Radical treatment of angiosarcoma of the scalp using megavoltage electron beam therapy. By "Stephen M. Sagar, BSc, MRCP, FRCR and Chandrakant M.
1992, The British Journal of Radiology, 65, 421^24
Radical treatment of angiosarcoma of the scalp using megavoltage electron beam therapy By "Stephen M. Sagar, BSc, MRCP, FRCR and Chandrakant M. Pujara, PhD Newfoundland Cancer Clinic, Health Sciences Centre, St John's, Newfoundland, Canada
(Received 17 July 1991 and in revised form 25 October 1991, accepted 14 January 1992) Keywords: Angiosarcoma, Scalp, Megavoltage electrons
Abstract Angiosarcoma of the scalp is a multifocal neoplasm that is often initially managed by wide excision and surgical reconstruction. Invariably, adjuvant radiotherapy is required to improve local control. Primary radical radiotherapy to the scalp is not well documented. The major limitation is the technical problem of treating homogeneously an extensive superficial curved volume. We describe a practical technique that can be administered with a standard linear accelerator capable of high-energy electron production. The technique uses a multiple abutted fixed field set-up at constant source to surface distance and the patient is immobilized in a custom wax helmet which also serves to optimize the electron absorbed dose in the treatment volume. Surgical excision and reconstruction is reserved for the salvage of local relapse.
Angiosarcoma of the scalp is a rare malignancy predominantly affecting elderly men. It is a multifocal skin disease that may invade the skull, involve the face and metastasize to the cervical lymph nodes and the lung. Clinical presentation includes bruise-like lesions and dusky red-purple plaques. Histological study reveals malignant vascular channnels arising within the dermis, forming clusters that may straddle collagen bundles and usually leave the overlying epidermis intact. The origin of the malignant cells from either vascular or lymphatic endothelium is unclear. Prognosis is generally poor with 50% of patients dying within 15 months of presentation and only 12% surviving 5 years or more (Wilson Jones, 1976; Holden et al, 1987). Despite the overall poor prognosis, radical therapy to gain local control is essential in view of the distressing local progression of the lesions. Additionally, local control may contribute to survival, particularly if lesions are less than 10 cm in diameter (Holden et al, 1987). Previous reports of the efficacy of radiotherapy in the local control of disease have been disappointing. The literature includes reports of radioresistance (Morales et al, 1981), insufficient field margins (Knight et al, 1980) and complete local control but complicated by radionecrosis (Wilson Jones, 1976). Modern surgical management includes wide excision as determined by preoperative assessment of punch biopsies taken near the visible tumour margin (Barttelbort et al, 1989; Liu et al, 1990), but routine cervical lymphadenectomy (Hodgkinson et al, 1979) is controversial. Post-operative adjuvant radiotherapy to the reconstruction site and margin may reduce local recurrence (Hodgkinson et al, 1979; Barttelbort et al, 1989).
We considered that most reports of radiotherapy technique are insufficient, and case selection too biased towards more advanced cases, to conclude that primary radical radiotherapy is ineffective. On this basis, we managed the patient described in this report with carefully planned wide-field radiotherapy to the scalp using high-energy electrons and reserving wide surgical excision and reconstruction for local relapse. We aimed to deliver the most homogeneous dose possible to the target volume and to administer it with careful fractionation and a practical set-up technique to maintain patient immobilization and consistency of daily treatments.
""Current address and correspondence to: Dr S. M. Sagar, Cancer Treatment and Research Foundation of Nova Scotia, Halifax Cancer Centre, 5820, University Avenue, Halifax, Nova Scotia, B3H 1V7, Canada.
Method and materials
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Case report A 53-year-old man presented 3 months after suffering head trauma, complaining of persistent bruising of his scalp. He gave a past medical history of chronic irritation of his scalp associated with seborrhoeic dermatitis. Examination revealed three dusky, purple-red plaques on his scalp (Fig. 1). Site 1 was on the anterior vertex of the scalp and measured 2 cm x 3 cm. Site 2 was on the superior left temporoparietal region and measured 3 cm x 3 cm. Site 3 was immediately adjacent to site 2 in the left anterior temporal region and measured 4 cm x 5 cm. Site 1 was biopsied and demonstrated infiltration of the dermis by spindle and round cells that formed a network of anastomosing vessels. These vessels were lined by cells exhibiting nuclear enlargement and pleomorphism, consistent with angiosarcoma. Further investigation revealed no cervical adenopathy and no radiological evidence of invasion of the calvarium or metastasis to the lung. The patient's scalp was treated with a Varian Clinac 18 linear accelerator using multiple abutted 6 MeV electron beams at a source to surface distance (SSD) of 421
Stephen M. Sagar and Chandrakant M. Pujara
Figure 1. Angiosarcoma of the scalp presenting as three dusky, purple-red plaques on the scalp. Sites 1, 2 and 3 are described in the text.
