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

TABLE 32.1 LISTS DIFFERENT HDR DOSE SCHEDULES AND FRACTIONATION REGIMENS WITH CORRESPONDING BED AND EQD2 (α/β VALUES OF 10 GY) Fractionation schedule BED 10 EQD2 10 3 x 6 Gy 28.8 Gy 24.0 Gy 4 x 3 Gy 15.6 Gy 13.0 Gy 2 x 7 Gy 23.8 Gy 19.8 Gy 1 x 8 Gy 14.4 Gy 12.0 Gy 3 x 5 Gy 22.5 Gy 18.8 Gy 1 x 13 Gy 29.9 Gy 24.9 Gy 2 x 6 Gy 19.2 Gy 16.0 Gy

Another technique reported by Xiaoping (36) uses a postoperative mould irradiation. Other, less common and seldom used techniques are contact brachytherapy with Sr 90 applicators [14].

In the retrospective analyses by Kal et al. it was calculated that with a BED 10 of more than 30 Gy (25 Gy EQD2 10 ) the recurrence rate would be less than 10 % [10]. Bijlard et al. recommend a BED 10 of 19.2 Gy (2 x 6 Gy) based on their retrospective analysis, which corresponds to an EQD2 10 of 16 Gy. Here the recurrence rate was also less than 10%. A common HDR fraction schedule is 3 x 6 Gy at 5 mm depth starting a least within 7 hours after surgery [6] and two fractions the following day. Other frequently used schedule is 2 x 7 Gy at 5 mm, starting the day of surgery and a second dose the day after, and single dose schedules (1 x 13 Gy at 5-7 mm) is also described [15]. Important is to prescribe the dose in relation to the depth in which the catheter is placed. For the postoperative mould application, the doses range from 12 Gy in 3-4 fractions to 20 Gy in 4 fractions.

9. DOSIMETRY

For image guided brachytherapy the reference isodose should cover the PTV as described before. For interstitial brachytherapy without imaging the reference isodose should be least at 5 mm from the scar, encompassing a target volume as described above with a total length equal to the affected skin length. Therefore, the first and last source position should be 5 mm beyond the surgical scar, and that the isodose distribution at the end of the target volume should be wide enough to cover the wounds made at the puncture site. We recommend keeping equal dwell times over the whole source trajectory and not to use geometrical optimization to create a cylindrical instead of a cigar-like shape of the prescription isodose. Hot spots at entrance and exit points should be avoided, because they will lead to hyperpigmentation of the skin at entrance and exit points of the source. For the mould application the distance of the reference isodose is at 5 mm depth.

11. MONITORING

The implant site should be carefully monitored during the stay in the department. No acute side effects besides normal wound healing are to be expected. Extreme care should be taken to keep the wound sterile and avoid additional trauma and Infection. Also, bruising and loosened stitches have been associated with recurrence risk of the keloid [3]. Removal of the skin suture is carried out one week after leaving the hospital.

10. DOSE, DOSE RATE AND FRACTIONATION

The optimal dose and fractionation regimen for the treatment of keloids is still unclear. The literature recommends a minimum dose of 20 Gy BED 10 and 30 Gy BED 10 [10, 11], This corresponds to an EQD2 of 20.4 Gy and 25 Gy for an α/β value of 10 Gy based on the assumption that keloids behave like acutely reacting tissue (see table 32.1). One of the most widely used treatment regimens is 3 x 6 Gy at 5 mm, which corresponds to a BED 10 of 28.8 Gy (24 Gy EQD2 10 ).

12. RESULTS

Almost all the data in the literature is based on retrospective monocentric analyses. Table 32.2 lists the outcome of brachytherapy for keloids by dose rate technique and method of application. Only a few institutes have reported a standardised procedure.