Fondazione Italiana Linfomi (FIL) expert consensus on the use of intensity-modulated and image-guided radiotherapy for Hodgkin's lymphoma involving the mediastinum.

Aim: Advances in therapy have resulted in improved cure rates and an increasing number of long-term Hodgkin's lymphoma (HL) survivors. However, radiotherapy (RT)-related late effects are still a significant issue, particularly for younger patients with mediastinal disease (secondary cancers, heart diseases). In many Centers, technological evolution has substantially changed RT planning and delivery. This consensus document aims to analyze the current knowledge of Intensity-Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT) for mediastinal HL and formulate practical recommendations based on scientific evidence and expert opinions.

Methods: A dedicated working group was set up within the Fondazione Italiana Linfomi (FIL) Radiotherapy Committee in May 2018. After a first meeting, the group adopted a dedicated platform to share retrieved articles and other material. Two group coordinators redacted a first document draft, that was further discussed and finalized in two subsequent meetings. Topics of interest were: 1) Published data comparing 3D-conformal radiotherapy (3D-CRT) and IMRT 2) dose objectives for the organs at risk 3) IGRT protocols and motion management.

Results: Data review showed that IMRT might allow for an essential reduction in the high-dose regions for all different thoracic OAR. As very few studies included specific dose constraints for lungs and breasts, the low-dose component for these OAR resulted slightly higher with IMRT vs. 3D-CRT, depending on the technique used. We propose a set of dose objectives for the heart, breasts, lungs, and thyroid. The use of IGRT is advised for margin reduction without specific indications, such as the use of breath-holding techniques. An individual approach, including comparative planning and considering different risk factors for late morbidity, is recommended for each patient.

Conclusions: As HL therapy continues to evolve, with an emphasis on treatment reduction, radiation oncologists should use at best all the available tools to minimize the dose to organs at risk and optimize treatment plans. This document provides indications on the use of IMRT/IGRT based on expert consensus, providing a basis for clinical implementation and future development.