100 cm, each directed through a common isocentre used as a reference point. The treatment volume extended from the tragus of the left ear over the left temporopar-
ietal scalp to 10 cm beyond the midline at the vertex to include much of the right temporoparietal scalp. Anteriorly, the volume extended from the supraorbital ridges to the occipitoparietal junction posteriorly. The tumour margin was a minimum of 4 cm anteriorly, 9 cm posteriorly and 9 cm on the right side, but only 3 cm could be achieved inferior to the left temporal lesion because of the insertion of the pinna and proximity of the left eye. The target volume depth was assessed from skull radiographs and defined as the distance from the surface of the scalp to 5 mm below the surface of the calvarium, a total depth of 7.5 mm. The scalp was shaved and the head positioned in the supine position. A 1 cm thick wax helmet was moulded over the patient's scalp to provide the necessary bolus, to position the patient and to enable set-up reference points to be marked. The margins of the volume were built up with thick wax to absorb the penumbra and scatter of the beams. The patients's shoulders and neck were supported by a custom cast of solidifying polyurethane foam (Voltafoam, Tiger Brand Products) and the wax helmet was slotted into the cast to provide rigid but comfortable immobilization (Fig. 2). The aim of the isodose plan was to deliver the most homogeneous dose possible to the curved volume in the coronal plane with rapid fall-off in dose at depth to avoid radiation-induced meningitis and cerebral atrophy. The angle between adjacent beams was optimized using a Theraplan L electron dose distribution planning system to reduce dose inhomogeneity between abutted fields to a minimum (Fig. 3). The optimum plan consisted of six beams of dimensions 8 cm x 19 cm set up sequentially at 30° intervals. A 25 cm x 25 cm cone with a 1 cm thick cerrobend cut-out insert was used to produce a field size of 8 cm x 19 cm at the surface of the wax helmet. The SSD was kept constant at 100 cm to the surface of the wax and standoff was 5 cm. Sequential beam entrance points 30° apart were marked on the wax mould. The position of the
Figure 2. The patient set up in the wax helmet inserted into a polyurethane foam cast on the couch top. The gantry is at 90° to the couch and the electron cone with collimator is attached. The collimator stands off 5 cm from the surface of the wax and the SSD is constant at 100 cm. Adjustment of the couch position is used to direct each sequential beam and points of incidence are marked on the wax shell.
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Angiosarcoma of the scalp: radical treatment with electron beam therapy
RIGHT
Wax Bolus E3 Scalp and Underlying Calvarium
Figure 3. Isodose distribution for a sixfield 6 MeV fixed electron beam technique. Thickness of the wax bolus is 1 cm except at the margin of the target volume, where it is 3 cm. Each beam is directed through a common reference point. The SSD is 100 cm; field size at the wax surface is 8 cm x 19 cm; and the angle between each beam is 30°. The weighting of each beam is 100% except beam number 1, which is 150%.
gantry was set horizontal at an angle of either 90° to of disease and no evidence radiologically of lung treat one side of the scalp or 270° to treat the contra- metastases. lateral side. The treatment table was rotated between each field by 30° and the SSD maintained constant by Discussion subsequent longitudinal and lateral adjustment of the Angiosarcoma of the scalp is a multifocal malignant treatment table. neoplasm requiring generous treatment margins to An additional matched anterior field was necessary to reduce the risk of local recurrence. Surgical excision treat the forehead and to enable a minimum anterior requires major reconstruction followed by adjuvant margin of 4 cm. radiotherapy and the cosmetic result may not be satisThe isodose distribution in the target volume was factory. The role of radiotherapy as a primary radical encompassed between 90% and 110% of the prescribed treatment of this rare tumour is poorly documented and dose. A single hot spot of 120% lay within the involved the optimal dose is unknown. The therapeutic gain of skin at site 3. The dose at the surface of the brain was a radiotherapy may be aided by the excellent vascular supply to the scalp. Furthermore, a good vascular maximum of 30% of the prescribed dose. The dose administered to the 100% isodose curve was supply allows reconstructive surgery to be reserved for a 50 Gy in 25 fractions over 5 weeks. Areas involved with salvage procedure. The therapeutic dilemma of initial angiosarcoma received a boost dose using a custom cut- management has been addressed by Morrison et al out of cerrobend to encompass tumour with a 1 cm (1990). Their patients received either surgery and adjumargin. The boost dose was administered with 6 MeV vant radiotherapy or radiotherapy alone. A six-to-eight electrons set up to the wax helmet and 10 Gy in 5 field technique that applied 6-9 MeV electrons was used. The whole scalp dose was 50 Gy at 2 Gy per fractions over 1 week was applied. fraction and involved regions were boosted to a median dose of 60 Gy. Despite most cases receiving radioResults Although the set-up procedure was practical and therapy with curative intent, the median freedom from reproducible, it was time-consuming, taking at least 45 relapse was only 7 months and survival 23 months. min. The patient developed erythema and dry desquaThe major limitation in the treatment of a large area mation of the