32. Keloids - The GEC-ESTRO Handbook of Brachyterapy

Keloids

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 11/04/2025

3. Planning target volume (PTV) covers at least the CTV for interstitial techniques. 4. For mould techniques the PTV includes the CTV and a 0.5 cm position uncertainty margin in all directions. Image based treatment planning is strongly recommended to determine the exact position of the catheter and, adjust the target volume if necessary. In this way, underdosing and hot spots can be avoided. [9, 12].

Simple surgical excision of keloids can result in recurrence rates of 60% to 80% [7, 8]. The recurrence rate for postoperative radiotherapy is significantly lower at an average of 22% which rises to 37% for radiotherapy alone. In a recent metanalysis perioperative brachytherapy showed the lowest recurrence rate of 15%, while X-ray and electron beam treatment have a recurrence rate of 23% [9]. The German guideline for the treatment of pathological scars states a 1.2-2 times higher recurrence rate for external beam radiation techniques compared to brachytherapy [2]. In a meta analysis by Kal et al. different dose concepts were evaluated, the authors found that from a BED of 30Gy the risk of recurrence is less than 10% [10, 11]. Before perioperative brachytherapy, the physical and psychological suffering due to the keloid should be discussed with the patient. Patients should be informed of the possible secondary estimated risk of malignancy (1/50,000) and the risk of recurrence. Because of the effect on tissue growth and possible cancer induction, brachytherapy should not be carried out in children, except in very critical situations where the risk is considered worthwhile. In the published series of adult patients, no increased incidence of cancer induction has been reported until now.

8. TECHNIQUE

The technique for irradiating keloids with brachytherapy was initially described by Nicoletis and Chassagne in 1967 [13]. Plastic tubes are recommended because they adapt easily to curvatures in the scar. The keloid resection and the insertion of the brachytherapy catheter is possible under local anesthesia or general anesthesia. Typically, immediately after keloid excision, a blind end plastic tube should be positioned along the centre of the scar subcutaneously 3-5 mm deep. The scar is then closed with a non-soluble suture. It is necessary that the plastic catheters cover the entire scar length. The catheter should extend 5 mm beyond both ends of the scar for optimal coverage of the PTV. In large excision wounds it is advocated that the wound is closed with subcutaneous sutures to approximate the wound edges before inserting the plastic tube. The surgical skin sutures are usually intradermal, the epidermis is not pierced but closed by adhesive strip. Careful positioning of the plastic tube, avoidance of infection and/or bleeding in the scar is extremely important to prevent recurrences. We recommend therefore as a final step to cover the entire scar with a compression bandage and to leave only one end of the plastic catheter free for connecting to the afterloading machine (Fig 32.3).

7. TUMOUR, TARGET VOLUMES AND ORGANS AT RISK

For interstitial brachytherapy, it is recommended to implant the catheter at a depth of 5 mm. The target volume for interstitial brachytherapy after keloid excision consists of the margins around the excision along the entire surgical scar and a 5 mm safety margin in all directions to capture the relevant fibroblast population. 1. Gross target volume (GTV) includes the whole scar. 2. Clinical target volume (CTV) including the scar and 5mm of the affected skin.

Figure 32.3. Situation during positioning of the catheter 5 mm deep (left picture) and after closure (right picture)