In-vivo dosimetric analysis in total skin electron beam therapy

Physical and clinical results of a radiation bra in patients treated with total skin electron beam therapy

Total skin electron beam therapy (TSEBT) in female patients with large or pendulous breasts is usually associated with shaded inframammary folds. In this analysis, 18 patients with cutaneous malignancy and pendulous breasts were irradiated with a radiation bra and five patients received TSEBT without bra. All patients had moderate or severe sagging of the breasts. The median inframammary dose in the radiation bra group was 89% of the prescription dose versus 4% in the group without bra. The usage of the radiation bra enables an adequate radiation dose for the inframammary folds during TSEBT with no additional local irradiation.

The evolving role of reduced-dose total skin electron beam therapy in skin malignancies: the renaissance of a rare indication

Definitive radiation therapy is an effective local treatment for several cutaneous malignancies. Patients with diffuse or generalized skin manifestations might require total skin electron beam therapy (TSEBT) as an alternative treatment to the chasing technique. In this short communication, we highlight the evolving role of TSEBT and present its role in various forms of skin malignancies.

Ultrahypofractionated Low-Dose Total Skin Electron Beam in Advanced-Stage Mycosis Fungoides and Sézary Syndrome

PURPOSE

The aim of this study was to assess the safety and efficacy of an ultrahypofractionated low-dose total skin electron beam therapy (TSEBT) regimen in patients with advanced mycosis fungoides (MF) or Sézary syndrome (SS).

METHODS AND MATERIALS

In this multicenter observational study from 5 German centers, 18 total patients with MF or SS underwent TSEBT with a total dose of 8 Gy in 2 fractions. The primary endpoint was the overall response rate.

RESULTS

Fifteen of 18 patients with stage IIB-IV MF or SS were heavily pretreated with a median of 4 prior systemic therapies. The overall response rate was 88.9% (95% confidence interval [CI], 65.3-98.6), with 3 complete responses (16.9%; 95% CI, 3.6-41.4). At a median follow-up period of 13 months, the median time to next treatment (TTNT) was 12 months (95% CI, 8.2-15.8), and the median progression-free survival was 8 months (95% CI, 2-14). A significant reduction in the modified severity-weighted assessment tool, total Skindex-29 score (Bonferroni-corrected P < .005), and all subdomains (Bonferroni-corrected P < .05) was observed after TSEBT. Half of the irradiated patients (n = 9) developed grade 2 acute and subacute toxicities. One patient had confirmed grade 3 acute toxicity. Chronic grade 1 toxicity has been observed in 33% of patients. Patients with erythroderma/SS or prior radiation therapy appear at higher risk of skin toxicities.

CONCLUSIONS

TSEBT with 8 Gy in 2 fractions achieves good disease control and symptom palliation with acceptable toxicity, greater convenience, and fewer hospital visits.

Patient Dose Analysis Using GafchromicTM EBT3 Film: A Retrospective Study with a Four Dual-Field Technique in Total Skin Electron Therapy

OBJECTIVE

The Six dual-field is the most commonly used treatment technique in total skin electron therapy (TSET). Because of the prolonged treatment period, the patient may experience discomfort, and routine radiotherapy treatments may be affected. This reflects the idea of using a modified technique in TSET. The study aims to report our experience with the four dual-field technique and review the in-vivo dosimetry using gafchromic film.

MATERIALS AND METHODS

The in-vivo dosimetry reports using gafchromic EBT-3 films of 12 patients who received TSET with the four dual-field techniques in our hospital were analysed in this study. The dosimetric parameter including percentage depth dose, dose homogeneity, flatness and symmetry were analysed in this study.