scalp after 40 Gy but did not develop of scalp has been the physical problem of treating moist desquamation even in the boosted regions. homogeneously a superficial volume over a curved Assessment at 2 months following completion of radio- surface without a high exit dose through the cerebral therapy revealed complete resolution of disease apart cortex and without excess absorption into bone. from a persistent patch of purple discolouration in the Irradiation with high-energy electrons allows the treatleft temporal region. This was biopsied and histologi- ment of a superficial volume with a rapid fall-off in exit cally demonstrated a chronic inflammatory infiltrate but dose and avoids the relatively high bone absorption no evidence of angiosarcoma. After 10 months of displayed by orthovoltage photons. Multiple abutted follow-up, there was scanty regrowth of hair but no electron beams may result in dose inhomogeneities at clinical or histopathological evidence of local recurrence the field junctures. The achievement of a homogeneous Vol. 65, No. 773
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Stephen M. Sagar and Chandrakant M. Pujara
dose over a curved surface may be facilitated by the Acknowledgments We wish to thank the therapy technologists for their expert technique of arcing electrons, in which the electron collimator stands off the treatment surface and the facilitation of treatment, Dr David Jewer, specialist in recongantry rotates continuously through a defined angle and structive surgery, for joint management of this patient and the of Medical Illustration and Photography for the uses a computer-controlled dose delivery system Department figures. (Leavitt et al, 1985). Not all linear accelerators have the capability of administering dynamic arcing electrons. An alternative pseudoarc technique uses multiple fixed References fields and discards the electron collimator, resulting in ABLE, C. M., MILLS, M. D., MCNEESE, M. D. & HOGSTROM, K. R., 1991. Evaluation of a total scalp electron irradiation increased scatter and blending of adjacent fields (Boyer technique. International Journal of Radiation Oncology, et al, 1982). However, the resultant dosimetry to refine Biology, Physics, 21, 1063-1072. this techique is relatively complex. A further technique BARTTELBORT, S. W., STAHL, R. & ARIYAN, S., 1989. Cutaneous to reduce inhomogeneity at junctions of stationary fields angiosarcoma of the face and scalp. Plastic and uses a shift of the point of abutment after 50% of the Reconstructive Surgery, 84, 55-59. prescribed dose has been delivered (Able et al, 1991). BOYER, A. L., FULLERTON, G. D. & MIRA, J. G., 1982. An electron beam pseudoarc technique for irradiation of large The technique that we have described allows good areas of chest wall and other curved surfaces. International immobilization, ease of patient set-up and may be Journal of Radiation Oncology, Biology, Physics, 8, carried out on most linear accelerators with electron 1969-1974. capabilities. The "scalloped" dose distribution resulting HODGKINSON, D. J., SOULE, E. H. & WOODS, J. E., 1979. from the junctions of multiple abutted electron cones is Cutaneous angiosarcoma of the head and neck. Cancer, 44, reduced by using the minimum number of beams (in this 1106-1113. case, six fields) and optimizing the angle between the HOLDEN, C. A., SPITTLE, M. F. & WILSON JONES, E., 1987. beams (in this case, 30°). The wax scalp shell inserted Angiosarcoma of the face and scalp, prognosis and treatment. Cancer, 59, 1046-1057. into the polyurethane mould on the couch top immobilizes the patient, provides a surface to mark the succes- KNIGHT, T. E., ROBINSON, H. M. & SINA, B., 1980. Angiosarcoma (angioendothelioma) of the scalp. Archives of sive entry points of the electron cone, acts as bolus to Dermatology, 116, 683-686. treat to the appropriate depth and absorbs the superficial dose inhomogeneities produced at the site of abut- LEAVITT, D. D., PEACOCK, L. M., GIBBS, F. A. & STEWART, J. R., 1985. Electron arc therapy: physical measurement and ment of adjacent beams. Collimation of the electron treatment planning techniques. International Journal of beam by the cone at the entry point of the beam along Radiation Oncology, Biology, Physics, 11, 987-999. with thickening of the wax shell at the margins of the Liu, A. C , KAPP, D. S., EGBERT, B., WATERS, L. & ROSEN, J. treatment area results in a well defined target volume. M., 1990. Angiosarcoma of the face and scalp. Annals of Plastic Surgery, 24, 68-74. The optimum treatment of angiosarcoma of the scalp remains a dilemma. There is no good evidence that MORALES, P. H., LINDBERG, R. D. & BARKLEY, H. T., 1981. Soft tissue angiosarcomas. International Journal of Radiation surgical resection preceding radiotherapy increases the Oncology, Biology, Physics, 7, 1655-1659. local control or survival. It would be reasonable to W. H., PETERS, L. J., EVANS, H. L. & BYERS, R. M., reserve surgery for a salvage procedure. Having estab- MORRISON, 1990. Angiosarcoma of the scalp and face: a therapeutic lished a reproducible technique for the administration of dilemma (abstract). In Proceedings of the Seventy-Second electron beam therapy to the scalp, which was well Annual American Radium Society Meeting, Scottsdale (The tolerated by the patient, escalation of the applied dose American Radium Society, Philadelphia), p. 3. may be investigated to determine improvement in local WILSON JONES, E., 1976. Malignant vascular tumours. Clinical control. and Experimental Dermatology, 1, 287-312.
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