ESTRO 37 Abstract book

S194

ESTRO 37

MV TV LV RV

58 0.87 59 1.25 76 1.26 81 1.07

35 0.79 54 1.15 74 1.18 85 1.20

21 0.94 26 0.77 58 0.98 50 1.01

Purpose or Objective The understanding that mean heart dose is an important predictor for late cardiac morbidity >20 years after treatment for Hodgkin lymphoma (HL) is based on data from patients treated decades ago with standard large- field 2D radiotherapy (RT) techniques. Over time, RT treatment in HL has evolved with smaller radiation fields and more conformal techniques, such as 3DCRT, IMRT, and proton therapy. We investigated the relationship and correlation between mean heart dose and cardiac substructures with these more conformal techniques. Material and Methods Under IRB approval, we examined a pre-existing dosimetric database of involved-site radiotherapy (ISRT) plans for mediastinal lymphoma including 3D conformal (3D; n=26), intensity-modulated RT (IMRT; n=30), and proton therapy (PT; n=36). The database included heart and cardiac sub-structure contours, including the left anterior descending artery (LAD), mitral valve (MV), tricuspid valve (TV), aortic valve (AV), left and right ventricle (LV, RV), and left or right atria (LA, RA). For each plan, the mean heart dose was evaluated for correlation(R 2 ) and slope(beta) of the relationship with mean dose to the cardiac substructures. Results Mean heart dose for the cohorts was 18.5 Gy, 13.9 Gy, and 10.2Gy for 3D, IMRT, and PT, respectively. The linear regression plots between mean heart dose and the cardiac substructures are shown in Figure 1. Table 1 reports the correlation coefficient and slope for the relationships between mean heart dose and mean cardiac substructure dose, demonstrating less correlation with increasingly conformal delivery. A strong correlation(R 2 ≥70%) was observed for 3D with the RV, LV, and LAD and for IMRT with RV and LV; there was none for PT. A moderate correlation(50%

Conclusion Previously seen relationships between mean heart dose and mean substructure dose change with increasingly conformal techniques. This change in relationships indicate that contouring the cardiac substructures, especially the LAD and LV, is important in understanding the late cardiac risks of RT when using more conformal techniques, especially proton therapy. OC-0385 Patterns of Relapse and Outcomes of Orbital MALT Lymphomas treated with Radiotherapy J. Lee 1 , K.C. Keum 2 , C. Jaeho 2 , Y. Jin Sook 3 , C.O. Suh 2 1 Inha University Hospital, Radiation Oncology, Incheon, Korea Republic of 2 Yonsei university, Radiation Oncology, Seoul, Korea Republic of 3 Yonsei university, Ophthalmology, Seoul, Korea Republic of Purpose or Objective The purpose of this study is to report patterns of relapse and clinical outcome of primary orbital mucosa- associated lymphoid tissue (MALT) lymphomas patients treated with radiation therapy (RT). Material and Methods We reviewed 212 consecutive patients (246 treated eyes) who diagnosed orbital MALT lymphomas and received curative-intent RT between 1993 and 2013. The median age was 46 years. Tumor was involved in conjunctiva (134/246, 54%), eyelid (22/246, 9%), retrobulbar (79/246, 32%), and lacrimal gland (11/246, 5%). Median RT dose was 25.2 Gy in 14 fractions. Conjunctival and eyelid lesions were treated with 6-9 MeV electron, whereas retrobulbar and lacrimal gland lesions with photons. Lens shielding was applied for 71% of treated eyes. Results The median follow-up period was 5.3 years. Complete response was seen in 245 treated orbits (245/246, 99%). Relapse occurred in 29 patients with a median time of 39 months, that were consisted of local (11/212, 5%), contralateral orbit (18/212, 8%), and distant (7/212, 3%). RT was most commonly used as a salvage treatment after relapse (21/29, 72%). The 7-year local relapse, contralateral orbit relapse, and distant relapse rates were 5.8%, 4.6%, and 2.6%, respectively. There were 12 deaths with a median time of 144 months, one due to treatment related mortality with refractory MALT lymphoma and eleven due to intercurrent disease. The 7- year relapse-free survival, overall survival, cause-specific survival rates were 79.4%, 97.9%, and 98.8%, respectively. Regarding chronic toxicity, grade 3 cataracts were observed in 22 (9%) treated orbits with median time of 43 months, grade 3 nasolacrimal duct obstruction in 3 patients, and grade 2 dry eye in 16 patients. Conclusion Low-dose RT is an appropriate treatment for orbital MALT lymphoma in terms of high disease control and acceptable morbidity. Proper lens shielding provided the low incidence of cataract. OC-0386 Incidence of pneumonitis and CKD following novel FP IMRT TBI conditioning for full intensity HSCT. E. Durie 1 , E. Nicholson 2 , C. Anthias 2 , E. Dunne 1 , M. Potter 2 , M. Ethell 2 , C. Messiou 3 , J. Brennan 2 , S. Eagle 1 , W. Ingram 4 , F. Saran 1 , H. Mandeville 5 1 The Royal Marsden Hospital, Department of Radiotherapy, London, United Kingdom

Table 1. Correlation between mean heart dose and respective cardiac substructure 3DCRT IMRT PROTONS

Rho (R 2 ), %

Rho (R 2 ), %

BETA

Rho (R 2 ), %

BETA (Slope)

BETA (Slope)

Structure

(Slope)

AV LA RA

24 0.51 65 0.73 41 0.97 70 1.25

37 0.79 54 0.74 39 0.92 67 1.52

34 1.35 29 1.03 21 0.81 65 2.15

LAD