RESULTS AND DISCUSSION

For all the patients, the mean dose to the skin was close to the prescription dose, and it was within 10% (99.3%-103%) of the prescription dose. The standard deviation was observed between 5.8 and 12.4 cGy. According to international standards, all of the measured dosimetric parameters were within the acceptable limit and thereby validating our technique.  The in-vivo dosimetry study using radiochromic film in TSET is relatively uncommon. So, based on our results, gafchromic films are a viable choice. The objective of our four dual-field techniques is to reduce the overall treatment time on the machine, whereas our study shows a time reduction when compared to regular techniques, which aids in the smooth operation of daily routines.

CONCLUSION

The preliminary results of this novel modified technique in TSET demonstrated favourable effectiveness with minimal skin toxicity. This four dual-field technique is simple and easy to implement. Comparatively, this study shows the dose homogeneity of ±10% and better dose in the underdose areas proving the reliability and homogeneity of four-dual field technique.

Electron beam detection in radiotherapy using a capacitor dosimeter equipped with a silicon photodiode

In this study, a newly developed capacitor dosimeter was evaluated using electron beams commonly utilized in radiotherapy. The capacitor dosimeter comprised a silicon photodiode, 0.47-μF capacitor, and dedicated terminal (dock). Before electron beam irradiation, the dosimeter was charged using the dock. The doses were measured without using a cable by reducing the charging voltages using the currents from the photodiode during irradiation. A commercially available parallel-plane-type ionization chamber and solid-water phantom were used for dose calibration with an electron energy of 6 MeV. In addition, the depth doses were measured using a solid-water phantom at electron energies of 6, 9, and 12 MeV. The doses were proportional to the discharging voltages, and the maximum dose difference in the calibrated doses measured using a two-point calibration was approximately 5% in the range of 0.25-1.98 Gy. The depth dependencies at energies of 6, 9, and 12 MeV corresponded to those measured using the ionization chamber.

Investigation of total skin helical tomotherapy using a 3D-printed total skin bolus

OBJECTIVE

To investigate the effectiveness of using a 3D-printed total skin bolus in total skin helical tomotherapy for the treatment of mycosis fungoides.

MATERIALS AND METHODS

A 65-year-old female patient with a 3-year history of mycosis fungoides underwent treatment using an in-house desktop fused deposition modelling printer to create a total skin bolus made of a 5-mm-thick flexible material, which increased the skin dose through dose building. The patient's scan was segmented into upper and lower sections, with the division line placed 10 cm above the patella. The prescription was to deliver 24 Gy over 24 fractions, given 5 times per week. The plan parameters consisted of a field width of 5 cm, pitch of 0.287 and modulation factor of 3. The complete block was placed 4 cm away from the planned target region to reduce the area of the internal organs at risk, especially the bone marrow. Dose delivery accuracy was verified using point dose verification with a "Cheese" phantom (Gammex RMI, Middleton, WI), 3D plane dose verification with ArcCHECK (Model 1220, Sun Nuclear, Melbourne, FL), and multipoint film dose verification. Megavoltage computed tomography guidance was also utilized to ensure the accuracy of the setup and treatment.

RESULTS

A 5-mm-thick 3D-printed suit was used as a bolus to achieve a target volume coverage of 95% of the prescribed dose. The conformity index and homogeneity index of the lower segment were slightly better than those of the upper segment. As the distance from the skin increased, the dose to the bone marrow gradually decreased, and the dose to other organs at risk remained within clinical requirements. The point dose verification deviation was less than 1%, the 3D plane dose verification was greater than 90%, and the multipoint film dose verification was less than 3%, all of which confirmed the accuracy of the delivered dose. The total treatment time was approximately 1.5 h, which included 0.5 h of wearing the 3D-printed suit and 1 h with the beam on. Patients only experienced mild fatigue, nausea or vomiting, low-grade fever, and grade III bone marrow suppression.

CONCLUSION

The use of a 3D-printed suit for total skin helical tomotherapy can result in a uniform dose distribution, short treatment time, simple implementation process, good clinical outcomes, and low toxicity. This study presents an alternative treatment approach that can potentially yield improved clinical outcomes for mycosis fungoides.

