Superficial radiotherapy (SRT-100) for refractory plantar warts: An alternative noninvasive treatment strategy

BACKGROUND

Verrucas that occur on the soles of the feet are called plantar warts, most of which can recur repeatedly and are difficult to eradicate. Hypertrophic and refractory plantar warts are often accompanied by pain and discomfort, which cause many inconveniences in patients' daily lives.

AIM

This study aimed to analyze the therapeutic effect of superficial radiotherapy (SRT-100) on refractory plantar warts and further create favorable conditions for the subsequent treatment of this disease with a high recurrence rate.

METHODS

A retrospective analysis was conducted for refractory plantar warts treated with superficial radiotherapy in our outpatient department from January to June 2023.

RESULTS

A total of 30 patients were included in our study (median age, 33 years). The female-to-male ratio was 1:3.29. Two to six months after radiotherapy, all of the warts subsided in 23 (76.67%) patients, most of the warts subsided in 4 (13.33%) patients, 3 (10%) patients did not respond to treatment, and 7 (23.33%) patients had recurrent or new warts after their warts subsided.

CONCLUSIONS

Most patients with refractory plantar warts improved after superficial radiotherapy. Our study presented that men are more susceptible to plantar warts than women, and young and middle-aged people are the main population affected by the disease. Superficial radiotherapy is an effective treatment for refractory plantar warts, which can quickly remove the warts in a short period. It is safe and noninvasive, with minimal adverse reactions. Some patients relapse after the lesion is clear, and superficial radiotherapy can create favorable conditions for the subsequent treatment of viral warts in clinical practice.

Machine characterization and central axis depth dose data of a superficial x-ray radiotherapy unit

Objectives. The purpose of this study is to present data from the clinical commissioning of an Xstrahl 150 x-ray unit used for superficial radiotherapy,Methods. Commissioning tasks included vendor acceptance tests, timer reproducibility, linearity and end-effect measurements, half-value layer (HVL) measurements, inverse square law verification, head-leakage measurements, and beam output calibration. In addition, percent depth dose (PDD) curves were determined for different combinations of filter/kV settings and applicators. Automated PDD water phantom scans were performed utilizing four contemporary detectors: a microDiamond detector, a microSilicon detector, an EDGE detector, and a PinPoint ionization chamber. The measured PDD data were compared to the published values in BJR Supplement 25,Results. The x-ray unit's mechanical, safety, and radiation characteristics were within vendor-stated specifications. Across sixty commissioned x-ray beams, the PDDs determined in water using solid state detectors were in excellent agreement with the BJR 25 data. For the lower (<100 kVp) and medium-energy (≥100 kVp) superficial beams the average agreement was within [-3.6,+0.4]% and [-3.7,+1.4]% range, respectively. For the high-energy superficial (low-energy orthovoltage) x-rays at 150 kVp, the average difference for the largest 20 × 20 cm²collimator was (-0.7 ± 1.0)%,Conclusions. This study presents machine characterization data collected for clinical use of a superficial x-ray unit. Special focus was placed on utilizing contemporary detectors and techniques for the relative PDD measurements using a motorized water phantom. The results in this study confirm that the aggregate values published in the BJR 25 report still serve as a valid benchmark when comparing data from site-specific measurements, or the reference data for clinical utilization without such measurements,Advances in knowledge. This paper presents comprehensive data from the acceptance and commissioning of a modern kilovoltage superficial x-ray radiotherapy machine. Comparisons between the PDD data measured in this study using different detectors and BJR 25 data are highlighted.

Off-axis dose distribution with stand-in and stand-off configurations for superficial radiotherapy treatments

Current practice when delivering dose for superficial skin radiotherapy is to adjust the monitor units so that the prescribed dose is delivered to the central axis of the superficial unit applicator. Variations of source‐to‐surface distance due to patient’s anatomy protruding into the applicator or extending away from the applicator require adjustments to the monitor units using the inverse square law. Off‐axis dose distribution varies significantly from the central axis dose and is not currently being quantified. The dose falloff at the periphery of the field is not symmetrical in the anode–cathode axis due to the heel effect. This study was conducted to quantify the variation of dose across the surface being treated and model a simple geometric shape to estimate a patient’s surface with stand‐in and stand‐off. Isodose plots and color‐coded dose distribution maps were produced from scans of GAFChromic EBT‐3 film irradiated by a Gulmay D3300 orthovoltage x‐ray therapy system. It was clear that larger applicators show a greater dose falloff toward the periphery than smaller applicators. Larger applicators were found to have a lower percentage of points above 90% of central axis dose (SA90). Current clinical practice does not take this field variation into account. Stand‐in can result in significant dose falloff off‐axis depending on the depth and width of the protrusion, while stand‐off can result in a flatter field due to the high‐dose region near the central axis being further from the source than the peripheral regions. The central axis also received a 7% increased or decreased dose for stand‐in or stand‐off, respectively.

