Scalp Irradiation Research Articles

SU-GG-T-573: Total Scalp Irradiation: Comparison between Volumetric Modulated Arc Therapy, Helical Tomotherapy and Conventional Electron and Photon Field Combination

Purpose: Homogeneous irradiation of the scalp is challenging due to relatively complex and superficial treatment volume. Conventional treatment approach of combining matched electron and photon fields produces dose heterogeneity, especially at matched lines. Fixed gantry IMRT techniques have not been able to provide clinically acceptable plans but helical tomotherapy has been demonstrated to be an alternative option. We have implemented total scalp treatment with volumetric modulated arc therapy (VMAT) and compared the dosimetric characteristics to tomotherapy and conventional method. Materials and Methods: Two patients have been planned for total scalp irradiation using RapidArc VMAT, helical tomotherapy and conventional electron and photon field combination. The same anatomy and structure sets have been used for the planning purposes. After each operator achieved clinically acceptable results for the particular method, the dose distributions and dose volume histograms were compared. Results: VMAT and tomotherapy provide significantly more homogeneous dose distribution and target coverage. Maximum PTV dose with VMAT and tomotherapy were 20% and 30% less than the conventional method respectively. Although, the conventional method provided 2/3 less dose to brain at D50% and D75%, tomotherapy and VMAT gave lower dose to the brain in high‐dose regions. Brainstem was best spared by conventional method with 1/4 of the maximum dose delivered with tomotherapy and VMAT. Tomotherapy provided more homogeneous dose distribution than VMAT but the brain and brainstem sparing were comparable. Conclusions: VMAT for total scalp irradiation is a clinically acceptable and comparable to tomotherapy. VMAT provides significantly more homogeneous distribution than conventional method. VMAT and Tomotherapy give lower dose to the brain in high‐dose regions than conventional method. Moreover, VMAT and tomotherapy plans can be delivered more reproducibly and reliably than conventional treatments. Average beam on time for VMAT and tomotherapy were 2.5 mins and 7.7 mins respectively. Research sponsored by Varian Medical Systems.

Dosimetric comparison of three different treatment techniques in extensive scalp lesion irradiation

Background and purpose This study compared lateral photon/electron plan (3DCRT), intensity modulated radiation therapy (IMRT) plan, and high dose rate (HDR) brachytherapy plan for total scalp irradiation. Materials and methods The techniques were planned on a patient with squamous cell carcinoma of the scalp for a prescribed dose of 60 Gy. Conformity indexes and dose volume histograms were used for the comparison. Results Clinical target volume coverage factors for 3DCRT, IMRT, and HDR were 0.976, 0.998, and 0.967, and Conformation Numbers were 0.532, 0.713, and 0.761, respectively. The dose gradient across the target was 59–136%, 91–129%, and 58–242% for 3DCRT, IMRT, and HDR techniques, respectively. The 3DCRT and IMRT techniques produced low optical structure doses. 3DCRT produced hotspots in the brain, while IMRT produced brain sparing. HDR produced the highest integral doses to the brain and optical structures. Conclusions IMRT provided the best target dose homogeneity and coverage, and delivered clinically acceptable doses to normal structures. HDR produced the most conformal plan, but the total dose delivered is limited by doses to the brain and eyes. HDR is a clinically feasible alternative for less extensive lesions, lower prescription doses, and for patients who cannot lie on the treatment table.

Dosimetric verification of helical tomotherapy for total scalp irradiation

Total scalp irradiation is a treatment technique used for a variety of superficial malignancies. Helical tomotherapy is an effective technique used for total scalp irradiation. Recent published work has shown the TomoTherapy planning system to overestimate the superficial dose. In this study, the superficial doses for a helical tomotherapy total scalp irradiation have been measured on an anthropomorphic phantom using radiochromic and radiographic film as well as a new skin dosimeter, the MOSkin. The superficial dose was found to be accurately calculated by the Tomo-Therapy planning system. This is in contrast to recent reports, probably due to a combination of the smaller dose grid resolution used in planning and this particular treatment primarily consisting of beamlets tangential to the scalp. The superficial dose was found to increase from 33.6 to 41.2 Gy and 36.0 to 42.0 Gy over the first 2 mm depth in the phantom in selected regions of the PTV, measured with radiochromic film. The prescription dose was 40 Gy. The superficial dose was at the prescription dose or higher in some regions due to the bolus effect of the thermoplastic head mask and the head rest used to aid treatment setup. It is suggested that to achieve the prescription dose at the surface (< or =2 mm depth) bolus or a custom thermoplastic helmet is used.

