Prognosis with newly diagnosed mycosis fungoides after total skin electron radiation of 30 or 35 GY

Breaking Down the Barriers for Patients With Cutaneous T-Cell Lymphoma: Current Controversies and Challenges for Radiation Oncologists in 2024

Cutaneous T-cell lymphomas (CTCL) are a rare collection of diseases, frequently associated with diagnostic challenges and complex management dilemmas. The multidisciplinary team is vital for accurate clinico-pathological diagnoses and for collaborative therapeutic decisions throughout the management journey, which frequently involves multiple lines of therapy. Radiotherapy (RT) is a highly effective skin-directed therapy for CTCL, commonly delivered as localised fields or as total skin electron beam therapy (TSEBT). Mycosis fungoides (MF) is the most common of the CTCL, and patients typically experience high rates of morbidity and long natural histories of relapse and progression. Patients with MF typically present with incurable disease; in these patients, RT has an established role in symptom- and disease-control, achieving excellent response rates and proven therapeutic benefits. The role of RT continues to evolve, with modern practices favouring lower doses to reduce toxicity risks and allow for re-irradiation. Less commonly, there are situations where RT has an integral role in the potential cure of patients with MF: firstly, in the setting of unilesional MF where localised RT alone may be curative, and secondly, in the setting of preconditioning prior to curative-intent allogeneic hematopoietic stem cell transplant for patients with advanced MF/Sezary syndrome, where conventional-dose TSEBT is indicated as the most effective single agent for maximal debulking of skin disease. Radiotherapy also has an important role in the management of the less common CTCL, including the curative treatment of localised primary cutaneous anaplastic large cell lymphoma. Despite proven efficacy and quality of life benefits, disparity exists in access to RT and TSEBT. World-wide, stronger multidisciplinary collaborations and greater patient advocacy are required to increase access to RT and improve equity of care for our patients with CTCL.

Flexible real-time skin dosimeter based on a thin-film copper indium gallium selenide solar cell for electron radiation therapy

PURPOSE

Various dosimeters have been proposed for skin dosimetry in electron radiotherapy. However, one main drawback of these skin dosimeters is their lack of flexibility, which could make accurate dose measurements challenging due to air gaps between a curved patient surface and dosimeter. Therefore, the purpose of this study is to suggest a novel flexible skin dosimeter based on a thin-film copper indium gallium selenide (CIGS) solar cell, and to evaluate its dosimetric characteristics.

METHODS

The CIGS solar cell dosimeter consisted of (a) a customized thin-film CIGS solar cell and (b) a data acquisition (DAQ) system. The CIGS solar cell with a thickness of 0.33 mm was customized to a size of 10 × 10 mm² . This customized solar cell plays a role in converting therapeutic electron radiation into electrical signals. The DAQ system was composed of a voltage amplifier with a gain of 1000, a voltage input module, a DAQ chassis, and an in-house software. This system converted the electrical analog signals (from solar cell) to digital signals with a sampling rate of ≤50 kHz and then quantified/visualized the digital signals in real time. We quantified the linearity/ sampling rate effect/dose rate dependence/energy dependence/field size output factor/reproducibility/curvature/bending recoverability/angular dependence of the CIGS solar cell dosimeter in therapeutic electron beams. To evaluate clinical feasibility, we measured the skin point doses by attaching the CIGS solar cell to an anthropomorphic phantom surface (for forehead, mouth, and thorax). The CIGS-measured doses were compared with calculated doses (by treatment planning system) and measured doses (by optically stimulated luminescent dosimeter).

RESULTS

The normalized signals of the solar cell dosimeter increased linearly as the delivered dose increased. The gradient of the linearly fitted line was 1.00 with an R-square of 0.9999. The sampling rates (2, 10, and 50 kHz) of the solar cell dosimeter showed good performance even at low doses (<50 cGy). The solar cell dosimeter exhibited dose rate independence within 1% and energy independence within 3% error margins. The signals of the solar cell dosimeter were similar (<1%) when penetrating the same side of the CIGS cell regardless of the rotation angle of the solar cell. The field size output factor measured by the solar cell dosimeter was comparable to that measured by the ion chamber. The solar cell signals were similar between the baseline (week 1) and the last time point (week 4). Our detector showed curvature independence within 1.8% (curvatures of <0.10 mm^- ) and bending recovery (curvature of 0.10 mm^-1 ). The differences between measured doses (CIGS solar cell dosimeter vs. optically stimulated luminescent dosimeter) were 7.1%, 9.6%, and 1.0% for forehead, mouth, and thorax, respectively.

CONCLUSION

We present the construction of a flexible skin dosimeter based on a CIGS solar cell. Our findings demonstrate that the CIGS solar cell has a potential to be a novel flexible skin dosimeter for electron radiotherapy. Moreover, this dosimeter is manufactured with low cost and can be easily customized to various size/shape, which represents advantages over other dosimeters.

Development of transparent eye shields for total skin electron beam radiotherapy

Purpose

For total skin electron (TSE) beam radiation therapy, the anterior eye and conjunctiva can be protected with eye shields to prevent keratitis, xerophthalmia, and cataractogenesis. Conventional metal eye shields can reduce patient balance by obscuring vision and thus increasing the risk for falls. We report on the design, fabrication, and clinical use of transparent acrylic eye shields for TSE.

Methods

The primary design goals were a seven‐fold reduction in the dose to the anterior eye and conjunctiva to meet published dose‐recommendations, preservation of vision for the wearer, and biocompatibility for external use. Resembling thick swim goggles, the design features 23 mm thick acrylic lenses that are mounted in a 3‐D printed support structure that conforms to the eye socket and can be worn with a strap. Dose measurements were performed in a simulated Stanford‐technique treatment with an anthropomorphic phantom using Gafchromic EBT film

Results

The transparent eye shields were manufactured using a 3D‐printer and CNC‐machine. Based on measurements from the simulated treatments for each of the eye shields, the eye shields provided a 12‐fold reduction in dose to the lens. After use in more than 200 fractions, the shields were well tolerated by patients, and there were no reports of any incidents or adverse events.

Conclusion

Transparent TSE eye shields are able to reduce the dose to the eyes while maintaining vision during treatment at a reasonable cost.