Development of a real-time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder

PURPOSE

A real-time solar cell based in vivo dosimetry system (SC-IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC-IVD in electron beam therapy.

METHODS

A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC-IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6-20 MeV electron beam energy, by the signal obtained using the SC-IVD. Dosimetric characteristics of SC-IVDs containing variable quantities of scintillating powder (0-500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC-IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC-IVD was on the surface. Finally, the accuracy of surface doses measured using the SC-IVD was evaluated by comparison with surface doses measured using a Markus chamber.

RESULTS

Charge measured using the SC-IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC-IVD increased as the beam angle increased. The presence of the SC-IVD on the surface of a phantom resulted in a 0.5%-2.2% reduction in dose at R90 for 6-20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC-IVD system and Markus chamber differed by less than 5%.

CONCLUSIONS

The dosimetric characteristics of the SC-IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC-IVD allows it to be attached to a patient's skin, enabling real-time and cost-effective measurement.

Low-dose total skin electron beam therapy plus oral bexarotene maintenance therapy for cutaneous T-cell lymphoma

BACKGROUND

Total skin electron beam therapy (TSEBT) combined with systemic therapy or maintenance treatment is a reasonable approach to enhance the remission rate and duration in mycosis fungoides (MF) and Sézary syndrome (SS). This study assesses the efficacy of oral bexarotene therapy after low-dose TSEBT for patients with MF and SS.

METHODS

In this prospective observational study, we recruited MF/SS patients for treatment with low-dose total skin electron beam therapy (TSEBT) with or without bexarotene therapy to describe outcomes and toxicities.

RESULTS

Forty-six subjects with MF or SS underwent TSEBT between 2016 and 2021 at our institute. Following TSEBT, 27 patients (59 %) received oral bexarotene treatment. The median follow-up was 13 months. The overall response rate (ORR) for the cohort was 85 %. The response rate was significantly higher with combined modality (CM) than TSEBT alone (96 % vs. 68 %, p = 0.03). Median progression-free survival (PFS) for the CM was 17 months versus five months following TSEBT alone (p = 0.001). One patient (4 %) in the retinoid group discontinued the bexarotene therapy because of adverse events. The administration of bexarotene therapy did not increase radiation-related toxicities.

CONCLUSIONS

Response rate and progression-free survival might be improved with TSEBT in combination with oral bexarotene compared to TSEBT alone.

Sweeping-beam technique with electrons for large treatment areas as total skin irradiation : Dosimetric and technical aspects of a modified Stanford technique

PURPOSE

Total skin electron beam therapy (TSEBT) is still a technical and therapeutic challenge today. Thus, we developed TSEBT using a sweeping-beam technique.

METHODS

For treatment delivery, a linear accelerator Versa HD (ELEKTA, Stockholm, Sweden) with high-dose-rate electrons (HDRE) was used with a dose rate of 9000 MU/min. Dosimetry quality assurance was performed by multiple measurements with film dosimetry, 2D array, and Roos chamber.

RESULTS

Clinical experience shows that treatment durations of 75 to 90 min are usual for the Stanford technique without using HDRE. With this new sweeping-beam irradiation technique, the total treatment time of a daily fraction could be reduced to 20 min while keeping over- and underdosing low. The treatment area is about 60 cm × 200 cm and the dose distribution is uniform within 2% and 5% in vertical and horizontal directions, respectively. Initially, the electron energy of 6 MeV is reduced to 3.2 MeV by 1‑cm polymethylmethacrylat (PMMA) scatter and the irradiation conditions of a source-surface distance (SSD) of 350 cm. The photon contamination drops to under 1%.

CONCLUSION

These results show that the mean dose to total skin varies between 1.3 and 1.8 Gy. The sweeping-beam technique with electrons has a homogeneous dose distribution in connection with a short treatment time.

