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RADIATION THERAPY
RADIATION THERAPY
Radiation therapy is becoming increasingly popular as adjuvant therapy post-excision in the management of keloids. Radiation therapy can be performed either as external radiation or brachytherapy. External radiation therapy may require a high dose of radiation,57 while brachytherapy may lead to a more localized and targeted treatment. Brachytherapy can be further subdivided into low-dose rate (LDR), where a low-dose radioactive source is used and withdrawn after 20 to 72 hours, and a high-dose rate (HDR), where a high-dose radioactive source is applied for only 5 to 10 minutes.57 HDR may be associated with improved patient convenience.
The exact mechanism of how radiation therapy prevents scar recurrence is unknown; it is thought to function either by inhibiting fibroblast proliferation or by preventing the release of humoral or cellular factors that stimulate local fibroblasts to proliferate abnormally.57,58 Radiation therapy may also function by inhibiting angiogenesis, which is involved in keloid pathogenesis.59
Radiation therapy has been studied extensively for the treatment of keloids. Shen et al., treated 834 keloids post-excision with electron-beam radiation therapy and found a
relapse rate of 9.59%.60 De Cicco et al., treated 70 patients status-post keloid excision with brachytherapy, either LDR or HDR, and they noted a recurrence of 30.4% in the LDR group and 38% in the HDR group.61 When all treatment modalities were compared in a systematic review including 33 studies, HDR brachytherapy showed the lowest recurrence rates (10.5%) compared with LDR (21.3%) and external-beam radiation (22.2%).57 For external radiation, a shorter time interval (<7 hours) between excision and radiation treatment was associated with a lower recurrence rate (17%) as compared to a longer time interval (>24 hours), with a recurrence rate 21%, though the timing of therapy with HDR did not show this difference. While reports of adjuvant radiation after shave excision of keloids have been reported, 58 complete wound closure is generally recommended prior to radiation.
Dosing of radiation therapy varies in different protocols. Kim et al., performed a retrospective study of 39 lesions treated with keloidectomy followed by adjuvant radiation therapy. 62 The lowest rate of recurrence was noted in patients who had undergone 1,500 cGy of radiation in three fractions. This protocol is often employed, and typically is begun on the day of surgical excision.
Adjuvant radiation therapy has some limitations. Relative contraindications for radiation therapy include pregnancy, age less than 12 years old, or presence of a keloid over radiosensitive locations (such as the thyroid gland).57 Adverse events include skin erythema (early) and dyspigmentation (late).60,63 There is also a theoretical risk of malignancy, as exposure to radiation is associated with radiation-induced cancers, though to date there have been no reports of radiation-induced malignancy when used for this indication, and the overall risk of cancer is felt to be very small.64