Mycosis fungoides and Sézary syndrome: Australian clinical practice statement

Primary cutaneous lymphomas represent a heterogeneous group of T- and B-cell lymphomas with distinct clinical presentations, histopathologic features, treatment approaches and outcomes. The cutaneous T-cell lymphomas, which include mycosis fungoides and Sézary syndrome, account for the majority of the cutaneous lymphomas. This Clinical Practice Statement is reflective of the current clinical practice in Australia. An expanded form of the Clinical Practice Statement (and updates), along with helpful patient resources and access to support groups, can be found at the following (http://www.australasianlymphomaalliance.org.au).

Total skin electron beam therapy for primary cutaneous T-cell lymphomas: clinical characteristics and outcomes in a Mexican reference center

Aim

The aim of this study was to assess treatment modalities, treatment response, toxicity profile, disease progression and outcomes in 14 patients with a confirmed diagnosis of primary cutaneous T-cell lymphoma (PCTCL) treated with total skin electron beam therapy (TSEBT).

Background

Primary cutaneous lymphomas (PCLs) are extranodal non-Hodgkin lymphomas originating in the skin without evidence of extracutaneous disease at diagnosis. Despite advances in systemic and local therapy options, the management of advanced stages remains mostly palliative.

Materials and Methods

This is a retrospective study of patients with PCTCL, diagnosed and treated in a reference center in Mexico City, analyzing treatment modalities, response to treatment, long-term outcome, and mortality.

Results

Eight males (57%) and 6 (43%) females were identified. Most patients were stage IVA (n = 5, 36%) followed by stage IB and IIB (28.5% and 21.4%, respectively). Eleven patients received the low-dose RT scheme (12 Gy), 1 patient, the intermediate-dose RT scheme (24 Gy), and 2 patients, the conventional-dose RT scheme (36 Gy). Mean follow-up time was 4.6 years. At first follow-up examination, 6-8 weeks after radiotherapy, the overall response rate (ORR) for the cohort was 85%. The median PFS for the whole cohort was 6 months.

Conclusion

This study reinforces the role of TSEBT when compared with other treatment modalities and novel agents. Low-dose TSEBT is now widely used because of the opportunity for retreatment.

Cost of early-stage mycosis fungoides treatments in Spain

AIM

To identify the most common therapeutic options for the treatment of early-stage mycosis fungoides in Spain, quantify their associated healthcare resource use and costs.

METHODS

After reviewing the literature, a panel of 6 Spanish clinical dermatologists validated the treatments and healthcare resource use through a structured questionnaire. Individual responses were collected, analyzed and presented into a face-to-face meeting in order to reach a consensus. Cost categories considered were: drug acquisition and administration, photo/radiotherapy session and maintenance, clinical follow-up visits and laboratory tests. Costs were expressed in euros from 2018. The Spanish National Health System perspective was considered, taking into account direct health costs and time horizons of 1, 3 and 6 months.

RESULTS

Costs for the skin-directed treatments (SDT) assessed at 1, 3 and 6 months, were: Topical carmustine [€6,593.36, €19,780.09 and €27,592.78]; Phototherapy with psoralens and ultraviolet A light (PUVA) [€1,098.68, €2,999.99 and €3,187.60]; Narrow-band ultraviolet B phototherapy [€1,657.47, €4,842.10 and €4,842.10]; Total skin electron beam therapy (TSEBT) [€6,796.45, €7,913.34 and €7,913.34]. Cost for topical corticosteroids, being considered an adjuvant option, were €17.16, €51.49 and €102.97. Costs for the assessed systemic treatments alone or in combination with SDT at 1, 3 and 6 months, were: Systemic retinoids [€2,026.03, €5,206.63 and €7,426.42]; Systemic retinoids + PUVA phototherapy [€3,066.50, €8,271.26 and €10,046.58]; Interferon alfa + PUVA phototherapy [€1,541.09, €5,167.57 and €6,404.55].

CONCLUSION

According to the Spanish clinical practice, phototherapies in monotherapy were the treatments with the lowest associated costs regardless of the time horizon considered. TSEBT turned out as the treatment with the highest associated costs when considering 1 month. However, while considering 3 and 6 months the treatment with the highest associated costs was topical carmustine. The results of this analysis may provide critical information to measure the disease burden, to detect unmet medical needs and to advocate towards better treatments for this rare disease.

Lack of Durable Remission with Conventional-Dose Total Skin Electron Therapy for the Management of Sezary Syndrome and Multiply Relapsed Mycosis Fungoides

Mycosis fungoides (MF) and Sezary syndrome (SS) are multi-relapsing, morbid, cutaneous T-cell lymphomas. Optimal treatment sequencing remains undefined. Total skin electron therapy (TSE) is a highly technical, skin-directed treatment, uniquely producing symptom-free and treatment-free intervals. Recent publications favour low-dose TSE for reduced toxicity, but early data support conventional-dose TSE (cdTSE) for longer disease control. Patient selection requires weighing-up tolerability against response durability. We investigated duration of benefit from cdTSE in patients with poorer prognosis diseases: SS and heavily pre-treated MF. Endpoints were overall survival, and “time to next treatment” (TTNT) as surrogate for clinical benefit duration. Seventy patients (53 MF, 17 SS) were eligible: median prior treatments, 4; median cdTSE dose, 30 Gy; median follow-up, 5.8 years. SS patients had worse prognosis (HR = 5.0, p < 0.001) and shorter TTNT (HR = 4.5, p < 0.001) than MF patients; median TTNT was only 3.7 months. Heavily pre-treated MF patients had inferior prognosis (HR = 1.19 per additional line, p = 0.005), and shorter TTNT (HR = 1.13 per additional line, p = 0.031). Median TTNT for MF patients with ≥3 prior treatments was 7.1 months, versus 23.2 months for 0–2 prior treatments. In conclusion, cdTSE has a limited role in SS. TTNT is reduced in heavily pre-treated MF patients, suggesting greater benefit when utilized earlier in treatment sequencing.

Clinical outcomes and prognostic factors in patients with mycosis fungoides who underwent radiation therapy in a single institution

PURPOSE

We aimed to evaluate clinical outcomes including progression-free survival (PFS), overall survival (OS), partial response, and complete response in patients who underwent radiation therapy (RT) for mycosis fungoides (MF). Also, we sought to find prognostic factors for clinical outcomes. Materials and.

METHODS

Total 19 patients confirmed with MF between 1999-2015 were retrospectively reviewed. Clinical and treatment characteristics, clinical outcomes, and and toxicities were analyzed.

