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A pilot study of ultrasound-guided electronic brachytherapy for skin cancer.

Goyal U, Kim Y, Tiwari HA, Witte R, Stea B - J Contemp Brachytherapy (2015)

Bottom Line: All patients had a complete response and no failures have occurred with a median follow-up of 12 months (range of 6-22 months).Also, no prolonged skin toxicities have occurred.A routinely available radiological US unit can objectively determine depth and lateral extension of NMSC lesions for more accurate eBT treatment planning, and should be considered in future eBT treatment guidelines.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology.

ABSTRACT

Purpose: Electronic brachytherapy (eBT) has gained acceptance over the past 5 years for the treatment of non-melanomatous skin cancer (NMSC). Although the prescription depth and radial margins can be chosen using clinical judgment based on visual and biopsy-derived information, we sought a more objective modality of measurement for eBT planning by using ultrasound (US) to measure superficial (< 5 mm depth) lesions.

Material and methods: From December 2013 to April 2015, 19 patients with 23 pathologically proven NMSCs underwent a clinical examination and US evaluation of the lesions prior to initiating a course of eBT. Twenty lesions were basal cell carcinoma and 3 lesions were squamous cell carcinoma. The most common location was the nose (10 lesions). A 14 or 18 MHz US unit was used by an experienced radiologist to determine depth and lateral extension of lesions. The US-measured depth was then used to define prescription depth for eBT planning without an added margin. A margin of 7 mm was added radially to the US lateral extent measurements, and an appropriate cone applicator size was chosen to cover the target volume.

Results: The mean depth of the lesions was 2.1 mm with a range of 1-3.4 mm, and the mean largest diameter of the lesions was 8 mm with a range of 2.6-20 mm. Dose ranged from 32-50 Gy in 8-20 fractions with a median dose of 40 Gy in 10 fractions. All patients had a complete response and no failures have occurred with a median follow-up of 12 months (range of 6-22 months). Also, no prolonged skin toxicities have occurred.

Conclusions: A routinely available radiological US unit can objectively determine depth and lateral extension of NMSC lesions for more accurate eBT treatment planning, and should be considered in future eBT treatment guidelines.

No MeSH data available.


Related in: MedlinePlus

Default prescription depth toxicity. Two lesions on the lower extremity were treated to 40 Gy in 8 fractions (5 Gy per fraction) twice per week using a 35 mm cone based on clinical exam and default depth of 3 mm in our early electronic brachytherapy (eBT) experiences. The patient developed a non-healing grade 4 ulceration that persisted even after 4 months post-eBT. Although this toxicity could be due to a number of contributing factors, it illustrates the need for a more precise and accurate depth of prescription. A) Pre-treatment, B) 4 months post-eBT
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Figure 0001: Default prescription depth toxicity. Two lesions on the lower extremity were treated to 40 Gy in 8 fractions (5 Gy per fraction) twice per week using a 35 mm cone based on clinical exam and default depth of 3 mm in our early electronic brachytherapy (eBT) experiences. The patient developed a non-healing grade 4 ulceration that persisted even after 4 months post-eBT. Although this toxicity could be due to a number of contributing factors, it illustrates the need for a more precise and accurate depth of prescription. A) Pre-treatment, B) 4 months post-eBT

Mentions: Because of eBT low energy X-rays, the maximum dose is at the surface, and the dose at 5 mm depth is 50-60% of the surface dose depending upon the applicator, e.g., if the prescription depth is 5 mm then ~200% of dose is at the skin surface [24, 25]. In a previously published study using Xoft eBT for lesions 1-7 mm thick treated with 40 Gy in 8 fractions, treatment resulted in a local control of 100% and an excellent cosmesis in 93% of patients with no toxicity at a follow-up of 1 year [18]. In this particular study, CT scans were used to estimate the depth of treatment. In many clinics, however, a default depth is selected for eBT calculations and is used universally for all patients. The lateral extension is usually determined with visual inspection on the skin surface and a varying margin is applied based on the physician's discretion [6, 7]. In our initial eBT experience, using clinical estimates of depth and lateral extent, led to complications such as grade 4 skin necrosis and prolonged wound healing, especially with thicker lesions and lower extremity lesions (Figure 1). This motivated us to investigate a more accurate approach in choosing an applicator size and dose depth prescription by utilizing clinically available ultrasound (US) to measure the depth and lateral extent in order to prevent overdosing the skin. Such US methods have been previously investigated with HDR-BT [13].


