervical cancers with lower vaginal involvement, six cases of carcinoma rectum with anal canal involvement, one case of carcinoma bladder with urethral involvement, one case of carcinoma penis, one case of carcinoma vulva, and one case of carcinoma of anal canal. All the enlarged inguinal lymph nodes in the above mentioned patients were contoured using the Eclipse Planning System version 11.1 (Varian Medical Systems, Palo Alto, CA, USA) on the planning CT with contrast.
The following parameters were assessed:
- Position in relation to the vessels - To assess the position of the nodes in relation to the vessels, nine imaginary quadrants were created as shown in [Figure 1] with the help of two vertical and two horizontal lines. With the vessels in the central quadrant, eight quadrants around the vessels were as follows: Anterior, anteromedial, anterolateral, medial, lateral, posterior, posteriolateral, and posteriomedial. Based on these quadrants, nodal position was noted
- Size of the nodes - Both the long axis diameter and the short axis diameter were noted
- Distance of the nodes from the vessels - The distance from the center of the positive node(s) to the edge of the nearest vessel was measured
- Margins required to cover the nodes from the vessels - The vessels were contoured. Serially bigger margins in the required directions were applied and the least margins required to cover the nodes were noted. Margins required acquiring 95% of nodal coverage is noted
- Position of the nodes in relation to lesser trochanter - To assess the inferior extent of the contouring, the position of the nodes in relation to inferior edge of the lesser trochanter was noted.
|Figure 1: Contrast enhanced computed tomography scan image showing femoral vessels. Eight imaginary quadrants around the vessels. A = Anterior, P = Posterior, M = Medial, L = Lateral, AM = Anteriomedial, AL = Anteriolateral, PM = Osteriomedial, PL = Posteriolateral|
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| > Results|| |
A total of 50 patients were included in this study. Among the 50 patients, 40 patients had bilateral inguinal lymphadenopathy and 10 had unilateral lymphadenopathy. A total of 150 inguinal lymph nodes were analyzed.
Position of the nodes
In relation to the vessels, the quadrant to which the nodes belonged to was noted. Some nodes extended to two quadrants and the quadrant to which it predominantly belonged to are mentioned first. 28% (42) of the nodes were in the anteromedial quadrant, 17.3% (26) were in the anteromedial and anterior quadrant and 0.6% (1) nodes were in anteromedial and medial quadrant, that is, around 46% (69) of nodes were predominantly in anteromedial quadrant. 24% (36) of the nodes were in the anterior quadrant, 17.3% (26) were in the anterior and anteromedial quadrant, 5.3% (8) were in anterior and anterolateral quadrant, that is, a total of 46.6% (70) nodes predominantly were placed anterior to the vessels. 2% (3) were anterolateral and 3.3% (5) were in anterolateral and lateral quadrant, that is, a total of 5.3% (8) of the nodes were predominantly anterolateral to the vessels. 2% (3) were in the medial quadrant. No nodes were found posterior to the vessels.
The size of the nodes (short axis diameter) ranged from 0.5 to 2.5 cm. The range of the size and mean size, quadrant wise is shown in [Table 1].
|Table 1: The number of nodes in each quadrant, range of size and mean short axis diameter|
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Distance from the vessels and margins required
The range of the distance of center of the node to the edge of the nearest vessels and the margins required to cover them is shown in [Table 2].
|Table 2: Range of distance of the nodes from the vessels, mean distance, margins required to cover the nodes, the mean margin and margins required to cover 90% and 95% of the nodes|
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Position of the nodes in relation to lesser trochanter
Lower limit of 38 nodes reached the lower border of lesser trochanter. Sixteen of them were 0.5 cm below, 5 nodes were 1 cm below, 6 nodes were 1.5 cm below and only one node was more than 2 cm below the lower limit of lesser trochanter. Rests of the nodes were above the lesser trochanter. This is shown in [Table 3].
|Table 3: Range of distance of the nodes from the lesser trochanter, the mean distance and the inferior margin to contour the 95% of the nodes|
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| > Discussion|| |
Implementation of IMRT requires a detailed understanding of the anatomy. Inguinal nodal radiation will be required in the treatment of many pelvic malignancies. Hence, a detailed knowledge of distribution of the inguinal nodes in relation to the vessels is required.