RESULTS

Eleven patients were treated with total skin electron beam radiotherapy (TSEBT) and 8 patients with involved field radiation therapy (IFRT) with median dose of 30 Gy, respectively. The median time interval from diagnosis to RT was 2.6 months (range, 0.4 to 87.3 months). The overall response rate was 100%; 11 patients (57.9%) had a complete response and 8 patients (42.1%) a partial response. The presence of positive lymph node at the time of consultation of RT was associated with lower OS (p = 0.043). In multivariate analysis, PFS was significantly lower for patients with increased previous therapies experienced following RT (p = 0.019) and for patients showing PR during RT (p = 0.044). There were no reported grade 3 or more skin toxicities related with RT.

CONCLUSION

Both IFRT and TSEBT are effective treatment for MF patients. Patients with short disease course before RT or complete response during RT are expected to have longer PFS. Positive lymph node status at the initiation of RT was associated woth poor OS, suggesting other treatment modalities such as low-dose RT for patients with low life-expectancy.

Total Skin Electron Beam Therapy in the Treatment of Mycosis Fungoides: A Review of Conventional and Low-Dose Regimens

Mycosis fungoides (MF) is the most prevalent subtype of cutaneous T-cell lymphoma, which is characterized by the proliferation of CD4⁺ T cells. While often an indolent disease, most patients eventually develop progression from isolated patches to tumors and finally nodal or visceral involvement. Treatment choice is largely based on disease burden, though prognostic factors such as disease stage, patient age, and extracutaneous involvement must be taken into consideration. Radiotherapy represents one of the most effective therapeutic modalities in the treatment of MF. Lymphocytes are exquisitely radiosensitive, and excellent responses are observed even with low doses of radiation. Total skin electron beam therapy (TSEBT) is a special technique that allows for the homogenous irradiation of the entire skin. There are well-documented radiation dose-response relationships for achieving a complete response. As such, TSEBT doses ≥ 30 Gy comprise the current standard of care. Although highly effective, most patients experience recurrent disease even after conventional-dose (≥ 30 Gy) TSEBT. In addition, toxicity is cumulatively dose dependent, and there is reluctance to administer multiple courses of conventional-dose TSEBT. Consequently, there has been renewed interest in determining the utility of TSEBT at lower total (≤ 30 Gy) doses. Advantages of low-total-dose (with standard dose per fraction) TSEBT include a shortened treatment course, the potential to minimize the risk of adverse events, and the opportunity to allow for retreatment in cases of disease recurrence. This comprehensive review compares the impact of different TSEBT dosing schemes on clinical outcomes of MF.

Clinical results of the total skin electron irradiation of the mycosis fungoides in adults. Conventional fractionation and low dose schemes

BACKGROUND

Mycosis fungoides (MF) is a rare skin condition, effectively treated by irradiation. Since 1951, different methods of total skin irradiation have been developed. Although dose-response effect has been demonstrated in many publications, controversies about low dose treatment still exist.

AIM

The analysis of results of the total skin electron irradiation (TSEI), especially low dose TSEI in comparison with standard dose treatment is the subject of this review. Also, acute and late side effects of radiotherapy in MF are discussed.

MATERIALS AND METHODS

Medline search and analysis of studies published between 1995 and 2012, containing key words: mycosis fungoides, standard dose TSEI, low dose TSEI, total skin electron beam therapy (TSEBT).

RESULTS

Detailed analysis of relevant studies demonstrated that standard dose radiotherapy 30-36 Gy is the most effective treatment used in clinical practice. Objective response rate (ORR) is high, especially for less advanced stages of disease. Complete response rate (CR), although slightly lower, is still relatively high. For more advanced MF, TSEI serves as a very good method of palliative treatment and relief of symptoms, like pruritus, pain or desquamation. There is no consensus regarding low dose TSEI; the method is widely accepted as a palliative treatment or in case of reirradiation.

CONCLUSIONS

Standard dose TSEI is an effective method of MF treatment for radical and palliative treatment, producing high rate of ORR and reasonably long time to progression (TTP). Acute and late side effect of treatment are mostly mild and easy to manage. Low dose TSEI is still in the phase of clinical studies.

Advantages and implications of high dose rate (HDR) total skin electron irradiation (TSEI) for the management of Mycosis Fungoides. Indian experience

BACKGROUND

Mycosis Fungoides (MF) is an indolent lymphoproliferative disorder affecting dermis caused by abnormal proliferation of CD4+ T-cells. Radiation therapy is the most effective modality of treatment for MF which offers cure in limited stage disease and desirable palliation in advance stage disease. Treating entire skin having many curved surfaces and folds with radiation is the real challenge for the radiation oncologist. Many techniques, dose schedules and modifications in total skin electron irradiation (TSEI) have been tried since 1950s. TSEI treatment is a very time consuming, inconvenient and physically challenging to both patient as well as oncologist.

AIM

At our center TSEI was performed since 1983 with conventional linear accelerator where the treatment time was prolonged beyond two hours, which was very difficult or the patient, oncologist, technical officer and eating away the machine time hampering the treatment of other patients. From 1998 we shifted to high dose rate (HDR) mode, in order to bring down the treatment time of a single patient every day from two and half hour to 15 min. The reduction of treatment time increases patient compliance and at the same time saved machine time.

MATERIALS AND METHODS

Between 1998 and 2003, eleven pathological diagnosed MF patients were treated using HDR TSEI. All the patients were male between 40 and 70 years of age, who had the history of having the disease for 7-22 months. Four patients had T2 and seven patients had T3 stage disease with more than 90% skin surface involvement. TSEI was performed with 4 MeV electrons with a daily fraction size of 120 cGy to a total dose of 36 Gy. At the end of 36 Gy, boost dose of 10 Gy was delivered to self shielding regions like sole, scalp and perineum. Considering the treatment related toxicities and consequent treatment interruptions, in the first seven patients, the last four patients were treated using similar HDR TSEI technique with modified treatment schedule, where the treatment was given on an alternate day basis following 2nd week of initiation of treatment.

RESULTS

The patients were followed over a period of 144 months with a median of 72 months. Nine patients are alive without any evidence of disease, one patient relapsed and one died due to progression of disease. The most common radiation related morbidities are erythema, skin blisters, various degree of desquamations, swelling of joints (specially small joints) etc. which are controlled by treatment interruptions and conservative measures. By modifying the treatment schedule, the incidence of toxicity as well as treatment interruptions were brought down.

CONCLUSIONS

We can conclude that HDR-TSEI is an excellent and safe therapeutic modality for the patients with MF both curative as well as palliative without any added toxicity profile, provided patient positioning is done properly.