A pilot study of ultrasound-guided electronic brachytherapy for skin cancer.

Goyal U, Kim Y, Tiwari HA, Witte R, Stea B - J Contemp Brachytherapy (2015)

Default prescription depth toxicity. Two lesions on the lower extremity were treated to 40 Gy in 8 fractions (5 Gy per fraction) twice per week using a 35 mm cone based on clinical exam and default depth of 3 mm in our early electronic brachytherapy (eBT) experiences. The patient developed a non-healing grade 4 ulceration that persisted even after 4 months post-eBT. Although this toxicity could be due to a number of contributing factors, it illustrates the need for a more precise and accurate depth of prescription. A) Pre-treatment, B) 4 months post-eBT
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663218&req=5

Figure 0001: Default prescription depth toxicity. Two lesions on the lower extremity were treated to 40 Gy in 8 fractions (5 Gy per fraction) twice per week using a 35 mm cone based on clinical exam and default depth of 3 mm in our early electronic brachytherapy (eBT) experiences. The patient developed a non-healing grade 4 ulceration that persisted even after 4 months post-eBT. Although this toxicity could be due to a number of contributing factors, it illustrates the need for a more precise and accurate depth of prescription. A) Pre-treatment, B) 4 months post-eBT
Mentions: Because of eBT low energy X-rays, the maximum dose is at the surface, and the dose at 5 mm depth is 50-60% of the surface dose depending upon the applicator, e.g., if the prescription depth is 5 mm then ~200% of dose is at the skin surface [24, 25]. In a previously published study using Xoft eBT for lesions 1-7 mm thick treated with 40 Gy in 8 fractions, treatment resulted in a local control of 100% and an excellent cosmesis in 93% of patients with no toxicity at a follow-up of 1 year [18]. In this particular study, CT scans were used to estimate the depth of treatment. In many clinics, however, a default depth is selected for eBT calculations and is used universally for all patients. The lateral extension is usually determined with visual inspection on the skin surface and a varying margin is applied based on the physician's discretion [6, 7]. In our initial eBT experience, using clinical estimates of depth and lateral extent, led to complications such as grade 4 skin necrosis and prolonged wound healing, especially with thicker lesions and lower extremity lesions (Figure 1). This motivated us to investigate a more accurate approach in choosing an applicator size and dose depth prescription by utilizing clinically available ultrasound (US) to measure the depth and lateral extent in order to prevent overdosing the skin. Such US methods have been previously investigated with HDR-BT [13].

Bottom Line: All patients had a complete response and no failures have occurred with a median follow-up of 12 months (range of 6-22 months).Also, no prolonged skin toxicities have occurred.A routinely available radiological US unit can objectively determine depth and lateral extension of NMSC lesions for more accurate eBT treatment planning, and should be considered in future eBT treatment guidelines.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology.

ABSTRACT

Purpose: Electronic brachytherapy (eBT) has gained acceptance over the past 5 years for the treatment of non-melanomatous skin cancer (NMSC). Although the prescription depth and radial margins can be chosen using clinical judgment based on visual and biopsy-derived information, we sought a more objective modality of measurement for eBT planning by using ultrasound (US) to measure superficial (< 5 mm depth) lesions.

Material and methods: From December 2013 to April 2015, 19 patients with 23 pathologically proven NMSCs underwent a clinical examination and US evaluation of the lesions prior to initiating a course of eBT. Twenty lesions were basal cell carcinoma and 3 lesions were squamous cell carcinoma. The most common location was the nose (10 lesions). A 14 or 18 MHz US unit was used by an experienced radiologist to determine depth and lateral extension of lesions. The US-measured depth was then used to define prescription depth for eBT planning without an added margin. A margin of 7 mm was added radially to the US lateral extent measurements, and an appropriate cone applicator size was chosen to cover the target volume.

Results: The mean depth of the lesions was 2.1 mm with a range of 1-3.4 mm, and the mean largest diameter of the lesions was 8 mm with a range of 2.6-20 mm. Dose ranged from 32-50 Gy in 8-20 fractions with a median dose of 40 Gy in 10 fractions. All patients had a complete response and no failures have occurred with a median follow-up of 12 months (range of 6-22 months). Also, no prolonged skin toxicities have occurred.

Conclusions: A routinely available radiological US unit can objectively determine depth and lateral extension of NMSC lesions for more accurate eBT treatment planning, and should be considered in future eBT treatment guidelines.

No MeSH data available.


Related in: MedlinePlus