13 Head and Neck - Oropharynx

Head and Neck - Oropharynx

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/02/2021

needle is removed and the plastic tube is pulled through the tissue. A second needle is implanted anteriorly into the base of tongue for creating the anterior leg of the loop – therefore distance and position of the needle related to the posterior insertion channel is important. It is advised, at the beginning of the learning curve, to implant both needles first and control the distance and parallelism of thembefore inserting the plastic tube leaders and pulling through the tissue and completing the loop. The ideal distance apart of the two legs is 25 mm. Less distance results in frequent kinking of the loop. The two or three other sagittal loops are implanted with the same method, paying great attention to keeping them parallel. It is important to keep both legs at least 10 cm distance over the skin surface in order to be able to use the second leg after opening it as a single channel if the loop kinks. Less than 10 cm distance makes the connection to the transfer tubes of the HDR/ PDR machine very difficult. Finally, the loops are secured with plastic buttons to the skin. When large tumours are implanted, the separation between the branches of the loops may exceed 25 mm in order to encompass the entire lesion. If the distance exceeds 30 mm, crossing loops (latero-lateral loops, perpendicular to the sagittal ones) need to be implanted to avoid underdosage between the legs of the loop. To prevent underdosage in the central area of the PTV, crossing frontal loops may be added, with their branches equidistant to those of the sagittal loops. The bridges of the frontal crossing loops are not activated to avoid dose hotspots (Figure 8). Non Looping loop technique [31] A hollow needle (12 gauge) is inserted in the upper neck. This is guided through one finger which is inside the mouth and palpating the base of tongue. The needle is pushed in the posterior and superior direction until it comes out of the base of tongue. Multiple needles are inserted parallel to each other in the sagittal plane until the target is covered (Figure 9). Afterloading catheters with one end sealed are inserted in all the needles. Outside the mouth silk thread is attached to each catheter. This is used for attaching the tubes to the non-looping loop catheter. The needles in the neck are withdrawn and the tubes are pulled from the neck carefully until the crossing catheter sits on the base of tongue. The tubes are well secured in the neck with plastic buttons. The non-looping loop may be allowed to protrude out from the mouth. Multiple such sagittal planes are made so as to cover the target adequately.

Modified Non Looping loop technique with beads [32] Generally the most central and posterior needle is inserted first. The needle is inserted perpendicular to the skin and is guided by bimanual palpation. The sharp end of the needle is guided into the vallecula and is brought into the oropharyngeal air cavity. A plastic tube with thin ends on both sides is taken. One of the thin ends is inserted inside the needle. The needle is pulled out from the neck so that one end of the tube is brought out through the neck. The other end of the tube comes out through the mouth. A second needle is inserted 10-15mm anterior to the first needle.This needle is brought out into the oropharyngeal air cavity. A tube with a bead with at one end and thin segment at the other end is used for this needle. The bead which is attached to the plastic tube has a central hole. The thin end of the tube is inserted into the needle till it comes out in the neck. The needle is then pulled out so that the thick end of the tube comes out. The thin end of the loop tube is now passed through the hole of the bead of the second tube. This tube is now pulled slowly till the bead sits on the base of the tongue. The first loop tube gets anchored to the second tube by this procedure. The third tube is inserted anterior to the second tube keeping 10-15mm distance and the same procedure is repeated. Multiple needles are used until the target volume is covered. By doing this the loop tube gets anchored into the bead (straight) tubes forming a crossing tube. The loop tube with its thin edge is still coming out from the mouth. The tube is cut at the thick end and another tube with a button at the end is inserted into this tube. The tube is then pulled from the neck by a railroad method so that the button tube replaces the loop tube. This forms the first plane. Three or 4 such planes are inserted to cover the target (Figure 10, 11,12). In practice it may be better to place all the most posterior needles (forming loop) of 3-4 planes first. The implant is done posterior to anterior rather than plane by plane as tongue movement becomes restricted after insertion of all needles in one plane. Silk threads are tied at the closed ends of the beads and button tubes, brought out through the mouth and well secured outside on the cheek with tape. These threads are useful for removal of the implant. Modified Non Looping loop technique with sutures [33] In this technique instead of using bead tubes, button tubes are used as straight tubes. These are anchored to the loop tubes with stitches (Figure 13).

Figure 8: Classic Loop technique of brachytherapy for the base of tongue cancer (with courtesy to M Pernot)

Figure 9: Non -looping loop technique for base of tongue cancer ( Bhadrasain et al) [31]