Ethics of clinical trials in dermatology

The ethics of clinical trials have been the subject of numerous previous publications and mandates that are used by institutional review boards on an everyday basis. The protection of human rights and the sanctity of informed consent are critical components of clinical research monitored by human subjects investigation committees throughout our profession. In this contribution, the everyday conflicts of interest that can compromise clinical research in dermatology are presented in a case format. Of utmost importance, the primary interest of the investigating dermatologist should always be the patient at hand and those who could benefit from the research. Navigating the turbulence created by finances, academia, and corporate America is critical. By presenting several case scenarios within the relatively rare disease arena of cutaneous T-cell lymphoma, these conflicts can be appreciated. Consequently, understanding these influences in one disease setting permits generalizations to be applied to any dermatologic clinical research.

Total skin electron beam therapy for cutaneous T-cell lymphoma: a nationwide cohort study from Denmark

BACKGROUND

Total skin electron beam therapy (TSEBT) is an effective palliative treatment for cutaneous T-cell lymphoma (CTCL). In the present study we reviewed the clinical response to TSEBT in Danish patients with CTCL.

MATERIAL AND METHODS

This retrospective study included 35 patients with CTCL treated with TSEBT in Denmark from 2001 to 2008 and followed for a median time of 7.6 months (range 3 days-3.7 years). Twenty five patients were treated with high-dose (30 Gy) and 10 patients in a protocol with low-dose (4 Gy) TSEBT.

RESULTS

Patients treated with low-dose therapy had inadequate response to treatment compared to patients treated with high-dose. Consequently the study with low-dose was discontinued and published. In patients treated with high-dose the overall response rate was 100%. Complete response (CR) rate was 68% and CR occurred after a median time of 2.1 months (range 1.8 months-2.0 years). We found no difference in CR rate in patients with T2 (66.7%) and T3 disease (78.6%) (p = 0.64). Following CR 82.4% relapsed at a median time of four months (range 12 days-11.5 months). Relapse-free-survival was similar in patients with T2 and T3 disease (p = 0.77). Progressive disease (PD) was experienced in 28.0% and the median time to PD was 9.0 months (range 4.6-44.3 months). Overall progression-free survival was 95.3%, 72.1% and 64.1% after 0.5-, 1- and 2-years. Effects of initial therapy on TSEBT treatment response and side effects to TSEBT were also analyzed.

CONCLUSION

In conclusion, the present study confirms that high-dose TSEBT is an effective, but generally not a curative therapy in the management of CTCL. High-dose treatment yielded significantly better results than low-dose treatment with 4 Gy. TSEBT offers significant palliation in most patients when other skin-directed or systemic treatments have failed.

Total scalp radiation using image-guided IMRT for progressive cutaneous T cell lymphoma

Modern radiotherapy has advanced dramatically over the past decade and it is now possible to focus radiotherapy with extreme precision. This allows the radiation dose to be targeted to the area(s) of tumour while sparing adjacent normal tissues even in seemingly complicated and difficult parts of the body. The case report presented here will illustrate how it is possible to irradiate the entire scalp for extensive cutaneous T cell lymphoma while minimising radiotherapy to the underlying brain, orbits and other critical structures.

Total skin electron irradiation treatment for mycosis fungoides with a new alternate daily treatment schedule to minimize radiation-associated toxicity: a preliminary experience

Conventional total skin electron irradiation (TSEI) for mycosis fungoides (MF) causes radiation toxicity, requiring treatment interruptions that prolong the treatment period, making patient compliance poor. We evaluated an alternate daily treatment schedule of TSEI, using a high dose rate (HDR) to minimize radiation toxicity and shorten the treatment duration. Four patients (aged 45-73 years with MF duration of 7-22 months) were treated by TSEI using HDR. The treatment was given on 5 days/week for 2 weeks followed by treatment on alternate days to deliver a total dose of 36 Gy. All the patients completed treatment in 10 weeks and had complete remission. Radiation toxicity was much less common with this schedule, requiring no treatment interruption. All the patients were until in remission after 60-84 months of follow-up. This schedule of TSEI treatment caused minimal radiation toxicity and allowed completion of treatment over a shorter period, giving good clinical remission and prolonged disease-free survival.

[Total skin electron beam therapy for early-stage mycosis fungoides: immediate results and long-term follow-up in 68 patients]

BACKGROUND

Our aim was to evaluate the efficacy of total skin electron beam therapy (TSEB) in the management of early-stage mycosis fungoides in order to assess its position in relation to other skin-directed therapies.

PATIENTS AND METHODS

A retrospective study of 68 patients (30 in stage T1 and 38 in stage T2).

RESULTS

The median treatment duration was 6 weeks. Three months after the end of TSEB, a complete clinical response occurred in 66 patients (97%). The most marked effects of acute toxicity included localized ulcerations in 13 patients (13.2%) not requiring hospitalization. Mean follow-up was 6.5 years (1.6 to 28.7). The overall survival rates at 5 and 10 years were 86% and 71%, respectively. Thirty-nine patients (57.4%) experienced relapse with a mean disease-free interval of 1.8 years. The disease-free survival rates at 5 and 10 years were 41% and 31%, respectively. This rate was higher when TSEB was performed early (p=0.031). Twenty-one years after TSEB, only one case of cutaneous malignancy (basal cell carcinoma) was noted.

DISCUSSION

Because of its high response rates and rapidity of action, TSEB should be considered as first-line therapy in the management of early-stage mycosis fungoides.

Mycosis fungoides

Mycosis fungoides (MF) constitutes the most frequent cutaneous T-cell lymphoma. Sezary syndrome is considered by some authors to be an erythrodermic leukemic variant of MF, but is classified separately in the new WHO-EORT classification of cutaneous lymphomas. MF usually occurs in old adults with a 2:1 male to female ratio. Its prognosis is variable and strongly conditioned by the extent and type of skin involvement and presence of extracutaneous disease. Patients with stage IA-disease have an excellent prognosis with an overall long-term life expectancy that is similar to an age-, sex-, and race-matched control population. Almost all patients with stage IA MF will die from causes other than MF, with a median survival >33 years. Only 9% of these patients will progress to more extended disease. Patients with stage IB or IIA have a median survival greater than 11 years. These patients with T2 disease have a likelihood of disease progression of 24% and nearly 20% die of MF. Subgroups with stage IB or IIA have similar prognosis. Patients with cutaneous tumors or generalized erythroderma have a median survival of 3 and 4.5 years, respectively. The majority of these patients will die of MF. Extracutaneous dissemination is observed in less than 10% of patients with patch or plaque disease and in 30-40% of patients with tumors or generalized erythrodermatous involvement. Extracutaneous involvement is directly correlated to the extent of cutaneous disease. The most commonly involved organs are lung, spleen, liver, and gastrointestinal tract. Patients with extracutaneous disease at presentation involving either lymph nodes or viscera have a median survival of <1.5 years. Patients with plaque-type or erythrodermic MF may develop cutaneous tumors with large cell histology, often expressing CD30, which share a common clonal origin as observed in their preexisting MF and are associated with a less favourable outcome.