Carotid atherosclerotic disease following childhood scalp irradiation

Objective During the first half of the 20th century, scalp irradiation was a standard treatment for children suffering from Tinea Capitis. These children are now more than 50 years old, reaching the age when manifestations of atherosclerosis are common. We investigated the possible association between childhood low dose scalp irradiation and development of carotid atherosclerosis in adulthood. Methods The study included 145 individuals treated by irradiation in their childhood, and 150 matched control subjects with no history of irradiation. The occurrence of stroke was disregarded during the inclusion. B-mode ultrasound imaging and US Doppler were used to measure carotid, femoral (distant from the radiated area) and intima media thickness (IMT). Blood lipids and homocysteine were also evaluated. Results No significant differences in the baseline patients’ characteristics were observed. There were no differences in incidence of femoral IMT or prevalence of femoral stenosis between the groups. However, in the carotid of the irradiated group, a significantly elevated IMT and significantly increased prevalence of carotid stenosis were observed ( p < 0.001). In the irradiated group, 30.3% and 39.3% had stenosis in the right or left carotid arteries, compared to 12.7% and 16% in controls( p < 0.001), adjusted OR = 5.36[CI:2.78–10.33] . More participants in the irradiated group had experienced ischemic stroke: 13 patients (9%) from the irradiated group vs. 3 patients(2%) from the non-exposed group, p = 0.01. Conclusions Childhood scalp irradiation is a significant and thus far underestimated risk factor for adult carotid atherosclerosis disease. Physicians should be aware of the existence of such high risk populations.

Extensive Scalp Irradiation Technique using Modulated Electron Radiotherapy Delivered by Photon Multileaf Collimator

Extensive Scalp Irradiation Technique using Modulated Electron Radiotherapy Delivered by Photon Multileaf Collimator

SU‐FF‐T‐173: Dosimetric Comparison of Three Different Treatment Techniques for Extensive Scalp Lesion Irradiation

Purpose: Homogeneous scalp irradiation poses technical and dosimetric challenges due to the complex shape of the target. The purpose of this study is to compare conventional electron/photon therapy, photon IMRT, and HDR brachytherapy for treatment of extensive scalp lesions. Method and Materials: A 73‐year‐old man presented with extensive squamous cell carcinoma of the scalp. A custom helmet‐shaped mold was made and the target area delineated. The following three treatment methods were evaluated: a 3D plan using lateral photon/electron fields with moving junctions, an IMRT plan using seven coplanar beams, and a brachytherapy plan with catheters placed on the outer side of the mold. All plans were created for the same biological effective doses of 60 Gy. TLDs were used to verify the accuracy of the analyzed techniques. Coverage factors, dose conformity indexes, global conformity indexes, minimum, maximum and mean doses were presented for the scalp and critical structures including the brain and eyes. Results: Dosimetry parameters were normalized to 95% of prescription dose. Clinical target volume coverage factors in electron/photon, IMRT and HDR techniques were 0.976, 0.998, 0.957, and target conformity indexes were 1.98, 1.67, and 1.38, respectively. The dose gradient across the target was 59–136%, 91–129%, and 58–242% for electron/photon, IMRT, and HDR techniques, respectively. The lowest maximum dose to the eyes was achieved with external beam techniques. HDR produced the lowest maximum dose to brain, while IMRT irradiated the least amount of brain above 45 Gy. The measurements agreed within 5% of the calculated doses. Conclusion: IMRT provided better dose homogeneity and target coverage, and delivered lower doses to normal structures than the other techniques. While dose inhomogeneity in the target region was higher in HDR, this technique produced the most conformal plan. Therefore, our department selected IMRT and HDR for extensive scalp lesion treatment.

SU-FF-T-25: A Modified Azakawa Technique for Total Scalp and Neck Irradiation Utilizing a Custom Wax Bolus

Purpose: To develop a durable custom bolus helmet for Total Scalp and Neck Irradiation and to quantify the dosimetric aspects using a Modified Azakawa Technique for treatment delivery. Method and Materials: A custom bolus helmet for total scalp and neck treatment was fabricated from dental wax overlaid on a dual exoskeleton of Med Tech™ face mask mesh that conformed to the patients head. With helmet on, the patient was immobilized with a conventional facemask. Following CT simulation, treatment planning was performed in ADAC™ Pinnacle 3 planning system in heterogeneous mode for the combined photon and electron treatment fields. Opposed photons fields (6x) treat the sagital scalp and posterior neck; lateral scalps are treated with en face electrons that overlap the photon fields by 3–4 mm. Lateral necks were treated with en face electron fields that abutted the electron scalp fields. Beam central axes were kept coincident to provide ease of setup for the 6 customized ports. After half of the dose was delivered all field junctions were “feathered” by altering the junction locations by about 1 cm. A diode with 2mm build‐up was calibrated as a point detector to validate the dosimetry at multiple patient points. Results: Compared to the maximum dose of the prescription, the measured doses typically ranged from −5% to +15%; a single point yielded +20% at a photon and electron junction. Conclusion: The wax helmet proved to be extremely durable for more than 30 fractions. Additionally, the helmet provided “instant bolus” easily accommodated by the patient, appreciated by the RTT staff, and aided in reproducible dosimetry for this challenging treatment site.

