Proceedings of the 41st Annual ASTRO Meeting 403

160 MeV Protons in collaboration with Massachusetts General Hospital (MGH) and Massachusetts Eye and Ear Infirmary (MEEI). All patients were assessed prior to treatment by an ophthalmologist from MEEI and a radiation oncologist from MGH. All six suffered from the hereditary or bilateral form of disease. In all patients only one side was treated with radiotherapy, the other side being amenable either to other conservative treatment methods (N=3) or enucleation (N=3). Five were treated with a lateral proton field, one with an anterior oblique field. The median dose delivered to the treated eye was 42.6 Cobalt Gray Equivalent (CGE, 1 proton Gray = 1.1 CGE; range 42.6-49 CGE), delivered with protons only, at 2.13 CGE per fraction. Follow-up examination was performed at regular intervals. Serial facial photographs were available and an MRI at the time of last follow-up. On these studies the effects of proton irradiation on facial development were analyzed.

Results: Median age at treatment was 5.2 months (range 0930.3 months). At a median observation time of 9 years (range 6.6-l 1.6 years), all patients are alive and well. One never gained useful vision in the treated eye; the other eye had been enucleated. All other patients have good or excellent vision in the treated eye. Abnormalities of the bony orbit and the surrounding soft tissues were minimal on the treated side when compared to the non-enucleated untreated eye (N=3). The facial asymmetry was more pronounced on the enucleated side than the irradiated side in 2 patients, while the third patient had a normal appearance on both sides. Only two of the six patients had growth retardation recognized by their peers at school. The observed growth retardation was related to the amount of the bony orbit irradiated. No patient has shown radiation related abnormalities in teething. Serial facial photographs, correlated to SD-dosimetry, will demonstrate the excellent cosmetic results.

Conclusion: While providing the best currently available dose localization to the retina, proton irradiation minimizes the amount of non-target tissue receiving dose. This translates into the absence or near absence of adverse effects on the growth dynamics of several normal tissues: the interorbital area, the contralateral orbit and the maxilla. The follow-up is too short to assess benefits of this technique in reducing the incidence of radiation-induced neoplasms.

2244 CONFORMAL PROTON IRRADIATION OF THE POSTERIOR FOSSA: A COMPARISON STUDY WITH JD-PLANNED PHOTONS IN LIMITING DOSE TO AUDITORY STRUCTURES

Lin R, Hug EB. Schaefer RA, Miller DW, Slater JM, Slater JD

Loma Linda University Medical Center, Loma Linda, CA, USA

Purpose: Conventional radiation therapy in the treatment of posterior fossa tumors of the growing child can result in late toxicities such as sensorineural hearing loss, neuropsychological changes, and language and learning impairments. Advances in three dimensional treatment techniques have led to improved dose conformity to the posterior fossa. This report compares the normal tissue dose sparing capabilities of proton radiation therapy (PRT) with 3D conformal photon irradiation plans.

Methods and Materials: Nine pediatric patients underwent previously PRT for primary CNS malignancies (6 patients for posterior fossa tumors). Using the original planning CT-scans, posterior fossa, inner and middle ear as well as temporal lobes were delineated. Based on the same, in-house planning system and optimized by beam’s eye view mode, 3D treatment plans were generated for both, protons (4 fields) and photons (5 fields) to a prescribed dose of 54 Gy. Exposures of normal structures were calculated by averaging mean doses received and by dose-volume histogram (DVH) analysis.

Results: The posterior fossa was in all plans encompassed by the 95% isodose. All normal structures analyzed received considerable less radiation from PRT than from 3D photon plans. The cochlea received an average mean dose of 25 2 4% of the prescribed dose from PRT and 75 t 6% from photons - an average two thirds dose reduction. The middle ear was exposed to average mean doses of 10 t 6% (PRT) versus 54 i 4% (3D photons). DVH analysis confirmed dose reduction by use of PRT over the entire range of volume and dose. Average doses delivered to 90,50 and 10% of cochlea volume were 13, 26 and 37% for PRT compared to 61, 78 and 87% for 3D photons. Forty percent of temporal lobe volume was completely excluded from irradiation using protons. In contrast, by use of a 5-field photon technique to accomplish inner and middle ear sparing, 90% of temporal lobe received 31% of the prescribed dose. Doses to 50 and 10% temporal lobe volume were restricted to 2 and 67% (PRT) versus 56 and 100% (3D photons), respectively.