Cutaneous Lymphomas

The skin is the most common site of extranodal non-Hodgkin lymphoma, with a yearly incidence approaching 1 per 100,000 individuals in the United States. Skin lymphomas are classified broadly into cutaneous T-cell lymphoma (CTCL) and cutaneous B-cell lymphoma (CBCL). Within these broad categories, multiple unique pathologic entities exist with a wide array of natural histories and treatment options. Radiotherapy plays an important role in the curative treatment of localized CTCL and CBCL and may be used to palliate cutaneous and visceral symptoms associated with advanced disease. This review highlights the role of radiotherapy in the multidisciplinary management of cutaneous lymphoma.

Central Neurologic Involvement in Mycosis Fungoides

BACKGROUND

Neurologic involvement in mycosis fungoides is rare. Isolated case reports in the literature suggest the pattern and the natural history for such occurrences, while a literature summary can provide direction on diagnosis and management. Although case series may confirm such information, cohort data are required to establish an overall risk of occurrence and to evaluate possible predictive factors.

METHODS

We presented a case of central nervous system involvement in mycosis fungoides from Haifa, Israel and tabulated a series of nine cases from Canada. To estimate the risk of neurologic involvement, a cohort of 680 consecutive patients with newly diagnosed mycosis fungoides, of which the nine cases of neurologic involvement emerged during follow up, was analyzed using the Kaplan-Meier method. The actuarial risk of developing neurologic involvement was related to the baseline tumor-node-metastasis-blood classification factors.

RESULTS

The pattern of disease in these 10 additional cases confirms the overall pattern in the approximately 40 patients described in the literature. The main symptoms are fluctuating higher cognitive functions and cranial nerve dysfunction, with fairly rapid clinical onset of symptoms. Most cases of central neurologic involvement with mycosis fungoides emerge within a setting of advanced disease. In patients with newly diagnosed mycosis fungoides, the greatest risk of developing neurologic involvement is within the first several years after diagnosis and is associated with the initial stage of disease. Patients with two or more of the T3-4, N3, M1, and B1 classification factors have a one in six chance of developing central neurologic involvement, while there is about a one in a hundred chance for the corresponding control group.

CONCLUSIONS

Neurologic involvement with mycosis fungoides is indeed rare, but it is associated with a more advanced stage at diagnosis and with other visceral disease that can precede it. Although the role of low-dose prophylactic cranial radiation is uncertain, overt neurologic involvement requires urgent palliative treatment.

Ultimate results of radiation therapy for T1-T2 mycosis fungoides (including reirradiation)

PURPOSE

We report on our experience in the treatment of T1 and T2 mycosis fungoides (MF) with total skin electron beam therapy (TSEBT), with respect to relapse-free rate, overall survival rate, and management of recurrence.

METHODS AND MATERIALS

Between 1975 and 2001, 141 patients with MF were referred to the radiotherapy department for treatment by TSEBT. A total of 57 patients were staged as having T1 or T2 disease (24 T1 and 33 T2 patients). A total of 25 received topical therapy before irradiation. Treatment was delivered through a 6-MeV linear accelerator to a mean total dose of 30 Gy, 2 Gy/day, 4 days/week, for 4 weeks. Close follow-up was initiated without adjuvant therapy. Median age was 61 years (range, 19-84), and median follow-up was 114 months (range, 14-300).

RESULTS

Three months after completion of TSEBT, the overall response rate was 94.7%. A complete response was achieved in 87.5% of T1 and 84.8% of T2 patients. Thirty-one patients (54.4%) experienced a skin failure (8 with T1 and 23 with T2 disease) within 1 year. Eighteen patients of 31 received a reirradiation as salvage therapy (6 localized treatment with segmental fields of electron beam irradiation and 12-second TSEB delivering 24 Gy in 12 fractions). Two were treated by topical steroids, and 11 received combination therapy with PUVA (2/10), topical (10/10) or systemic (4/10) chemotherapy, or interferon (7/10). After a second course of TSEBT (4 T1 and 10 T2 patients), the 5-year freedom from relapse rate was 70% vs. 39% in patients having received other modalities. For the whole group, 5-year DFS was 50%. The 5/10/15-year OS were 90%/65%/42%, respectively. In univariate analysis, T1 (p = 0.03), CR after first TSEBT (p = 0.04), and age younger than 60 (p < 0.001) were significant prognostic factor for OS. In multivariate analysis, age younger than 60 years was statistically associated with improved OS (p = 0.001); T stage and completion of CR remained under threshold of significance (p = 0.059 and p = 0.063, respectively). During the mean 86-month period of follow-up from relapse, a second recurrence was observed in 29% of patients.

CONCLUSIONS

TSEBT is highly effective in early-stage MF without adjuvant therapy. Management of relapses with local radiotherapy or second TSEBT is feasible, time-saving, and cost-effective.

Management of the primary cutaneous lymphomas

Cutaneous lymphomas are rare and, although some are a manifestation of systemic lymphoma, the majority arise primarily from the skin. These primary cutaneous lymphomas comprise both T- and B-cell subtypes and represent a wide spectrum of disorders, which at times can be difficult to diagnose and classify. Classical therapeutic strategies include topical corticosteroids, phototherapy, radiotherapy, retinoids, extracorporeal photopheresis, topical chemotherapy, systemic chemotherapy and biological response modifiers. Newer therapies include the synthetic retinoid bexarotene, the immunotoxin conjugate denileukin diftitox, interleukin-12 and monoclonal antibodies such as alemtuzumab and rituximab.

