Hematologic Malignancies

PV 01 - Poster Viewing Q&A - Session 1

SU_17_3094 - Defining Clinical Target Volume in Patients with Early Stage Indolent Lymphoma Treated with Definitive Radiotherapy

Sunday, September 15
1:15 PM - 2:30 PM
Location: ASTRO Innovation Hub

Defining Clinical Target Volume in Patients with Early Stage Indolent Lymphoma Treated with Definitive Radiotherapy
F. Al-Rowais1, D. A. S. Toesca2, M. S. Binkley3, R. Von Eyben2, and R. T. Hoppe4; 1Stanford University, Stanford, CA, 2Department of Radiation Oncology, Stanford Cancer Institute, Stanford University, Stanford, CA, 3Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, 4Stanford University School of Medicine, Stanford, CA

Purpose/Objective(s): Radiotherapy as a single modality can be used as curative treatment for stage I-II indolent lymphoma (nodular lymphocyte predominant Hodgkin's lymphoma {NLPHL} and follicular lymphoma). However, there is no consensus on the appropriate definition of involved site radiotherapy (ISRT) in this setting. The International Lymphoma Radiation Oncology Group (ILROG) and the National Comprehensive Cancer Network (NCCN) guidelines recommend that the “clinical target volume (CTV) should be more generous” than the easily identifiable gross tumor volume (GTV), however, the degree of that expansion is left to clinical judgment. In this retrospective review, we tried to define an appropriate CTV margin when using radiotherapy as single modality.

Materials/Methods: This is a retrospective review that included patients with early stage nodal follicular lymphoma and NLPHL, staged with PET CT and treated with definitive radiotherapy between 2003 and 2018. The distance between field edge on cranio-caudal dimension and GTV/surgical bed was assessed and correlated with patterns of relapse.

Results: A total of 40 patients were included (28 follicular lymphoma and 12 NLPHL). The median follow up was 74 months (3-196 months). We were unable to reproduce the treatment plans for 4 patients. The distance from GTV/surgical bed to the field edge superiorly was 2-17 cm (median 5 cm, mode 3 cm) and inferiorly was 2-22 cm (median 5 cm, mode 3 cm). Most common margin used was 3-6 cm. There were no isolated locoregional failures. Distant failure was identified in 9 patients, 3 of whom had locoregional failure as well.

Conclusion: A CTV margin of 3-6 cm in the cranio-caudal dimension when using radiotherapy as a single modality for treatment of early stage indolent lymphoma is associated with a low rate of locoregional failure and may be an acceptable GTV-CTV expansion when planning ISRT fields.
Margin cm Superior (#fields) Inferior (#fields)
1-2 4 4
3-4 13 16
5-6 13 13
7-8 2 3
9-10 3 3
11-12 3 1
13-14 2 0
17-18 1 0
21-22 0 1

Author Disclosure: F. Al-Rowais: Travel Expenses; Stanford University. D.A. Toesca: Travel Expenses; Stanford University. R.T. Hoppe: Travel Expenses; Stanford University. Chair; NCCN.

Fahad Al-Rowais, MD

Stanford University

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