Monte Carlo study on dose distributions from total skin electron irradiation therapy (TSET)

Total skin electron therapy (TSET) has been used to treat mycosis fungoides since the 1950s. Practitioners of TSET rely on relatively crude, phantom-based point measurements for commissioning and treatment plan dosimetry. Using Monte Carlo simulation techniques, this study presents whole-body dosimetry for a patient receiving rotational, dual-field TSET. The Monte Carlo codes, BEAMnrc/DOSXYZnrc, were used to simulate 6 MeV electron beams to calculate skin dose from TSET. Simulations were validated with experimental measurements. The rotational dual-field technique uses extended source-to-surface distance with an acrylic beam degrader between the patient and incident beams. Simulations incorporated patient positioning: standing on a platform that rotates during radiation delivery. Resultant patient doses were analyzed as a function of skin depth-dose coverage and evaluated using dose-volume-histograms (DVH). Good agreement was obtained between simulations and measurements. For a cylinder with a 30 cm diameter, the depths that dose fell to 50% of the surface dose was 0.66 cm, 1.15 cm and 1.42 cm for thicknesses of 9 mm, 3 mm and without an acrylic scatter plate, respectively. The results are insensitive to cylinder diameter. Relatively uniform skin surface dose was obtained for skin in the torso area although large dose variations (>25%) were found in other areas resulting from partial beam shielding of the extremities. To achieve 95% mean dose to the first 5 mm of skin depth, the mean dose to skin depth of 5-10 mm and depth of 10-15 mm from the skin surface was 74% (57%) and 50% (25%) of the prescribed dose when using a 3mm (9 mm) thickness scatter plate, respectively. As a result of this investigation on patient skin dose distributions we changed our patient treatments to use a 3 mm instead of a 9 mm thickness Acrylic scatter plate for clinically preferred skin depth dose coverage.

In-vivo dosimetry in Total Skin Electron Therapy: Literature review

Aim:

Total Skin Electron Therapy (TSET) is a specialised radiotherapy technique to treat cutaneous T-cell lymphomas. The purpose of this article is to review different in-vivo dosimetry techniques and to identify further research direction in TSET

Materials and methods:

Studies focused on in-vivo dosimetry in TSET were included. Studies based on absolute dosimetry in TSET were excluded and no restriction was applied regarding the type of treatment technique and the type of dosimeter.

Result:

From the review of articles, we have found that obesity index and patient position during treatment plays a major role in underdose or overdose in TSET. Many studies favour individualised boost dose to patients. The analysis showed that thermoluminescent dosimeters are the most widely used dosimeters in TSET, and time-consuming is the only drawback in the use of dosimetry.

Conclusion:

Study showed that the practice of using in-vivo dosimetry would be better way to treat TSET by ensuring accuracy of dose delivery to the patients. Further, only limited studies are available for dosimetry with radiochromic films. With this observation, we have started exploring the use of radiochromic film in our TSET dosimetry, and the results can be analysed to standardise the technique in future.

Low-dose total skin electron beam therapy: Quality of life improvement and clinical impact of maintenance and adjuvant treatment in patients with mycosis fungoides or Sezary syndrome

PURPOSE

Total skin electron beam therapy (TSEBT) has proved to be a safe and effective treatment for cutaneous T‑cell lymphomas. Here, we examined the impact of this treatment on patient quality of life and outcome.

PATIENTS AND METHODS

Forty-four patients with mycosis fungoides (MF) or Sezary syndrome (SS) received 48 TSEBT courses with a median dose of 12 Gy within the past 8 years at our institute. Patient and treatment characteristics for these cases as well as the impact of TSEBT on quality of life and duration of response were retrospectively analyzed and compared.