Total skin electron beam radiotherapy for patients who have mycosis fungoides

It has taken four decades of basic and clinical research to bring about a consensus process and published report that recognize a TSEB radiotherapy technique that is optimized from several perspectives (see references [2-4, 13]). Short and long-term clinical results with consensus TSEB radiotherapy technique are good. The therapeutic ratio of TSEB radiotherapy is well-defined and is clinically acceptable. Meanwhile, adjuvant PUVA and ECP may significantly improve results, but further data are needed to confirm these preliminary findings (see references [23, 34, 39, 40, 42]).

Mycosis fungoides: radiation therapy

Radiation therapy is the most effective single agent for the treatment of mycosis fungoides. There are well-defined dose-response relationships for achieving a complete response as well as the durability of this response. Techniques of electron beam therapy have been developed that permit treatment of the entire skin. Total-skin electron beam therapy is an important form of management, especially for patients who have thick generalized plaque or tumorous disease. Radiation therapy may also be used selectively for treatment of extracutaneous disease.

Analysis of long-term outcomes of combined modality therapy for cutaneous T-cell lymphoma

BACKGROUND

Although cutaneous T-cell lymphoma (CTCL), including mycosis fungoides (MF) and Sézary syndrome, is often responsive to treatment, few current therapies increase survival or consistently induce durable remissions, especially in advanced disease.

OBJECTIVE

In an effort to improve treatment efficacy and outcome in CTCL, a combined modality protocol using 3 to 4 consecutive phases of therapy was initiated in 1987 at M.D. Anderson Cancer Center, Houston, Tex.

METHODS

During a period of 15 years between 1987 and 2001, 95 patients with early-stage (Ia-IIa, n = 50) and late-stage (IIb-IVb, n = 45) MF were treated with subcutaneous interferon-alpha and oral isotretinoin, followed by total-skin electron beam therapy, and long-term maintenance therapy with topical nitrogen mustard and interferon-alpha. Patients with late-stage (IIb-IVb) disease also received 6 cycles of combination chemotherapy before electron beam therapy.

RESULTS

Combined modality therapy yielded a response rate of 85% with a 60% complete response rate. Among 38 patients with early-stage disease and 18 patients with late-stage disease achieving complete response, 9 (24%) patients with early-stage MF and 3 (17%) patients with late-stage MF achieved sustained remissions lasting more than 5 years. The median disease-free survival (DFS) for early and late stages of disease was 62 and 7 months, with 5-year Kaplan-Meier estimated rates of 50% and 27%, respectively. Current median overall survival times on combined modality are 145 months for patients with early-stage disease and 36 months for those with late-stage disease. Death was attributable to CTCL disease in 17 (55%) of 31 cases. The Kaplan-Meier estimates for 5-year survival are 94% for early-stage and 35% for late-stage disease. Univariate survival analysis in this patient population reveals statistically significant associations of clinical stage with overall response rates (P =.02), DFS (P =.03), and overall survival (P <.0001); age with DFS (P =.001) and overall survival (P =.04); and T stage (P <.0001) and lactate dehydrogenase (P =.007) with overall survival. By multivariate analysis using a Cox proportional hazards model, only age was significantly associated with DFS (hazard ratio 2.9), and only stage with overall survival (hazard ratio 18.2).

CONCLUSION

This nonrandomized and uncontrolled CTCL study gives supportive evidence that this multiphased combined modality regimen is well tolerated and may yield higher response rates and DFS than total-skin electron beam therapy alone, but provides no evidence for a change in survival.

Total skin electron irradiation in mycosis fungoides: comparison between a modified Christie Hospital translational technique and the Stanford technique

Seventy-one patients with mycosis fungoides (MF) were treated by Total skin electron irradiation (TSEI) using either a modified Christie Hospital translational technique (44 pts) or a six dual-field Stanford technique (27 pts). There was no statistical difference in response rate, disease-free survival and overall survival between the two irradiation techniques. However, the Stanford technique was significantly less toxic than the modified Christie Hospital technique.

Total skin electron radiation in the management of mycosis fungoides: Consensus of the European Organization for Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Project Group

Radiotherapy has been successfully implemented in the treatment of mycosis fungoides (MF) for almost a century. With the development of the modern linear accelerator, it has become possible to treat extended areas of the skin with accelerated electrons. Total skin electron beam radiation (TSEB) has been in use for several decades, and a number of technical modifications have been made with the goals of optimizing dose distribution and improving clinical outcome. Emerging evidence from recent studies suggests an association between TSEB techniques and efficacy in the treatment of MF. Based on this evidence, the European Organization for Research and Treatment of Cancer Cutaneous Lymphoma Project Group, in association with experts from radiotherapy centers in North America, has reached a consensus on acceptable methods and clinical indications for TSEB in the treatment of MF. The aims of this report are to enhance accessibility of this highly efficacious treatment modality to patients with MF and to provide a point of reference for further clinical research.

Treatment of cutaneous T cell lymphoma: current status and future directions

The treatment of cutaneous T cell lymphoma (CTCL), which includes mycosis fungoides and Sezary syndrome, has been in a state of continual change over recent decades, as new therapies are constantly emerging in the search for more effective treatments for the disease. However, prognosis and survival of patients with CTCL remains dependent upon overall clinical stage (stage IA-IVB) at presentation, as well as response to therapy. Past therapies have been limited by toxicity or the lack of consistently durable responses, and few treatments have been shown to actually alter survival, especially in the late stages of disease. Even aggressive chemotherapy has not been shown to improve overall survival compared to conservative sequential therapy in advanced disease, and adds the risk of immunosuppressive complications. Over the last decade, extracorporeal photopheresis has been the only single treatment that has been shown to improve survival in patients with Sezary syndrome, although its true efficacy and place in combination therapy remain unclear. Much of the focus of current research has been on combinations of skin-directed therapies and biological response modifiers, which improve response rates. The results of various trials over the years have also brought into favor the use of post-remission maintenance therapy with topical corticosteroids, topical mechlorethamine (nitrogen mustard), interferon-alpha, or phototherapy to prevent disease relapse. Recent novel developments in CTCL therapy include oral bexarotene, a retinoid X receptor-selective retinoid that has activity in all stages of CTCL, and the topical gel formulation of bexarotene, which plays a role in treating localized lesions. US Food and Drug Administration (FDA)-approved, oral systemic bexarotene has the advantage of a 48% overall response rate at a dosage of 300 mg/m(2)/day, and avoids immunosuppression and risk of central line and catheter-related infectious complications that are associated with other systemic therapies. Monitoring of triglycerides and use of concomitant lipid-lowering agents and thyroid replacement is required in most patients. Also recently FDA-approved, denileukin diftitox is the first of a novel class of fusion toxin proteins and is selective for interleukin-2R (CD25+) T cells, targeting the malignant T cell clones in CTCL. Denileukin diftitox is associated with capillary leak syndrome in 20 to 30% of patients, which may be ameliorated by hydration and corticosteroids. Higher response rates are possible by combining bexarotene with "statin" drugs and active CTCL therapies. Studies are being conducted on combining bexarotene and denileukin diftitox with other modalities. Biological response modifier therapies that are in current or future investigational trials include topical tazarotene, pegylated interferon, interleukin-2, and interleukin-12. At the forefront of systemic chemotherapy development, pegylated liposomal doxorubicin, gemcitabine, and pentostatin appear to have the greatest potential for success in CTCL therapy. Bone marrow transplantation, which is currently limited by the risk of graft-versus-host disease, offers the greatest potential for disease cure. Further developments for CTCL may include more selective immunomodulatory agents, vaccines, and monoclonal antibodies.

