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. 2021 Oct;22(10):315-319.
doi: 10.1002/acm2.13372. Epub 2021 Aug 25.

Dosimetric impact of edema on inguinal lymph node boost in locally advanced vulvar cancer

Sandy Mohamed  1 , Lars Fokdal  2 , Marianne S Assenholt  3 , Jesper Kallehauge  4 , Jacob C Lindegaard  2 , Kari Tanderup  5
Affiliations

Dosimetric impact of edema on inguinal lymph node boost in locally advanced vulvar cancer

Sandy Mohamed et al. J Appl Clin Med Phys. 2021 Oct.

Abstract

We aimed to evaluate the extent of groin edema and its dosimetric effect in boosted inguinal lymph nodes (LN) for vulvar cancer patients. The level of edema was determined in 10 patients treated with radical radiotherapy. A dosimetric evaluation of six LNs in the patient with the maximum level of edema was performed. The accumulated dose across CBCT fractions was acceptable for all six LNs (>94% of prescribed dose) even with the development of up to 13 mm of edema. The major contributor to fractional dose degradation was geographical displacement of the nodes. We suggest evaluation of edema on daily CBCT.

Keywords: VMAT; cancer vulva; daily CBCT; groin edema; image guided radiotherapy; inguinal lymph node boost.

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Figures

FIGURE 1
FIGURE 1
Transverse section of CBCT of fraction number 28 for the presented patient. The outer surface contour is the CBCT contour. The interrupted contour is the planning CT (pCT) body contour. The developed edema is 11 mm on the right inguinal side (difference between pCT and CBCT contours). Red and yellow contours are GTV‐N on CBCT and pCT, respectively. The geographical shift of this LN from pCT to CBCT (center of mass) (“r”) was 10 mm. The depth of this LN from the skin was 9 mm on this CBCT
FIGURE 2
FIGURE 2
The progression of groin edema (D) measured in mm (y‐axis) for the patient who developed maximum level of edema, for right groin represented by the upper line and left groin represented by the lower line. The x‐axis shows the number of the corresponding CBCT
FIGURE 3
FIGURE 3
Relation between the edema (D) measured in mm on the x‐axis, and difference between the delivered and the pCT CTV D98% in % for the 10 mmPTV plan, on the y‐axis. With grouping according to the depth of LN on CBCT measured from skin to the LN (d) in mm where the diamond d = 1–2 mm, the square d = 3–7 mm, and the triangle d = 8–20 mm. r = the geographical shift of the LNs from pCT to CBCT (center of mass) is indicated for LNs with dose reduction of more than 4%
FIGURE 4
FIGURE 4
The delivered D98% (y axis) along the course of the treatment (the evaluated CBCTs), for the 5 mm ptv plan for the included six lymph nodes (LN), three on the left inguinal region (LT 1, 2, 3), and three on the right (RT 1,2,3). The x axis shows the dose in Gy of the corresponding CBCT
See this image and copyright information in PMC

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