225 Total scalp irradiation using intensity modulated radiotherapy for scalp lymphoma

225 Total scalp irradiation using intensity modulated radiotherapy for scalp lymphoma

Total scalp irradiation using helical tomotherapy

Homogeneous irradiation of the scalp poses technical and dosimetric challenges due to the extensive, superficial, curved treatment volume. Conventional treatments on a linear accelerator use multiple matched electron fields or a combination of electron and photon fields. Problems with these techniques include dose heterogeneity in the target due to varying source-to-skin distance (SSD) and angle of beam incidence, significant dose to the brain, and the potential for overdose or underdose at match lines between the fields. Linac-based intensity-modulated radiation therapy (IMRT) plans have similar problems. This work presents treatment plans for total scalp irradiation on a helical tomotherapy machine. Helical tomotherapy is well-suited for scalp irradiation because it has the ability to deliver beamlets that are tangential to the scalp at all points. Helical tomotherapy also avoids problems associated with field matching and use of more than one modality. Tomotherapy treatment plans were generated and are compared to plans for treatment of the same patient on a linac. The resulting tomotherapy plans show more homogeneous target dose and improved critical structure dose when compared to state-of-the-art linac techniques. Target equivalent uniform dose (EUD) for the best tomotherapy plan was slightly higher than for the linac plan, while the volume of brain tissue receiving over 30 Gy was reduced by two thirds. Furthermore, the tomotherapy plan can be more reliably delivered than linac treatments, because the patient is aligned prior to each treatment based on megavoltage computed tomography (MVCT).

Radio-induced malignancies of the scalp about 98 patients with 150 lesions and literature review

- The induction of malignant diseases is one of the most concerning late effects of ionizing radiation. The topic of this study deals with skin tumors developed in the irradiated areas in children given X-ray therapy for tinea capitis. - All patients with malignant tumors of the scalp referred to Salah Azaiz Institute between 1970 and 2001 have been questioned in order to determine if there had been a prior X-ray irradiation for tinea capitis, its modality, and its consequences. The first scalp irradiation goes back to 1922 and the last was performed in 1963. - Ninety-eight patients with 150 radio-induced cancers of the scalp following irradiation for tinea capitis are reported (1.5 lesion per patient). The patients were irradiated in various hospitals and dispensaries throughout the country. Eighty-one patients (82%) had only one session of radiation. The average age at irradiation was 12 (+/-6) years, the latent period for radiation-induced skin cancers was 36 (+/-14) years. In 61 patients (62%), the scalp appeared normal and in 38% radiodermatitis was noted. Patient age at diagnosis of malignancy varied from 20 to 83 years with an average of 47 years. Basal cell carcinomas (125 cases) and spinocellular carcinomas (16 cases) were the most common, three other cases of annexial tumors, two malignant non-Hodgkin's lymphomas and four melanoma lesions are also present. Radiotherapy was used for the treatment of 74 patients (alone in 42 and associated with surgery in 32 patients); 14 patients had exclusive surgical excision. - Basal cell carcinomas are the most frequent tumors arising on chronic radiodermatitis. In spite of the long latency period, patients' young age at irradiation explained the occurrence of these cancers at a relatively young age. Literature review is suggesting recessive mutation of tumor-suppressor genes as the characteristic abnormality in radio-induced cancer.

Thyroid Cancer Following Scalp Irradiation: A Reanalysis Accounting for Uncertainty in Dosimetry

In the 1940s and 1950s, over 20,000 children in Israel were treated for tinea capitis (scalp ringworm) by irradiation to induce epilation. Follow-up studies showed that the radiation exposure was associated with the development of malignant thyroid neoplasms. Despite this clear evidence of an effect, the magnitude of the dose-response relationship is much less clear because of probable errors in individual estimates of dose to the thyroid gland. Such errors have the potential to bias dose-response estimation, a potential that was not widely appreciated at the time of the original analyses. We revisit this issue, describing in detail how errors in dosimetry might occur, and we develop a new dose-response model that takes the uncertainties of the dosimetry into account. Our model for the uncertainty in dosimetry is a complex and new variant of the classical multiplicative Berkson error model, having components of classical multiplicative measurement error as well as missing data. Analysis of the tinea capitis data suggests that measurement error in the dosimetry has only a negligible effect on dose-response estimation and inference as well as on the modifying effect of age at exposure.