Total skin electron radiation for patients with erythrodermic cutaneous T-cell lymphoma (mycosis fungoides and the Sézary syndrome)

BACKGROUND

There is limited published evidence regarding the efficacy of total skin electron beam radiation for patients with the diffuse erythrodermic form of mycosis fungoides.

METHODS

Forty-five patients with erythrodermic mycosis fungoides were managed at McMaster University in Hamilton, Ontario, Canada (n=34), and at Yale University (n=11) between 1970 and 1996. All received radiation without neoadjuvant, concomitant, or adjuvant therapies. The median age was 67 years (range, 42-84 years). The male-to-female ratio was 2.2. Fifteen received radiation for the treatment of newly diagnosed disease. There were 28 with Stage III (T4 N0-1 M0), 13 with Stage IVA (T4 N2-3 M0), and 4 with Stage IVB (T4 N0-3 M1) disease, and 21 had blood involvement. The median radiation dose was 32 gray (Gy) (range, 4.8-40 Gy). The median treatment time was 21 days (range, 3-125 days). A technically more intense method of radiation (32-40 Gy and 4-6 MeV electrons) was administered to 23 patients.

RESULTS

All patients responded. The rate of complete cutaneous remission was 60%, with 26% remaining progression free at 5 years. Remission was associated with more intense radiation (P=0.014 in multivariate analysis with adjustment for blood and staging information). With the more intense radiation, 74% attained remission, with 36% remaining progression free at 5 years. For 8 patients with Stage III disease without blood involvement, all entered remission, with 69% remaining progression free at 5 years. Twenty of 30 deaths were related to mycosis fungoides. The median overall survival was 3.4 years, with a 10-year estimate of 28%. The median cause specific survival was 5 years, with a 10-year estimate of 43%. Both overall and cause specific survival were associated with an absence of blood involvement (both P<0.03 in multivariate analysis). Age was not a significant factor. Toxicities of radiation were acceptable when radiation was administered over 6-9 weeks at 5 fractions per week.

CONCLUSIONS

Total skin radiation is an efficient monotherapy for patients with erythrodermic mycosis fungoides. With more intense radiation, the rate of cutaneous remission is 74%, and 27% remain progression free at 10 years. Radiation may be most efficacious in Stage III, with no blood involvement. When there is blood, lymph node, or visceral involvement, combined modality therapies should be explored.

Radiotherapy in the management of mycosis fungoides: indications, results, prognosis. Twenty years experience

PURPOSE

To determine the role of total skin electron beam therapy (TSEBT) and the prognosis of patients with mycosis fungoides.

MATERIALS AND METHODS

From 1978 to 1996, 66 consecutive patients with mycosis fungoides received 30 Gy TSEBT delivered in 12 fractions over 40 days as treatment of their relapsed after topical or/and systemic therapy. All patients were staged as follows: stage A, superficial lesions covering less than 50% of the body surface; stage B, superficial lesions covering more than 50% of the body surface; Stage C. tumors involving the skin, lymph nodes and/or visceral organs.

RESULTS

The median age was 50 years (ranging from 13-78 years). There were 39 males and 27 females. The minimum follow-up was 12 months (range 12-192 months). There were 24 (36%) stage A patients, 22 (33%) stage B patients, and 20 (30%) stage C patients. The overall survival at 5 years for our series was as follows: 93% for stage A; 79% for stage B, and 44% for stage C disease (P = 0.002). For the entire cohort, the complete remission rate was 65%, the progression-free survival (PFS) at 5 years and 10 years was 30 and 18% respectively. For the group A, PFS was 62% at 5 years and 46% at 10 years; for group B, PFS was 19% at 5 years.

CONCLUSIONS

This study suggests that TSEBT gives good results for relapsed stage A disease. Total skin electron beam therapy combined with local fields irradiation or other local treatment (puvatherapy or topical nitrogen mustard) might further improve permanent complete response for stage B patients. The most advanced stages of mycosis fungoides are not controlled by TSEBT, but the radiation therapy offers good palliation results.

Total skin electron beam therapy with or without adjuvant topical nitrogen mustard or nitrogen mustard alone as initial treatment of T2 and T3 mycosis fungoides

PURPOSE

To compare the efficacy of total skin electron beam therapy (TSEBT) with or without adjuvant topical nitrogen mustard (+/- HN2) with topical nitrogen mustard (HN2) alone as initial management of T2 and T3 mycosis fungoides (MF).

METHODS AND MATERIALS

A retrospective analysis of 148 patients presenting to Stanford from January, 1970 through January, 1995 within 4 months of pathologic diagnosis of MF. Fifty-five patients with T2 and 27 with T3 disease received TSEBT +/- HN2. Fifty-four patients with T2 and 12 with T3 disease received HN2 alone. Boosts with radiotherapy were usually administered to cutaneous tumors of patients with T3 disease.

RESULTS

TSEBT +/- HN2 yielded significantly higher complete response (CR) rates than did HN2 alone in patients with T2 and T3 disease (76% vs 39%, p = 0.03 for T2, and 44% vs 8%, p < 0.05 for T3, respectively). In T2 disease, treatment with adjuvant HN2 was associated with a longer freedom from relapse following TSEBT when compared to observation following a CR to TSEBT (p = 0.068). However, no significant differences in survival were observed for different management programs for T2 or T3 disease. In T2 disease, both TSEBT and HN2 were as effective as salvage therapy as when utilized as initial therapy. However, salvage therapy in T3 disease was rarely effective. Limited tumor involvement in T3 disease did not correlate with improved survival compared to more generalized tumorous disease. MF contributed to 27% and 68% of deaths in patients with T2 and T3 disease, respectively.

