There are an estimated 17 million new cases of cancer globally each year. The top four cancers occurring worldwide are lung, breast, bowel, and prostate cancer, respectively. In men, prostate cancer is the most common form of non-skin cancer.

There are a variety of treatment options available when treating prostate cancer, and surgery and radiotherapy are the main treatment options presented to patients. These techniques are, however, associated with sexual, urinary, and bowel-related side effects.

One of the standard treatments for localised prostate cancer is conventional radiation therapy. However, conventional radiation therapy brings considerable acute and late adverse effects to the gastrointestinal (GI) and genitourinary (GU) tract. These side effects continue to be a major concern for both patients and physicians. For instance, in a study conducted by Fiorino et al., the risk of experiencing ≥grade 2 GI and GU side effects is about 5%–20% when undergoing conventional radiotherapy. 

With the materialisation of modern conventional radiotherapy techniques, the risk of toxicity on organs at risk, namely the bladder, rectum, and seminal vesicle, have decreased to 5%–10%. The use of proton beams in radiation therapy further reduces this risk with its characteristic Bragg peak, whereby protons can be controlled to stop directly within the tumour, analogous to its energy.

In order to improve life expectancy and overall quality of life, the Japanese government have applied efforts into funding advanced research for the treatment of cancer, with one such effort being proton beam therapy.

Currently there are 14 proton beam facilities within Japan, and as of April 2018, proton beam therapy for prostate cancer is included in Japanese public insurance coverage, thereby removing the financial burden for patients who will undergo this procedure. The number of patients being treated for localised prostate cancer with proton therapy in Japan continues to increase in popularity, due to its promise as a superior treatment for localised prostate cancer.

In a January 2019 literary review of proton therapy for localised prostate cancer in Japan by Japanese researchers in the Journal of Clinical Medicine, proton therapy for prostate cancer was highlighted as superior to other forms of conventional radiotherapy across multiple studies. The incidence of acute and late toxicities concerning the GI and GU tract, as well as radiation doses to organs of risk such as the bladder, bowel and seminal vesicles, were shown to be significantly lower compared to conventional radiotherapy treatments. Proton therapy has also shown its benefits in patients’ prognosis and quality of life. Biochemical control of patients who completed proton therapy are significantly favourable in prostate cancer patients, including high and very high risk cases. The researchers concluded that proton beam therapy is an effective and suitable treatment option for localised prostate cancer.

To find out if proton therapy is appropriate for you or a loved one, please do not hesitate to contact us.

Resources used:

Cancer Research UK. World Cancer Statistics. Available online (accessed on 12 June 2020).

Fiorino, C.; Sanguineti, G.; Cozzarini, C.; Fellin, G.; Foppiano, F.; Menegotti, L.; Piazzolla, A.; Vavassori, V.; Valdagni, R. Rectal dose-volume constraints in high-dose radiotherapy of localized prostate cancer. Int. J. Radiat. Oncol. Biol. Phys. 2003, 57, 953–962.

Hoshina, R.M.; Matsuura, T.; Umegaki, K.; Shimizu, S. A Literature Review of Proton Beam Therapy for Prostate Cancer in Japan. J. Clin. Med. 2019, 8, 48. 

Sakurai, H.; Ishikawa, H.; Okumura, T. Proton beam therapy in Japan: Current and future status. Jpn. J. Clin. Oncol. 2016, 46, 885–892. 

Takagi, M.; Demizu, Y.; Terashima, K.; Fujii, O.; Jin, D.; Niwa, Y.; Daimon, T.; Murakami, M.; Fuwa, N.;
Okimoto, T. Long-term outcomes in patients treated with proton therapy for localized prostate cancer. Cancer Med. 2017, 6, 2234–2243.

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.

Sources:

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.