Intractable partial epilepsy following low‐dose scalp irradiation in infancy

We report the development of intractable epilepsy in 3 patients treated with irradiation to "strawberry" scalp nevi in infancy. Low-dose radiation was used (12 and 13 Gy in 2 of the patients). The clinical evolution suggested a recognizable and distinctive postradiation syndrome. There was concordance between the site of radiation as shown by localized alopecia, the clinical features of the partial seizures, and electrographic abnormalities. The clinical picture was unlike delayed cerebral radiation necrosis of adulthood, which is not thought to occur at doses below 50 Gy, in 2-Gy fractions. Neurological deficits were not progressive and in 2 patients there was no evidence of parenchymal injury on cranial magnetic resonance imaging scanning. These differences suggest pathogenetic differences to cerebral radiation injury of adulthood, probably relating to the interaction between nervous system development, individual susceptibility, and the low doses of radiation employed.

Treatment of cutaneous angiosarcomas of the head and neck.

A total of six patients with cutaneous angiosarcomas involving the head and neck were treated during the period 1985-1994. The distribution of sites between the scalp and the rest of the head and neck was equal. Initial local treatment involved surgery for four patients and radiotherapy for two patients. In the surgical group, following seemingly adequate macroscopic surgical excision, all four patients had inadequate surgical margins on histology. Five of six patients had disease recurrence within the head and neck and of these a further three went on to have a second episode of recurrence. Median time to recurrence was 8 months. All cases were misdiagnosed clinically at initial presentation and three of six had initial inconclusive histology. Cutaneous angiosarcomas of the head and neck is an aggressive multicentric cancer. Radiotherapy offers the only real chance of obtaining adequate local control even if surgical excision is carried out. Radiotherapy must encompass wide fields and whole scalp irradiation is mandatory for scalp lesions. A combination of laterally opposed photon and electron fields provides a simple, quick and effective means to deliver a tumoricidal dose of 50 Gy to the whole scalp with minimal irradiation of the underlying brain.

Dosimetric evaluation of total scalp irradiation using a lateral electron-photon technique

Purpose : To evaluate the radiation dosimetry of a new technique for total scalp irradiation. Methods and Materials : A treatment technique described by Akazawa (1989) has been studied. During each fraction, two electron and two photon fields are treated. While most of the lateral scalp is treated with the electron fields, a rind of scalp close to the midsagittal plane is irradiated by parallel-opposed lateral photon fields. A wax bolus is used to build up skin dose and to protect the brain from electron dose. The dose distribution and dose-volume histograms were evaluated for different field arrangements using a 3-dimensional treatment planning system. After modifying the technique, in-vivo thermoluminescent dosimetry were used to evaluate the dose distributions for the first two patients. Results : To compensate for the lack of dose from the opposed photon field at the junction, the technique was modified using overlapped fields instead of abutting fields. A field overlap of 3 to 4 mm between the electron and photon fields was found optimal. When used with the field junction shift of 1 cm midway through the treatment, this scheme resulted in a dose uniformity of -5% to +15% of the prescrived dose in the region of abutment. Results of the 3-dimensional dose calculation were supported by in-vivo thermoluminescent dosimetry on two patients. Conclusion : On the basis of computer dose calculations and in-vivo dosimetry, Akazawa's technique for scalp irradiation can be improved by using a 3 to 4 mm overlap of electron and photon fields. This modified technique is practical and produces clinically acceptable dosimetry.

Factors Affecting the Development of Skin Cancer after Scalp Irradiation

A nested case control study of persons who developed skin cancer after scalp irradiation in childhood revealed two risk factors for the appearance of radiation-induced skin cancer: (a) an apparently higher radiation dose delivered inadvertently, manifested by a higher prevalence of alopecia and radiation dermatitis (RR = 3.4; CI 1.3-8.8); (b) a more frequent exposure to the sun, manifested by summer sunbathing (RR = 2.6; CI 1.1-6.1). These findings may have certain implications with regard to the understanding of radiation-induced cancer, after low-dose radiation exposure, in general.

INCREASED RISK OF BREAST CANCER AFTER LOW-DOSE IRRADIATION

A significant increase in the risk of breast cancer has been found for the most recent 5-year period of a long-term follow-up study of children subjected to scalp irradiation, in whom a carcinogenic effect was previously only apparent in the head and neck. This increased risk was found among women aged 5 to 9 years at exposure. The breast had been exposed to a low radiation dose of approximately 16 mGy.

Thyroid cancer following scalp irradiation.

A sixfole increase in the risk of thyroid cancer was observed among 10,902 persons irradiated for scalp tinea in childhood as compared to two matched control groups. The dosimetry studies demonstrated that the original mean dose given to the thyroid was less than 9 rads, yielding a risk of 6.3/10(6)/year. This carcinogenic effect of low-level radiation must be considered in the planning of safety measures against potential public health hazards.