Proton Radiotherapy to Treat Oesophageal Cancer

August 17, 2023 — A 67-year old patient presenting with oesophageal cancer was treated at the Paul Scherrer Institute (PSI) with a form of radiation provided by protons, i.e. positively charged particles. This is the first time this type of radiotherapy has been used in Switzerland to treat an oesophageal tumour. The five-week course of treatment is part of a European clinical trial involving both PSI and University Hospital Zurich. Medical researchers are investigating whether proton therapy is suitable for treating this type of cancer, as it could potentially reduce lung complications that typically occur with traditional radiotherapy. 

“Today we have used proton radiotherapy to treat a patient with oesophageal cancer for the first time, within the framework of a collaborative European Phase III clinical trial,” confirms Damien Weber, senior clinician and Head of the Center for Proton Therapy (CPT) at PSI. “The 67-year-old patient has a Siewert type II tumour at the esophagogastric junction, which will be resected after our treatment.” Since 1996, PSI has been successfully treating patients with tumours in the head and neck area, as well as along the spine, but this technique has never been used before in Switzerland to treat oesophageal cancer. “We are delighted to now be able to offer this type of treatment to patients in Switzerland as part of a clinical trial,” says Matthias Guckenberger, Medical Director and Head of the Department of Radiation Oncology at University Hospital Zurich (USZ). 

USZ and PSI are building on their long-standing collaboration in cancer treatment to investigate whether protons offer advantages for radiotherapy of the oesophagus. This research is part of the pan-European PROTECT trial (PROton versus photon Therapy for Esophageal Cancer: a Trimodality Strategy), which compares the side-effects of conventional radiotherapy with proton therapy to treat oesophageal cancer. 

Rare type of cancer requires complex treatment 

Every year around 600 people in Switzerland, three quarters of them men, are diagnosed with cancer of the oesophagus. Although this makes it a relatively rare form of cancer, it is still the eighth most common cancer worldwide. 

In most cases the treatment involves a combination of chemotherapy and radiation, followed by surgery to remove any tumour residue and the surrounding lymph nodes. Since the excision of the tumour also requires the removal of a part of the oesophagus, the remaining healthy parts are subsequently connected with the stomach. 

Radiotherapy for oesophageal cancer can unfortunately lead to varying degrees of complications in the surrounding organs, especially the lungs. This sensitive organ sits right next to the oesophagus within the chest cavity and is often negatively affected by radiation directed at the tumour. Many patients, for example, subsequently develop pneumonia or other problems, which can complicate vital surgery or post-op recovery. 

Proton therapy could offer a solution. “Our hope is that proton radiotherapy should cause far fewer lung complications,” says Damien Weber. “We now want to verify whether our prediction is correct – for the good of all cancer patients.” 

Both protons and photons (used in traditional radiotherapy) can damage the DNA in tumour cells, killing them off. Although X-rays can be targeted at tumours with great precision nowadays, they also tend to affect the surrounding healthy tissue and may cause damage. Unlike photons, protons are electrically charged particles. Their depth of penetration into the tissue is precisely calibrated beforehand. Protons lose very little of their energy as they make their way to the site of the tumour, where they release their main effect. Potential damage to healthy tissue surrounding the tumour is therefore largely avoided. Medics hope this approach will lead to fewer lung complications after a course of radiotherapy. 

Pan-European study 

Nineteen research partners across Europe – including universities, hospitals and research centres – are joining forces in the collaborative PROTECT trial. “Because we work so closely together, we hope to be able to recruit several hundred participants, so the results of the study will carry far more weight,” says radiation oncologist Dominic Leiser, Head of Clinical Studies at PSI. Aarhus University in Denmark is the main project coordinator. PSI was one of the study initiators at European level. 

The project involves treating a total of almost 400 patients with non-metastatic oesophageal cancer, about 20 of them based in Switzerland. All study participants first undergo a course of combined radiotherapy and chemotherapy, followed by surgery to remove the tumour six to twelve weeks later. Around half of them will receive conventional photon X-rays at USZ, while the rest will be treated with protons at PSI. PROTECT is designed as a randomised trial in order to provide a direct comparison of the outcome of both types of treatment. At USZ all participants will not only receive conventional radiotherapy, but also chemotherapy followed by surgery to remove any tumour residue. 

“We are using all three modes of cancer therapy to ensure the best possible treatment outcome for this type of cancer,” explains Panagiotis Balermpas, principal investigator and Senior Physician at the Department for Radiation Oncology at USZ. “And irrespective of whether patients are given radiotherapy in the form of photons or protons, they will receive the very best treatment over the course of the study.” 

The PROTECT trial is always looking for new patients and screening their eligibility for participation in the study. The trial also includes patients with tumours at the gastro-oesophageal junction, where the oesophagus joins the stomach. 

“If our hope that proton radiotherapy can offer advantages in the treatment of oesophageal cancer can be confirmed, this type of tumour could be placed on the Ministry of Health’s indication list,” says Damien Weber. “This would mean that medical insurances would cover the cost of proton therapy for oesophageal cancer in future.” Matthias Guckenberger comments: “We have a great opportunity here to take the next step in the treatment of oesophageal cancer and improve existing therapy options.” 

For more information: https://www.psi.ch/en