Haematology: Involved-site radiotherapy concept
Free question published 29 August 2026
You are planning consolidation radiotherapy for a patient with localised nodal lymphoma. Which best describes the involved-site radiotherapy (ISRT) target volume concept?
- AIt electively irradiates whole nodal regions and adjacent uninvolved chains to cover microscopic spread
- BIt irradiates the entire lymphatic system above and below the diaphragm in a mantle and inverted-Y configuration
- CIt targets only the residual mass visible on post-chemotherapy imaging, ignoring the pre-treatment extent
- DIt abolishes any margin around gross disease because modern image guidance makes margins unnecessary
- EIt limits radiotherapy to a reduced volume based on the originally involved site, using modern imaging and 3D planning
Why E is correct
The ILROG guidelines state that extended-field and involved-field techniques targeting whole nodal regions have been replaced by limiting radiotherapy to smaller volumes based solely on detectable nodal involvement at presentation, defining the involved-site radiotherapy (ISRT) clinical target volume. ISRT integrates modern imaging and three-dimensional planning to reduce normal-tissue dose while maintaining local control.
And why the others are not
- AIncorrect: elective irradiation of whole regions and adjacent chains describes the older extended/involved-field approach that ISRT replaced.
- BIncorrect: mantle and inverted-Y fields are historical extended-field techniques, the opposite of ISRT.
- CIncorrect: ISRT is based on the pre-chemotherapy extent of disease (adjusted for anatomical changes), not solely the post-chemotherapy residuum.
- DIncorrect: ISRT still uses appropriate clinical and planning target margins; image guidance refines but does not abolish them.
Source ILROG - Modern radiation therapy for nodal non-Hodgkin lymphoma (involved-site RT) — Illidge T, Specht L, Yahalom J, et al. Modern radiation therapy for nodal non-Hodgkin lymphoma - target definition and dose guidelines from the International Lymphoma Radiation Oncology Group. Int J Radiat Oncol Biol Phys. 2014;89(1):49-58.
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