Conclusion: Due to its dose distribution characteristics, PRT resulted in increased sparing of sensitive auditory structures in immediate proximity to the posterior fossa, than 3D-conformal photon treatment plans. Posterior fossa conformity of 3D photons came at the expense of increasing amounts of normal tissue volume, represented by temporal lobes, r’eceiving low to moderate radiation dose levels. Minimizing doses to any normal tissue is of great importance, particular in treating children, given the radiation dose dependency of late toxicities.

2245 PROTON RADIATION THERAPY (PRT) FOR PEDIATRIC OPTIC PATHWAY GLIOMAS: COMPARISON WITH 3D PLANNED CONVENTIONAL PHOTONS AND A STANDARD1 PHOTON TECHNIQUE

Fuss M’, Hug EB’, Schaefer RA’, Nevinny-Stickel M’, Miller DW’, Slater JM*, Slater JD’

University of Heidelberg, Heidelberg, Germany’; Loma Linda University Medical Center, Loma Linda, CA, USA’

Purpose: Following adequate therapy, excellent long-term survival rates can be achieved for optic pathway gliomas. Therefore, avoidance of treatment related functional and cosmetic sequelae are of utmost importance. Optimized sparing of normal tissue (NT) has to be of major concern in the development of new treatment modalities. The present study compares proton radiation therapy (PRT) with a 3D planned multiport photon and a lateral beam photon technique for localized and extensive optic pathway tumors.

Materials and Methods: Between 2/1992 and 11/1997, seven children with optic pathway gliomas underwent PRT. Total doses of 50.4 to 54 CGE (Cobalt Gray Equivalent), administered in daily doses of 1.8 CGE were prescribed to the target volume. For this study, we computed 3D photon and lateral photon plans based on the same CT data sets and using the same treatment planning software for both, proton and photon planning. Radiation exposure for NT and discrete organs at risk was quantified based on dose volume histograms for all three plans.

404 1. J. Radiation Oncology l Biology l Physics Volume 45, Number 3 Supplement 1999

Results: GTV (gross tumor volume) ranged from 3.9 cm3 to 127.2 cm3. Conformity index (relation of encompassing isodose to GTV volume) was 2.3 for protons, 2.9 for 3D photons and 7.3 for lateral photons. NT encompassed at different isodose levels was calculated by subtracting GTV volume from the respective isodose volume. The relative increase in relation to NT encompassed by the 95% proton isodose volume was computed. Relative NT volumes for the 95% isodose volumes of proton, 3D photon and lateral photon plans were 1, 1.6 and 6. NT volume of proton plan isodoses at the 95%, 90%, 80%, 50% and 25% isodose level increased from 1 to 1.6, 2.8,6.4 to a maximum of 13.3. Relative volumes for 3D photons were 1.6, 2.4, 3.8, 11.5 and 34.8. Lateral plan relative values were 6, 8.3, 11.5, 19.2 and 26.8. Analysis for small (<20 cm3) and larger (>80 cm3) tumors showed that protons encompassed the smallest volumes of NT at all isodose levels. Comparable conformity and high dose gradient were achieved for proton and 3D photon plans in small tumors. However, with increasing tumor volume and complexity differences became larger. At the 50% isodose level, 3D photons were superior to lateral photons for small tumors, this advantage was equalized for larger tumors. At the lowest isodose level 3D photons encompassed the highest amount of NT. Analysis of organs at risk showed that PRT reduced doses to the contralateral optic nerve by 48% and 77% compared to 3D photons and lateral photons, respectively. Reductions were also seen for the chiasm (11% and 16%) and pituitary gland (13% and 16%), with differences at clinically relevant tolerance levels. Furthermore reduced dose exposure of both temporal lobes (sparing 39% and 54%) and frontal lobes was achieved with PRT.

Conclusion: PRT offered a high degree of dose conformity to target volumes and steep dose gradients, thus leading to substantial normal tissue sparing in high and low dose areas. It is expected that this will result in decreased long-term toxicity in the maturing child. For small tumors 3D photons were comparable in terms of dose conformity and high dose reduction to normal tissues, but inclusion of higher amounts of tissue at risk in mid and low dose areas may impair long-term results, Lateral photons resulted in inferior dose distribution with high radiation exposure of clinically relevant normal tissues, Data of this study can be applied to most low-grade childhood brain tumors, as the advantageous dose distribution of proton plans may offer reduced normal tissue complication probability whenever tumor control doses exceed normal tissue tolerance doses.

