ESTRO 2020 Abstract book

S538 ESTRO 2020

experienced mild toxicities with grade 1 and 2 acute toxicity rates of 61% and 9%, respectively, with lower incidences of grade 1 (14% vs. 70%) and grade 2 (0% vs. 8%, P=.004) toxicities following low‐dose RT. Conclusion This long‐term analysis confirmed the excellent outcome of RT in the management of indolent primary skin lymphoma. The low‐dose RT concept with 4 Gy was associated with a comparable LCR and reduced rates of acute toxicity. However, the response rates were significantly lower for this group and low‐dose RT may therefore not be recommended as standard treatment. PO-0923 Total irradiation of the scalp and face in patients with cutaneous lymphomas G. Simontacchi 1 , A. Peruzzi 2 , G. Stocchi 2 , M. Mariotti 2 , B. Guerrieri 2 , V. Salvestrini 2 , C. Talamonti 3 , S. Pallotta 3 , L. Marrazzo 4 , I. Desideri 1 , S. Scoccianti 1 , L. Livi 2 1 AOU Careggi - U.O Radioterapia, DAI Oncologia, Firenze, Italy ; 2 University of Florence, U.O. Radioterapia, Firenze, Italy ; 3 University of Florence, U.O. Fisica Medica, Firenze, Italy ; 4 AOU Careggi, U.O. Fisica Medica, Firenze, Italy Purpose or Objective Aim of this study is to report on the use of total scalp and face irradiation in three patients affected by cutaneous lymphomas with an extensive involvement of the skin of scalp and face. Material and Methods We analyzed the treatment plans and the clinical outcome of three patients with cutaneous lymphoma, 2 Mycosis Fungoides (MF) and 1 Follicular Lymphoma (FL). Patients underwent a CT scan using a thermoplastic head‐shoulder mask. The clinical target volume (CTV) included the patient's entire skin surface of scalp and face (in the patient affected by Follicular Lymphoma both ears were not included in the CTV since were not involved by disease). The planning target volume (PTV) was obtained with an isotropic 3 mm expansion of the CTV. The prescription dose was 14 Gy for the two MF patients and 20 Gy for the FL patient in 2Gy fractions. They were treated with Helical TomoTherapy with daily IGRT with MVCT. A 2.5cm field width was used. An effective and robust template was generated for plan standardization. Ring structures around the PTV were contoured and used to improve gradient and conformity. Results Dosimetric parameters are reported in table 1. Despite the complex shape and superficial nature of the target, we obtained a good target coverage with the volume of PTV that received the 95% of the prescribed dose that ranged between 94,9% and 97,1%, with Dmax between 111,7‐ 112,2%. The dose to the organs at risk resulted within the dose constraints except for the lens (average dose range 10,2‐19,7Gy) and we obtained excellent dose gradient with low brain and hippocampal dose (average dose to hippocampus between 1,23 and 2,53Gy; dose to 40% of hippocampus between 1,09 and 2,65Gy, see Table 1). All three patients completed the treatment with excellent tolerance, the main acute side effects were grade 1 dysgeusia and grade 1 erythema. Two patients were partially bald before the treatment. All patients experienced complete acute alopecia (G2): one patient completely recovered his hair about 6 months after the treatment, two patients were partially bold before the treatment. No other late side effects have been recorded so far. The first MF patient had an almost complete response and has stable disease 15 months after the treatment. The second MF patient is in PR 6 months after the treatment. The FL patient had a partial response and will undergo a new biopsy.

cells and adoptive immunotherapy with conventional T cells and thymic‐derived CD4+/CD25+ FoxP3 regulatory T cells (Tregs). Our aim was to separate the Graft versus Leukemia (GvL) effect from Graft versus Host Disease (GvHD) and thus reduce the incidence of post‐transplant relapse. Material and Methods From January 2017 to December 2018, 11 children with ALL (8 male, 3 female, median age 9 years, range 5‐19, 6 in 1st complete remission (CR), 2 in 2nd and 3 in 3rd) underwent haploidentical HSCT. TBI total dose was 13.5 Gy delivered in 9 fractions twice a day (lung dose was 9 Gy) from days – 15 to –11 in 9 patients. In 3 children who required general anesthesia the TBI dose was 9.9 Gy (lung dose 6 Gy) delivered in 3 daily fractions from days –12 to ‐ 10. Chemotherapy included thiotepa 5 mg/kg on days ‐10 and ‐9; fludarabine 50 mg/m2 from days ‐10 to ‐6; cyclophosphamide 15 mg/kg on days ‐8 and ‐7. Haploidentical grafts consisted of 2 x106/kg Tregs, 1x106/kg Tcons and 10x106/kg purified CD34+cells. On day ‐2 Rituximab 200 mg/mq was administered as PTLD prophylaxis. No post‐transplant immunosuppression was given. Results TBI‐related acute toxicity was G1 in 11 patients. All patients achieved sustained full donor engraftment. Immune reconstitution was good, with peripheral blood T cells rapidly increasing. Grade II‐IV acute GvHD developed in 2 patients (18%) and chronic GvHD in none. 2 patients died (18%), 1 of invasive aspergillosis, 1 of grade IV aGVHD). Another patient relapsed and died after a second transplant. At a median follow up of 24 months (range 1‐ 28), 8 (73%) patients are alive in remission without cGVHD. Conclusion This transplant strategy was successful in haploidentical transplantation for children with high‐risk ALL. The conditioning regimen was associated with low toxicity and relapse rates. The appropriate Tcon/Treg ratio was confirmed to exert a powerful T‐cell dependent GvL effect with a low incidence of aGvHD. PO-0922 De-escalated radiotherapy for indolent primary cutaneous B-cell lymphoma M. OerteL 1 , K. Elsayad 1 , C. Weishaupt 2 , K. Steinbrink 2 , H.T. Eich 1 1 University Hospital Muenster, Department of Radiation Oncology, Muenster, Germany ; 2 University Hospital Muenster, Department of Dermatology, Muenster, Germany Purpose or Objective Radiotherapy (RT) has an established role in the curative treatment of indolent primary cutaneous B‐cell lymphoma. With the role of low‐dose regimens as 2*2 Gy being uncertain, we compared conventional‐dose RT to a low‐ dose approach and investigated outcome and toxicities. Material and Methods We retrospectively reviewed the medical records of 26 patients with 44 cutaneous lesions treated at our institution between 2007 and 2017, comprising 22 marginal zone lymphoma (PCMZL) lesions and 22 follicle center lymphoma (PCFCL) lesions. Seven lesions (16%) were treated with low‐dose RT (4 Gy) and 37 (84%) with conventional‐dose (≥24 Gy, median 40 Gy). Median follow‐ up duration was 76 months. Results The overall response rate (ORR) was 91% (complete response rate (CRR): 75%). The 5‐year local control rate (LCR) was 88% and the 10‐year LCR was 84%. The response rates were significantly higher following conventional‐RT dose (ORR: 92% vs. 86%; CRR: 84% vs. 29%, P=.007). In terms of radiation dose, the rate of infield relapses (14% vs. 11%, P=.4) and the 5‐year LCR (86% vs. 90%, P=.4) were comparable in the low‐dose RT and conventional‐dose group. During RT courses, about two‐thirds of patients