X-ray surface irradiation

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Definition
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Treatment of the skin surface with X-rays. In some dermatological centers the therapy with so-called soft X-ray devices is still common for certain indications. In this radiation therapy, the penetration depth of the X-rays into the tissue is relatively low, so that the deeper tissue is spared. The still operated soft beam devices (mostly Dermopan/Fa. Siemens) allow operating voltages of the X-ray tube between 10 and 50 kV (at 25 mA). The range up to and including 10 kV is called boundary radiation therapy (Bucky rays). The dose of X-rays is measured in Gray (Gy) (previously: rad = radiation absorbed dose).

Effects
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  • At the end of irradiation, acute radiodermatitis occurs in the surrounding healthy skin (and in the skin above the tumour), an erosive dermatitis (erosive reaction), which for many therapists indicates the individually sufficient irradiation dose. The total dose (GD) is fractionated into daily single doses (ED) of varying strength. This fractionation results in better tissue tolerance.
  • Late consequences of X-ray radiation are chronic radiodermatitis with hyper- and depigmentation, fibrotic remodelling of the corium, radiation ulcers as well as malignant epithelial and connective tissue tumours in loco.

Indication
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The indication for X-ray therapy is increasingly rarely given in dermatology, mostly due to sufficient or better alternative methods without the known late damage of X-ray therapy or in the absence of functioning X-ray equipment (the devices are no longer manufactured).
  • Basal cell carcinoma: Most frequent indication, especially in elderly people. For a solid basal cell carcinoma a total dosage (GD) of 50-70 Gy (43-50 kV/25 mA) is necessary. Single doses (ED) of 4-5 Gy 5 times/week.
  • M. Bowen: Common indication. The total dosage (GD) is 25-30 Gy (29 kV/25 mA). The total dose is fractionated into single doses (ED) of 5 Gy at intervals of 2 days.
  • Lentigo maligna: Frequent indication; especially in elderly people who can hardly be expected to undergo major surgery (note the special localization of lentigo maligna!). According to Miescher, a total dosage (GD) of 100 Gy (10 kV/25 mA = soft jet technique) is necessary for a lentigo maligna. The total dose is fractionated in ED of 20 Gy in intervals of 3-4 days
  • Diffuse melanoma metastases of the skin: palliative measure if other therapeutic measures are exhausted; in this indication other radiation sources (electron accelerators) are to be preferred. GD 90-10 Gy; ED 5 Gy.
  • Skin lymphomas: Common indication for isolated cutaneous B- and T-cell lymphomas of the skin. A total dosage (GD) of 25-30 Gy (50 kV/25 mA) is required for nodular lymphoma. The GD is fractionated in ED of 2-5 Gy at intervals of 2 days. The results are initially very convincing. With repeated x-ray irradiation an increasing radiation resistance is observed. In the case of erythrodermic T-cell lymphomas, remote x-ray irradiation of the whole body should be considered if there is any other resistance to treatment. The focal skin distance (FHA) is 2 m; the GD is 10-15 Gy (50 kV/25 mA, without aluminium filter), the ED is 0.5-1.5 Gy daily. Irradiation alternately from the front and the back.

Contraindication
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X-ray applications for infant hemangiomas, naevi flammei and chronic inflammatory dermatoses.

Literature
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  1. Hoppe RT (2003) Mycosis fungoides: radiation therapy. Dermatol Ther 16: 347-354
  2. McWilliams RR et al (2003) Treatment of brain metastases from melanoma. Mayo Clin Proc 78: 1529-1536
  3. Miescher G (1953) The latest development in dermatological radiotherapy. Dermatologica 107: 225-230
  4. Zagrodnik B et al (2003) Superficial radiotherapy for patients with basal cell carcinoma: recurrence rates, histologic subtypes, and expression of p53 and Bcl-2. cancer 98: 2708-2714

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Last updated on: 29.10.2020