PTC CLINIC
Information for Healthcare Professionals

In the Netherlands, they have a sophisticated indication system for proton radiotherapy. It is not based only on the parameters of a specific plan, but also on the absolute increase in risk for each individual patient. The baseline cardiovascular risk without radiotherapy is determined based on national statistics that take into account age, gender and the presence of cardiovascular risk factors. The risk from radiation exposure is modeled on the work of Darby et al., where for every Gray of the medium dose to the heart increases the risk by 7.4%. The limit is then determined by subtracting the individual risk from radiotherapy from the basic cardiovascular risk. If it is 2% and higher, a comparative proton plan is developed. The patient is sent for proton irradiation if the difference in risk between the proton and photon plan is 2% and higher.

We do not yet have such a precise recommendation in the Czech Republic. We believe that there are several groups of women who could benefit from proton radiotherapy.

Consideration of proton radiotherapy in patients with breast cancer:

• The first group are patients with left breast cancer in whom photon radiotherapy would lead to a high load on critical organs (heart Dmean > 2.5 Gy, left descending coronary artery Dmean > 10 Gy) and their life expectancy is longer than 15-20 years . They are most at risk after previous cardiotoxic treatment – chemotherapy, biological treatment (anthracyclines, trastuzumab).
• The second group are patients with pre-existing cardiac disease, in whom the same dose limits cannot be applied to the heart as in the healthy population.
• Another group consists of patients who are planned to have a larger volume of radiation, such as bilateral breast cancers or loco-regional radiation, including irradiation of the internal mammary nodes. As opposed to conventional radiotherapy, in this case proton radiotherapy does not have to choose a compromise between target volume coverage and reduction of critical organ toxicity.
• Patients who would benefit from proton radiotherapy are also those after previous radiotherapy in the chest, bilateral breast, or with inappropriate anatomical shape of the chest (pectus excavatum, heart pressing on the chest wall, etc.).
• The last group are patients with a diagnosed genetic syndrome that predisposes them to either a higher risk of tumor or increased toxicity (such as BRCA1 mutations).