Proton beam Therapy (PBT) is increasingly used for the treatment of paediatric, central nervous system, skull base, and head and neck tumours. Today, there are over 75 particle therapy facilities in operation worldwide, with more in development. Whether proton therapy can play an important role as well in the treatment of anal and rectal cancer is under active investigation.
Anal and rectal cancers are surrounded by radio-sensitive organs, limiting the treatment options available to medical practitioners responsible for treating these forms of cancer. Proton radiotherapy has the potential to remove these limitations, and could be used to treat certain rectal and anal cancers with greater efficacy than conventional radiotherapy.
In a study published by medical researchers at the Harvard Medical School, the potential use of proton therapy was shown to reduce toxicities associated with treatment, increase patient compliance with treatment, minimise treatment interruptions and enables for the possibility of dose escalation (also known as hypofractionation).
The authors observe that currently, “… the maximal efficacy of radiation plans for primary and recurrent anorectal cancer is constrained by delivery techniques and modalities which must consider feasibility challenges and toxicity secondary to exposure of organs at risk.”
Given the minimal difference in biological effect between both protons and x-ray radiotherapy modalities, protons have drawn interest as a way of sparing adjacent organs at risk from unnecessary radiation, while delivering “tumoricidal” doses, and increasing the therapeutic effect of treatment.
Researchers are highly optimistic about proton therapy as an effective treatment for anal and rectal cancers (especially as intensity-modulated proton therapy and pencil-beam scanning techniques become more prevalent). Additionally, decreased doses to bone marrow and bowel may “improve tolerance of multi-modal treatment” and allow for dose escalation, in turn improving clinical and patient-reported outcomes.
In summary, proton therapy has the potential to more effectively treat anal and rectal cancers. Proton therapy can result in less short- and long-term side effects, and due to its precision, allows for dose escalation (hypofractionation), thereby increasing the chance of completely eliminating the disease.
To find out if proton therapy is appropriate for you or a loved one, please do not hesitate to contact us.
Colaco RJ, Nichols RC, Huh S, et al. Protons offer reduced bone marrow, small bowel, and urinary bladder exposure for patients receiving neoadjuvant radiotherapy for resectable rectal cancer. J Gastrointest Oncol 2014;5:3-8.
Raldow AC, Hong TS. Will There Be a Clinically Significant Role for Protons in Patients With Gastrointestinal Malignancies? Semin Radiat Oncol 2018;28:125-30.
Verma V, Lin SH, Simone CB, et al. Clinical outcomes and toxicities of proton radiotherapy for gastrointestinal neoplasms: A systematic review. J Gastrointest Oncol 2016;7:644-64.
Vaios EJ, Wo JY. Proton beam radiotherapy for anal and rectal cancers. J Gastrointest Oncol. 2020;11(1):176‐186. doi:10.21037/jgo.2019.04.03
Wolff HA, Wagner DM, Conradi LC, et al. Irradiation with protons for the individualized treatment of patients with locally advanced rectal cancer: A planning study with clinical implications. Radiother Oncol 2012;102:30-7.