CONCLUSION

Because of high response rates, management of significantly symptomatic or extensive T2 MF should include TSEBT, and adjuvant HN2 should be administered after a CR to TSEBT. Patients with T2 disease who fail TSEBT or HN2 can be salvaged with the other modality. TSEBT is also an effective treatment for T3 disease. The small subset of patients with limited T3 disease may also be treated with HN2 and local radiotherapy to the tumors. Further investigations are necessary to improve the overall outcome for T3 mycosis fungoides.

[Radiotherapy of cutaneous lymphomas]

Radiotherapy plays an important role in the treatment of cutaneous lymphomas. In the treatment of Mycosis fungoides, total skin electron beam radiation therapy is efficient for patients with limited and superficial forms of the disease. Radiotherapy is also efficient for the locally advanced forms of non-epidermotropic lymphomas. The palliative radiotherapy is indicated for advanced, nodular and treatment resistant forms of cutaneous lymphomas and for voluminous lymphadenopathies.

[Radiotherapy and skin tumors]

Radiotherapy plays an important role in the treatment of skin tumours. For skin carcinomas, external irradiation (kilovoltage X-rays or electrons according to clinical characteristics) is more valuable than interstitial brachytherapy, which is recommended for tumours of the lip and of the nasal vestibule. In mycosis fungoides, total cutaneous electron beam radiation therapy is efficient for patients with limited superficial plaques. In the classical form of Kaposi's sarcoma, radiotherapy can achieve local control whereas it obtains good palliative results in the epidemic form.

[Cutaneous lymphoma in Tunisia: clinical profile and therapeutic results]

PURPOSE

The aim of this retrospective study was to investigate therapeutic result of cutaneous lymphoma in Tunisia.

PATIENTS AND METHODS

Between January 1969 and June 1994, 100 patients with cutaneous lymphoma were referred either to Salah Azaiz Institute or the other University Hospitals of Tunisia. Fifty-one patients had epidermotropic lymphoma and 49 non-epidermotropic lesions. Eighty-seven patients received complete treatment. Puvatherapy and other local dermatologic treatments were used for early stage mycosis fungoïdes. Thirty-two patients benefited from radiotherapy, with curative dose in 28 cases. Chemotherapy including anthracyclin agents was used for high grade lymphoma. Thirteen patients had association of radiotherapy and chemotherapy.

RESULTS

Five-year survival rates were 50% for patients with epidermotropic lesions and 56% for patients with non-epidermotropic cutaneous lymphoma. Statistical study has not identified any significant prognosis factor.

CONCLUSION

Radiotherapy and chemotherapy are both effective. Treatment should depend on stage and histologic type.

The role of radiotherapy in the treatment of lymphoma and thymoma

Chemotherapy is the mainstay of therapy for the treatment of lymphoma in dogs and cats. Radiation therapy can be utilized in the management of patients with solitary lymphoma and to induce a rapid local response in selected patients with multicentric lymphoma. A combination of surgery and radiation therapy can offer an excellent prognosis for cats with thymoma. Radiation therapy can also play a role in the management of dogs with thymoma.

Management of cutaneous lymphoma

The foregoing underlines the advances which have been made in our understanding of cutaneous lymphoma and the areas where further research is needed. With a few noteable exceptions the aim of therapy in CTCL is palliative rather than curative and treatment success is measured in terms of disease-free interval. There is still no evidence that any chemotherapeutic regimen prolongs survival. A possible exception is the effect of photopheresis in Sézary syndrome but our own experience differs from that in the USA and underlines the need to identify patients with clonal disease when defining subjects for study. The combination of genotypic analysis and new treatment methods offers exciting new prospects in the management of patients with cutaneous lymphoma.

Additional courses of total skin electron beam therapy in the treatment of patients with recurrent cutaneous T-cell lymphoma

BACKGROUND

Recurrent cutaneous T-cell lymphoma (CTCL) is managed with a variety of modalities. Repeat treatment with additional courses of total skin electron beam therapy (TSEBT) has not been formally evaluated.

OBJECTIVE

Our purpose was to evaluate the efficacy and toxicity of additional TSEBT for recurrent CTCL.

METHODS

A total of 14 patients were treated with TSEBT and received at least two courses, with five of those patients receiving a third course. Patients were offered additional TSEBT if they suffered recurrence despite other therapy if the extent of the recurrence precluded localized radiation. The median follow-up was 36 months.

RESULTS

The median dose for the entire group was 57 Gy. Thirteen patients (93%) achieved a complete response (CR) after the initial course. After the second course, 12 patients (86%) had a CR; of the five patients who underwent a third course, three (60%) achieved a CR. The median disease-free interval after the first course of therapy for those with a CR was 20 months and 11.5 months after the second course. Median survival after the second course was 15 months. All patients had xerosis, pruritus, desquamation, mild erythema, epilation, and anhidrosis of the skin.

CONCLUSION

Patients with recurrent CTCL recalcitrant to other forms of therapy or too diffuse for treatment with localized radiation fields are candidates for additional TSEBT. This therapy is effective and well tolerated with an acceptable risk profile.

Implementation of total skin electron therapy using an optional high dose rate mode on a conventional linear accelerator

A technique for total skin electron therapy (TSET) has been implemented using a standard accelerator that has been equipped with an optional special procedures mode to permit high dose-rate therapy with a 6-MeV electron beam. Patients are treated in a standing position using dual angled fields at a source to skin distance of 3.6 m. Dosimetric characteristics of the dual field technique were investigated for the 6-MeV beam as well as for a lower energy beam produced by the introduction of an acrylic beam degrader. A treatment stand, which incorporates the degrader in addition to devices used for patient support and shielding, is described. Acceptable beam uniformity and depth dose have been achieved while maintaining a low level of x-ray contamination. Treatment times are reasonably short since the output of the machine in the high-dose-rate mode is 25 Gy/min at the isocenter. Beam uniformity, dose rate, and x-ray contamination are relatively unaffected by the presence of the beam degrader if it is positioned near the treatment plane. The high dose-rate electron option is a useful treatment mode that provides the advantage of reduced treatment times while retaining proper functioning of all accelerator dosimetry systems and interlocks. Use of a dual field technique permits TSET in a treatment room of standard dimensions. The machine is easily set up for treatment, and patient setup is simplified through use of a customized support system.