2246 CUTANEOUS AND SUBCUTANEOUS EWING’S SARCOMA-A RELATIVELY INDOLENT DISEASE

Chow E, Merchant TE, Pappo A, Jenkins J, Kun LE

St. Jude Children’s Research Hospital, Memphis, TN, USA

Purpose: The occurrence of extraosseous Ewing’s Sarcoma (ES) in deep soft tissues has been well described, cases in which this tumor occurs in a primary cutaneous or subcutaneous site have rarely been reported. The superficial variant may be less aggressive than are the more common bony and deep soft tissue counterparts with an apparently favourable outcome. A retrospective review of patients with cutaneous or subcutaneous ES was conducted to analyze the outcomes and patterns of failure.

Materials and Methods: Between July 1985 and March 1997, 14 patients with cutaneous or subcutaneous ES were treated at a tertiary hospital. The median age at presentation was 16 years (range 7-21 years). Presenting symptoms were a mass (lo), swelling (3) and soreness (1). Sites included trunk and pelvis (7), upper or lower extremity (4): and head and neck (3). The median size of the lesion was 3 cm (range, 1-13 cm).

13 had definitive surgical resections and I had biopsy of the mass at the time of referral. They were enrolled on an in-house ES protocol (ES-87 or ES-92) (n= 12) or on the POG-9354 protocol (n=2). All patients received chemotherapy, essentially composed of vincristine, doxorubicin, cyclophosphamide, ifosfamide, etoposide, and dactinomycin. Patients on ES-87 and ES-92 protocols received radiation (36 Gy) to the operative bed (150-180 cGy/fraction/day). Post-operative radiotherapy was omitted for 2 patients on POG-9354 who had complete resection of the primary tumors. Results: No patients had metastatic disease at presentation. Thirteen patients had gross total resection of the primary tumors prior to enrollment on chemotherapy. Surgical margins were negative (lo), microscopic (2), and indeterminate (1). Eleven were enrolled onto ES-87 and ES-92 protocols receiving radiotherapy to the tumour bed. Two with clear surgical margins were treated on POG-9354 receiving no radiation. The patient who had biopsy only received induction chemotherapy followed by definitive surgical resection and post-operative local radiotherapy.

The median follow-up was 77 months (range 17-111 months). None of the patients developed local recurrence or distant metastasis. Five patients developed treatment-related sequelae, including veno-occlusive disease of the lung and hemorrhagic cystitis (l), myelodysplastic syndrome (l), chemotherapy induced ovarian failure (l), moist desquamation (1) and dermato- fibroma within the radiotherapy portals (1).

Conclusions: Cutaneous and subcutaneous ES are associated with an indolent course and a favorable prognosis with multimodality treatment. The hypothesis that complete wide excision resulting in adequate local control without the use of post-operative radiation is being tested in the POG-9354 protocol to eliminate the potential risk of radiation-induced toxicity. Similarly, the low rate of metastatic disease and excellent overall outcome may suggest a role for less intensive chemotherapy, potentially limiting both acute and in particular, potential carcinogenic changes related to systemic therapies. The next goal is to tailor treatment to minimize toxitity while maintaining a high cure rate.

2247 MR-DETECTABLE NECROSIS IN EWING’S SARCOMAS IS ASSOCIATED WITH METASTATIC SPREAD AT DIAGNOSIS BUT HAS NO IMPACT ON OUTCOME IN PATIENTS WITHOUT METASTASES

Ahrens S’, Dunst J’, Ruebe C3, Paulussen M’, Juergens H’

University of Muenster, Dept. of Pediatric Oncology, Muenster, Germany’; Martin-Luther-Uiliversity Halle, Dept. of Radiotherapy, H&e, Germany’; University of Muenster, Dept. of Radiotherapy, Muenster, Germany3

Background: The presence and amount of visible necrosis has prognostic impact in several tumor types, e.g. squamous cell cancers of the head & neck and gliomas. We have evaluated whether radiologically identifiable necrosis has impact on the biological behaviour in Ewing’s sarcomas.

Materials & Methods: From 120993 through 311997, we have prospectively evaluated the pretreatment radiographic material in Ewing’s sarcoma patients with regard to a possible prognostic impact of necrosis. All patients were treated in the multicentric