Proton pencil beam scanning reduces secondary cancer risk in breast cancer patients with internal mammary chain involvement compared to photon radiotherapy

Abstract

Purpose Proton pencil beam scanning (PBS) represents an interesting option for the treatment of breast cancer (BC) patients with nodal involvement. Here we compare tangential 3D-CRT and VMAT to PBS proton therapy (PT) in terms of secondary cancer risk (SCR) for the lungs and for contralateral breast. Methods Five BC patients including supraclavicular (SVC) nodes in the target (Group 1) and five including SVC plus internal-mammary-nodes (IMNs, Group 2) were considered. The Group 1 patients were planned by PT versus tangential 3D-CRT in free-breathing (FB). The Group 2 patients were planned by PT versus VMAT considering both FB and deep-inspiration breath hold (DIBH) irradiation. The prescription dose to the target volume was 50 Gy (2 Gy/fraction). A constant RBE = 1.1 was assumed for PT. The SCR was evaluated with the excess absolute risk (EAR) formalism, considering also the age dependence. A cumulative EAR was finally computed. Results According to the linear, linear-exponential and linear-plateau dose response model, the cumulative EAR for Group 1 patients after PT was equal to 45 ± 10, 17 ± 3 and 15 ± 3, respectively. The corresponding relative increase for tangential 3D-CRT was equal to a factor 2.1 ± 0.5, 2.1 ± 0.4 and 2.3 ± 0.4. Group 2 patients showed a cumulative EAR after PT in FB equal to 65 ± 3, 21 ± 1 and 20 ± 1, according to the different models; the relative risk obtained with VMAT increased by a factor 3.5 ± 0.2, 5.2 ± 0.3 and 5.1 ± 0.3. Similar values emerge from DIBH plans. Contrary to photon radiotherapy, PT appears to be not sensitive to the age dependence due to the very low delivered dose. Conclusions PBS PT is associated to significant SCR reduction in BC patients compared to photon radiotherapy. The benefits are maximized for young patients with both SVC and IMNs involvement. When combined with the improved sparing of the heart, this might contribute to the establishment of effective patient-selection criteria for proton BC treatments.

Exploring Helium Ions’ Potential for Post-Mastectomy Left-Sided Breast Cancer Radiotherapy

“…Furthermore, while our facility was mainly designed for heavy ions, the proton beam focus width for low energy is known to be larger than cyclotron-based centers. However, despite this fact, and most probably linked to the use of a smaller range shifter (only 2 cm) compared to other facilities for shallow target treatments (between 5 and 7 cm), no compromise in the quality of our plan between target coverage and sparing of OAR was needed, and our dosimetric and NTCP predictions were similar to other published work [44][45][46][47][48], as shown in Tables 6 and 7. 4.2 (1.9-5.9) 1.1 (0.3-1.3)…”

Heart Sparing Radiotherapy Techniques in Breast Cancer: A Focus on Deep Inspiration Breath Hold

“… 104 Other studies have reported similar benefits when combining DIBH and IMPT in left-sided cancers requiring supraclavicular and IMC nodal irradiation. 107 , 108 Other factors should be taken into consideration when combining DIBH with protons. For example, a major advantage of combining DIBH with IMPT is that DIBH will minimize the dose variation from the interplay effect, which is defined as the difference between the absorbed dose volume during motion and when stationary.…”

Modelling the HPRT-gene mutation induction of particle beams: systematic in vitro data collection, analysis and microdosimetric kinetic model implementation

“…Growing interest has been registered in recent years toward radiotherapy-induced toxicity, including late effects such as secondary cancer induction. In this context, special attention is deserved for instance by paediatric, lymphoma and breast cancer patients treated with protons, according to the comparably good survival and long-life expectancy (Cella et al 2013, Abo-Madyan et al 2014, Cartechini et al 2020, Paganetti et al 2020. This is also relevant for particle beams heavier than protons, whose use is prospectively increasing.…”

“…Further developments of the present work are on-going and include the application of the RBE M ˜to the estimation of SCR after proton therapy plans. Specifically, for this aim, SCR models proposed in the past and recently tested also by our group can be expanded (Schneider and Walsh 2008, Schneider 2009, Cartechini et al 2020, taking into account at the same time the impact of a variable RBE for both cell survival and mutation induction. In the context of the current discussion on the clinical use of a variable RBE in proton therapy, this may contribute to shed light on the risks of side effects related to this technique and thus also to improve the patient selection procedure.…”

“…Cella et al 2013, Abo-Madyan et al 2014, Paganetti et al 2020, Cartechini et al 2020. This is also relevant for particle beams heavier than protons, whose use is prospectively increasing.…”