Soft Xray Orthovolt Radiotherapy

Introduction

X-rays are electromagnetic radiations of high energy. When x-rays are used to treat superficial lesions, the energy spectrum of the x-ray beam is adjusted by selecting an appropriate combination of x-ray tube filtration and voltage, which is 30-100 kV (soft x-rays) in dermatology settings. Treatment of localized lesions and teleroentgen therapy with soft x-rays are two different approaches.

The first Nobel Prize in physics was awarded to Hans Conrad Rontgen in Wurzburg, Germany, for his discovery of x-rays in 1896. Early reports on the use of orthovolt radiotherapy in cutaneous lymphoma were published by Scholtz in 1902 (30).

Mode of Action

Ionizing radiation induces free active radicals in the tissue and hits DNA by doublestrand breaks. It has an impact on many functions such as enzyme activity, cell membrane permeability, and protein synthesis, finally resulting in the loss of reproductive integrity of the cells.

Indications

Early plaques and tumors in cutaneous lymphomas are highly radiosensitive and respond to low doses of ionizing radiation (31), provided that the half-value depth corresponds to the depth of infiltration, which in nontumoral stages of CTCL is usually a few millimeters in and beneath the epidermis.

Practical Application

For localized lesions, radiation therapy is given with D1/2 matching the depth of the lesion, in small doses of 2 Gy at weekly intervals or three times weekly until the lesion starts to involute. A total dose of 20-50 Gy is sufficient for most lesions (31).

Considering the malignant nature of the disease, additional radiation, perhaps even a second course, may be required despite side effects.

For widespread erythrodermic involvement, teleroentgen therapy with soft x-rays may be indicated. A distance of 2 m permits radiation of the entire body surface. When soft x-rays are used according to the technique described by Schirren in 1955, 50% of the surface dose is absorbed at a depth of only 2 mm (32,33). A high-output beryllium-window unit (50 kV) is used. Doses of 50-100 cGy are given daily or three times a week to the anterior, posterior, and lateral surfaces up to a total of 500-1000 cGy per course with the eyes and gonads shielded (31). There are some variations of the method in terms of distance (2 m in the technique described by Schirren in Munich (32) and 1.20 m in the Hamburg technique (34) and in terms of fractionation, which do not affect the basic principle of superficial total body "spray" irradiation.

Results

Irrespective of the technical differences, good long-term results have been reported from different centers (33,34) (Fig. 1).

Combination with Other Modalities

Topical agents especially topical cytostatic drugs (HN2, BCNU) should be avoided during irradiation. Emollient creams or ointments may be useful to treat dryness and pruritus.

Comments

Soft x-ray therapy still is an excellent treatment modality for cutaneous T-cell and B-cell lymphomas. Erythrodermic patients may profit from teleroentgen therapy.

Figure 1 Follicle center lymphoma before (left) and after (right) soft X-ray therapy.
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Responses

  • Cody Forbes
    Why soft xrays used in therapy?
    2 years ago

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