Novel treatment options for nonmelanoma skin cancer: focus on electronic brachytherapy

Nonmelanoma skin cancer (NMSC) is an increasing health care issue in the United States, significantly affecting quality of life and impacting health care costs. Radiotherapy has a long history in the treatment of NMSC. Shortly after the discovery of X-rays and ²²⁶Radium, physicians cured patients with NMSC using these new treatments. Both X-ray therapy and brachytherapy have evolved over the years, ultimately delivering higher cure rates and lower toxicity. Electronic brachytherapy for NMSC is based on the technical and clinical data obtained from radionuclide skin surface brachytherapy and the small skin surface applicators developed over the past 25 years. The purpose of this review is to introduce electronic brachytherapy in the context of the history, data, and utilization of traditional radiotherapy and brachytherapy.

Radiotherapy treatment for nonmelanoma skin cancer

Non-melanoma skin cancer is the most common malignancy in the USA, with an estimated 3.5 million cases per year. Treatment options include surgical excision, radiation therapy (RT), photodynamic therapy and topical agents. Although surgical excision remains the mainstay of therapy, RT offers an effective alternative. RT can be used as an adjunct to surgery in high-risk situations, or in cases where surgical excision would lead to impaired cosmesis and/or functional outcomes. Radiation treatment modalities for non-melanoma skin cancers are diverse. Studies in the literature have examined the clinical effects of a wide variety of modalities, areas of the body and dosages. The most common modalities include superficial or orthovoltage RT, electron beam therapy and high dose-rate brachytherapy. This article aims to review the diverse radiotherapy treatment modalities for non-melanoma skin cancers, focusing on tumor control and toxicity.

Dosimetric characteristics of a new unit for electronic skin brachytherapy. J Contemp Brachytherapy. 2014;6:45-53. [PMID: 24790622 PMCID: PMC4003426 DOI: 10.5114/jcb.2014.40770]

Purpose

Brachytherapy with radioactive high dose rate (HDR) ¹⁹²Ir source is applied to small skin cancer lesions, using surface applicators, i.e. Leipzig or Valencia type. New developments in the field of radiotherapy for skin cancer include electronic brachytherapy. This technique involves the placement of an HDR X-ray source close to the skin, therefore combining the benefits of brachytherapy with the reduced shielding requirements and targeted energy of low energy X-rays. Recently, the Esteya^® Electronic Brachytherapy System (Esteya EBS, Elekta AB-Nucletron, Stockholm, Sweden) has been developed specifically for HDR brachytherapy treatment of surface lesions. The system provides radionuclide free HDR brachytherapy by means of a small 69.5 kV X-ray source. The purpose of this study is to obtain the dosimetric characterization required for clinical implementation, providing the detailed methodology to perform the commissioning.

Material and methods

Flatness, symmetry and penumbra, percentage of depth dose (PDD), kV stability, HVL, output, spectrum, linearity, and leakage have been evaluated for a set of applicators (from 10 mm to 30 mm in diameter).

Results

Flatness and symmetry resulted better than 5% with around 1 mm of penumbra. The depth dose gradient is about 7%/mm. A kV value of 68.4 ± 1.0 kV (k = 1) was obtained, in good agreement with manufacturer data (69.5 kV). HVL was 1.85 mm Al. Dose rate for a typical 6 Gy to 7 Gy prescription resulted about 3.3 Gy/min and the leakage value was < 100 µGy/min.

Conclusions

The new Esteya^® Electronic Brachytherapy System presents excellent flatness and penumbra as with the Valencia applicator case, combined with an improved PDD, allowing treatment of lesions of up to a depth of 5 mm in combination with reduced treatment duration. The Esteya unit allows HDR brachytherapy superficial treatment within a minimally shielded environment due its low energy.