The doctoral dissertation by Mikko Mankinen, from University of Jyväskylä (Finland), investigated how patient positioning and respiratory motion affect the dose delivery in modern breast cancer radiotherapy techniques.
Surgery and systemic therapy for breast cancer is often supplemented with radiotherapy to destroy any remaining cancer cells and reduce the chance of cancer recurrence. Traditionally, the treatment machine irradiates the breast using two radiation beams from two different angles. However, in volumetric modulated arc therapy, the treatment machine slowly rotates around the patient, irradiating the target from multiple angles with varying intensity. This allows the radiation dose to be shaped to the contours of the target tissue.
“Accurate shaping of the dose distribution is crucial, as radiotherapy may cause adverse effects such as pneumonitis, dermatitis or heart disease. However, increased conformality of the dose has been suspected to be more sensitive to patient motion and setup inaccuracies”, explains Mikko Mankinen from the University of Jyväskylä.
Simulation tools to assess treatment delivery
Mankinen’s dissertation presents high-precision computer simulations to evaluate how well the volumetric modulated arc therapy is delivered. The dissertation comprises three studies: the impact of respiratory motion on whole-breast irradiation, the effects of patient setup and anatomical changes during breath-hold treatments, and the differences in lung exposure to radiation between treatments delivered in free breathing and breath-hold.
“One of the major challenges in this field has been creating realistic simulations, especially when the patient and the treatment machine are in motion. Our models represent a clear improvement over previous approaches”, explains Mankinen.
Reproducibility and stability are highlighted
The simulations revealed minor changes in dose distribution to both the target and surrounding healthy organs in treatments delivered using both arc-based and conventional techniques. Despite these differences, the majority of the treatments met clinically acceptable accuracy levels.
“There is always some level of uncertainty in treatment delivery, so it was reassuring to see that the current safety margins were generally sufficient. However, even though our simulations were the most accurate to date, we could not include all sources of uncertainty, such as variations in patient posture stability. Based on our results, the quality of arc therapy may degrade more rapidly than that of conventional techniques. Special attention should be paid to minimizing the treatment uncertainties in arc therapy”, tells Mankinen.
Better attention to anatomy
The doctoral research expands the knowledge on selecting an appropriate irradiation technique during treatment planning, where the individual patient anatomy and treatment deliverability must be taken into account. Furthermore, the third article revealed that treatment delivery in breath-hold combined with careful treatment planning can reduce the irradiation of all healthy organs.
“The dissertation provides a comprehensive overview of the factors that influence the accuracy and safety of volumetric modulated arc therapy. The full potential of volumetric modulated arc therapy in sparing the healthy organs can be realized with thorough consideration of uncertainties and meticulous treatment planning”, concludes Mankinen.
Mikko Mankinen obtained his Master of Science degree in physics from the University of Jyväskylä in 2019. He conducted his doctoral research alongside the Finnish national medical physicist residency program. The research was supervised by adjunct professor Tuomas Koivumäki (Wellbeing Services County of Central Finland), adjunct professor Jan Seppälä (Wellbeing Services County of North Savo) and Senior Researcher Arttu Miettinen (University of Jyväskylä). The research was funded by the Finnish Ministry Social Affairs and Health and the Kalle, Vilho and Yrjö Väisälä foundation.
Mikko Mankinen defends his dissertation “Volumetric Modulated Arc Therapy for Breast Cancer – the Dosimetric Effects of Setup Uncertainty, Respiratory Motion and Deep-Inspiration Breath-Hold” on Thursday June 19, 2025, at 12.00 o’clock in the lecture hall FYS1 at the University of Jyväskylä. Acting as the opponent is Luca Cozzi, PhD, (Humanitas University) and as the Custos Associate is Senior Researcher Arttu Miettinen. The public defense is held in English.
The event will be streamed live online: https://m3.jyu.fi/jyumv/ohjelmat/science/vaitostilaisuudet/2025/suora-lahetys-vaitostilaisuus-mikko-mankinen
The research will also support the new Master of Science in Technology degree programme in Safety and Risk Management. The degree programme will start in 2026 and consist of bachelor’s, master’s and doctor of technology degrees.
The dissertation "Volumetric Modulated Arc Therapy for Breast Cancer – the Dosimetric Effects of Setup Uncertainty, Respiratory Motion and Deep-Inspiration Breath-Hold” will be available in the JYX publication archive: https://jyx.jyu.fi/jyx/Record/jyx_123456789_102997?sid=160206653