RESULTS

The median modified Severity-Weighted Assessment Tool score before the start of TSEBT was 44. The overall response rate was 88%, with a complete response (CR) rate of 33%. The median follow-up period was 13 months. The median duration of response (DOR) and progression-free survival (PFS) for the entire cohort were 10 months and 9 months, respectively. Patient-reported symptom burden was measured with the Dermatological Life Quality Index and Skindex-29 questionnaires. The mean symptom reductions were 6 ± 8 (P = 0.005) and 21 ± 24 (P = 0.002), respectively. In the Functional Assessment of Cancer Therapy-General Assessment, significant improvements in the emotional (P = 0.03) domains were observed after TSEBT. Patients who received maintenance or adjuvant treatments had a longer PFS (P = 0.01).

CONCLUSION

TSEBT improved disease symptoms and significantly improved emotional domains of patients' quality of life in patients with MF or SS. In addition, our results indicate that maintenance or adjuvant therapy after TSEBT may improve the PFS.

Total skin electron beam therapy rationalization and utility of in vivo dosimetry in a high-volume centre

OBJECTIVE

This paper reports on the rationalization of a substantial pool of in vivo dosimetry (IVD) data from patients treated with total skin electron beam therapy (TSEBT) and the application of this to verify the accurate delivery of TSEBT when changing linac manufacturer.

METHODS

Thermoluminescent dosimeter IVD data from 149 patients were analyzed comparing the population mean and standard deviation for each site. The number of sites required to confirm the prescribed dose were reviewed considering both dosimetric and clinical relevance. The reduced sites were then used to assess the continued dosimetric accuracy on new equipment and the results were compared statistically using the Mann-Witney test.

RESULTS

The trunk dose measurement points were reduced from nine to six and five extra trunk sites were identified and reviewed clinically prior to removal.Following change in manufacturer the trunk dose points showed no statistically significant change and confirmed that patients had received within 1.3% of the intended mean trunk dose using both delivery methods.A statistically significant change in 4 out of the 13 extra trunk sites was seen following the move to the new centre. However, all but one site showed a change of less than 1 standard deviation.

CONCLUSION

The total number of measurement points per patient were reduced from 27 to 19 which constituted a 25% saving in preparation and read out.Accurate delivery of prescribed dose was confirmed following measurement point reduction for treatments delivered on linacs from two different manufacturers.

ADVANCES IN KNOWLEDGE

Proven methodology for rationalization of IVD measurements for TSEBT.

Clinical application of Total Skin Electron Beam (TSEB) therapy for the management of T cell cutaneous lymphomas. The evolving role of low dose (12 Gy) treatment schedule

BACKGROUND & PURPOSE

Although rare, cutaneous lymphomas represent a separate entity in hematologic oncology. T cell origin lymphomas are most common, with Mycosis Fungoides (MF) accounting for about 50-70% of cases. Sezary Syndrome (SS), which represents the leukemic varian of MF, accounts for 3% of Cutaneous T Cell Lymphomas (CTCL). Total Skin Electron Beam Therapy (TSEB) is included at the mainstream of treatment choices for CTCL. The scope of this study is to evaluate the effectiveness and toxicity of two treatment schedules of TSEB.

METHODS AND MATERIALS

We report our experience with TSEB in the management of MF and SS, as of 14 patients treated in our institution from 2011 to 2015. 8 patients received the 12 Gy (low dose) scheme while 6 patients were managed with 36 Gy (standard or full dose scheme) according to six dual field Stanford technique. The endpoints were overall response rate, duration of response and toxicity of treatment.

RESULTS

After a median follow up of 2.5 years we noted excellent treatment outcome, with both schemes being well tolerated and resulting in comparable response rates. The overall response rate for both treatment regimens was over 87.5%. Treatment was well tolerated with mild toxicity.

CONCLUSION

The role of TSEB in the management of MF and SS is well established. The low dose TSEB schedule of 12 Gy is an effective treatment option, since therapeutic results are more than acceptable, compliance is excellent and toxicity is minimal. Moreover, the evidence that it can be repeated safely makes it more attractive than the standard 36 Gy scheme, when a patient is referred to radiation treatment according to treatment guidelines.