Prostate cancer is the most common diagnosis treated at proton centres around the world. This is also the diagnosis where the largest number of patients were treated with protons (many tens of thousands). This is due to the relative regularity and small size of the irradiated volume and the stability of the tissues through which the proton beam must pass (muscle and skeleton). Despite being a diagnosis widely discussed in the professional community, it must be noted that there are currently no randomised trials comparing photon and proton radiotherapy for this diagnosis. The results of many thousands of treated patients clearly speak for proton radiotherapy.
1. According to the latest published data, the probability of cure measured as a 5-year relapse-free survival rate is 96.5% for low-risk prostate cancer, 93.7% for medium-risk prostate cancer with a favourable risk, and 91.2% for medium-risk prostate cancer with an unfavourable risk, and 75 to 85% for high-risk prostate cancer. Photon therapy and surgical procedures rarely see such results.
2. Proton radiotherapy has minimal toxicity (side effects). Recently published studies describe severe toxicity of treatment in less than 1% in a large population of patients. When compared with published data on photon radiotherapy and surgeries, such toxicity is minimal and significantly lower than that in other methods.
3. Compared with surgical therapy, proton therapy significantly reduces the risk of impotence, thus significantly increasing the patients’ quality of life.
4. In patients with high-risk prostate cancer, proton radiotherapy allows for irradiation of the pelvic lymph nodes, which have a high probability of subclinical involvement. This clinical situation best reflects the dosimetric and clinical benefits of proton radiotherapy as it causes no harm to organs in the abdominal cavity, in particular sigmoid colon.
5. Proton radiotherapy is a fully outpatient therapy and in most cases does not require sick leave. For low- and medium-risk prostate cancer, stereotactic radiation can be used that lasts 10 days.
According to current guidelines (international recommendations), both methods (photon and proton radiation) are considered usable. Proton radiotherapy is not a new method, the first exclusively clinical (not academic) centre was established in 1991 (Loma Linda, California, USA) and since then the number of patients treated with protons for prostate cancer has reached many tens of thousands. This is a technologically completely mature treatment proven in almost three decades of clinical use. Over the past two years, many publications have appeared that describe the benefits of protons for this specific diagnosis.
There are now excellent long-term results from large prospective studies and data showing the superior efficacy and safety of proton radiation compared to photon radiation (IMRT). The data come mainly from the USA and Japan, i.e., from countries where proton radiotherapy has the strongest supportive environment and is seen as a common procedure. In 2018, convincing data and published papers were reflected in the updated guidelines of the American Society for Therapeutic Radiology and Oncology (NCCN Guidelines v. 4 2018) where proton radiotherapy of prostate cancer is being considered a standard therapeutic method for prostate cancer.
In 2016, a major randomised study was published in the New England Journal of Medicine evaluating the effectiveness of treatment and the quality of life of prostate carcinoma patients treated surgically, by radiotherapy or initially only actively monitored. The study was conducted in 1,643 patients and the follow-up period was 10 years. The study demonstrated that:
