Over the last 30 years, major advances have been made in the treatment
of lymphomas, here Hodgkin’s lymphoma. In 2018 we saw approximately 80000 new
cases worldwide, accounting for 0.4% of all new tumours [1]. In Sweden with a
10 million population, approximately 200 new cases are seen yearly. Even though
chemotherapy is very effective in Hodgkin’s lymphoma, radiotherapy plays a very
important role of the treatment. And as radiotherapy have evolved, so has the
treatment of Hodgkin’s lymphoma. 30 years ago, large mantle fields or inverted
Y were the standard and treated all lymphatic nodes cranial or caudal of the diaphragm.
Today, with the aid of better imaging, affected nodes can be pinpointed, the
resulting target volume kept smaller, and with advanced radiotherapy
techniques, irradiated volumes can be kept smaller as well. Can we enhance the
radiotherapy we deliver today?
Depending on stage, radiotherapy (RT) today will consist of treatment to
involved node (INRT) or involved site (ISRT). Doses usually lies between 20-30
Gy, more seldom 40 Gy. The volume is smaller today, but we still see some quite
large target volumes, as the RT will involve the initially engaged nodes.
The organs at risk (OAR) to consider are heart, lungs, thyroid, parotid
glands, esophagus, and mammary glands and if the target is within the lower
pelvis, kidneys, uterus, and the ovaries will have to be considered.
Today many patients are treated with different breath-hold techniques.
The advantages with breath-hold, would be both to have the target movement
under control and adding to the distance between the target and the OARs [2].
With rotational therapy the doses to OARs can be kept lower compared to 3D
conformal therapy (3DCRT). However, the rotational techniques add dose to the
whole circumference of the patient, and all possible OARs must be delineated to
be considered in the optimization. The possible advantages with protons could
be lower doses to organs at risk. But to consider protons it is important to
evaluate the patient breathing pattern, how much the target moves, and if
possible, use a breath-hold technique. The protons physical properties are what
we want to use to lessen the dose to OARs. However, it may interfere with the
breathing motion and add to the uncertainty using protons. This means that
unless breathing motion is very small, breath-hold techniques should be used to
ascertain target coverage and minimize motion. However, the size of the target
volume, specifically the depth of it, will affect the time it takes to deliver
the dose to the target, in turn setting the number of breaths the patient must
take for each beam.
Using protons for treating Hodgkin’s lymphoma is absolutely feasible but
may not be for every patient [3]. Target size, target localization as well as
the ability to comply with breath-hold techniques must be considered.
1.
Global, regional, and national burden of Hodgkin
lymphoma from 1990 to 2017: estimates from the 2017 Global Burden of Disease
study. Zhou L. et al. Journal of Hematology & Oncology (2019) 12:107 https://doi.org/10.1186/s13045-019-0799-1
2.
Comparative treatment planning study for mediastinal
Hodgkin’s lymphoma: impact on normal tissue dose using deep inspiration breath
hold proton and photon therapy, Edvardsson A. et al Acta Oncologica, (2019) 58:1, 95-104 https://doi.org/10.1080/0284186X.2018.1512153
3. Pencil beam scanning
proton therapy of Hodgkin’s lymphoma in deep inspiration breath-hold: A case
series report. Andersson K, Edvardsson
A, Hall A, Enmark M, Kristensen I. tipsRO (2020) 13, 6–10 https://doi.org/10.1016/j.tipsro.2019.11.006