The Radiation Therapy Oncology Group Contouring atlas for elective clinical target volumes for conformal radiotherapy in anorectal cancer recommends that for pelvic nodes, a 7- to 8-mm margin around the vessels is required. The group also recommends the caudal extent of the inguinal region to be 2 cm caudal to the sapheno-femoral junction. However, description of circumferential margin around the vessels has not been mentioned. Lower edge of the ischial tuberosities is recommended by the Australian Gastrointestinal Trial group for the caudal extent of inguinal region contouring.  Kim et al.  in their study to determine the optimal margins needed around the femoral vessels studied 22 patients with pelvic malignancies. They concluded that >2 cm margin is required in most directions around the femoral vessels but did not describe the inferior extent of the inguinal nodal region. Other studies investigating the benefits of IMRT in pelvic malignancies have focused on dose reduction to organ at risk. There are no clear guidelines with respect to contouring the inguinal nodal region. Extrapolating the pelvic region guidelines to the inguinal region may be inadequate to cover all the nodes.
We studied 50 patients with pelvic malignancies and positive inguinal nodes. The distribution of 150 inguinal nodes around the vessels was studied and the information is being extrapolated to define the CTV required in the inguinal region.
Our findings suggests that most of the nodes were placed either anteromedial (46%) or anterior (46.6%) to the nodes (a total of 92.6%). Few nodes were anterolateral (5.3%) and medial (2%) to the vessels. We did not find any nodes placed posterior to the vessels.
The range of distance of the center of the nodes from the nearest vessels in the anteromedial direction varied from 0.6 to 2 cm and the range of margin varied from 1 to 2.6 cm to cover all the nodes. Margin required to cover 95% of the nodes is 2.50 cm. Hence, a minimum margin of 2.5 cm is needed along the anteromedial direction to cover all the nodes.
In the anterior direction, the range of center of the nodes from the vessels in anterior direction varied from 0.5 to 2.2 cm and the range of margin varied from 0.8 to 2.7 cm to cover all the nodes. Margin required to cover 95% of the nodes is 2.25 cm. Hence, a minimum margin of around 2.5 cm is required in the anterior direction.
In the anterolateral direction, the range of distance from center of the nodes to the vessels varied from 0.78 to 2 cm and the range of margin varied from 1.2 to 2.7 cm to cover all the nodes. Margin required to cover 95% of the nodes is 2.70 cm. Hence, a margin of around 2.5-3 cm is required in the anteriolateral direction. Australian group has recommended the lateral margin to be medial margin of iliopsoas or sartorius. In our study, we found that lateral extent of thrIn the medial direction, the range of center of the nodes to the vessels varied from 0.6 to 0.76 cm and the margins varied from 0.9 to 1.5 cm. Margin required to cover 95% of the nodes is 1.5 cm. Hence, a minimum margin of 1.5 cm medially is adequate to cover all the nodes. No margin is required in the posterior direction. Based on these recommendations, the CTV N contouring for the inguinal nodes is depicted in [Figure 2].
|Figure 2: Contrast enhanced computed tomography scan image depicting the clinical target volume in the inguinal region. FV = Femoral vessels, FA = Femoral artery, BP = Bony pelvis|
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There is no consensus regarding the lower limit of contouring. In our study we found that among the 150 nodes only six nodes were 1.5 cm below the lower edge of lesser trochanter and only one node was more than 2 cm below the lower edge of lesser trochanter. Inferior extent of the contour to cover 95% of the nodes is 1.5 cm. Hence, we recommend to contour until 2 cm below the lower edge of lesser trochanter when treating electively and to include any nodes below if any [Figure 3].
|Figure 3: Digitally reconstructed radiograph image showing the lower extent of elective clinical target volume of inguinal nodal region|
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To summarize, our recommendations would be to use a combination of bony landmark-based boundaries and margins which are as follows:
Cranial : The level where the external iliac artery leaves the bony pelvis to become the femoral artery.
Caudal : 2 cm below the lower edge of lesser trochanter [Figure 3].
Anterior : A margin of 2.5 cm from the femoral vessels, inclusive of any visible lymph nodes.
Posterior : No margin is required around the vessels.
Lateral : The medial edge of iliopsoas muscle.
Medial : A margin of 1.5 cm from the femoral vessels.
Anteromedially : A margin of 2.5 cm or inclusive of any visible nodes.
Anterolaterally : A margin of 2.5-3 cm or inclusive of any visible nodes.
| > Conclusion|| |
Clinical target volumes for inguinal nodal region require a minimum margin of 2.5 cm from the femoral vessels in most directions, except medially (1.5 cm) and posteriorly (no margin). Caudal extent of contouring should extent until 2 cm below the lower edge of lesser trochanter during elective treatment.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]