Radiobiological and dosimetric impact of RayStation pencil beam and Monte Carlo algorithms on intensity‐modulated proton therapy breast cancer plans

Abstract

RayStation treatment planning system employs pencil beam (PB) and Monte Carlo (MC) algorithms for proton dose calculations. The purpose of this study is to evaluate the radiobiological and dosimetric impact of RayStation PB and MC algorithms on the intensity-modulated proton therapy (IMPT) breast plans. Methods: The current study included ten breast cancer patients, and each patient was treated with 1-2 proton beams to the whole breast/chestwall (CW) and regional lymph nodes in 28 fractions for a total dose of 50.4 Gy relative biological effectiveness (RBE). A total clinical target volume (CTV_Total) was generated by combining individual CTVs: AxI, AxII, AxIII, CW, IMN, and SCVN. All beams in the study were treated with a range shifter (7.5 cm water equivalent thickness). For each patient, three sets of plans were generated: (a) PB optimization followed by PB dose calculation (PB-PB), (b) PB optimization followed by MC dose calculation (PB-MC), and (c) MC optimization followed by MC dose calculation (MC-MC). For a given patient, each plan was robustly optimized on the CTVs with same parameters and objectives. Treatment plans were evaluated using dosimetric and radiobiological indices (equivalent uniform dose (EUD), tumor control probability (TCP), and normal tissue complication probability (NTCP)). Results: The results are averaged over ten breast cancer patients. In comparison to PB-PB plans, PB-MC plans showed a reduction in CTV target dose by 5.3% for D 99% and 4.1% for D 95% , as well as a reduction in TCP by 1.5-2.1%. Similarly, PB overestimated the EUD of target volumes by 1.8─3.2 Gy(RBE). In contrast, MC-MC plans achieved similar dosimetric and radiobiological (EUD and TCP) results as the ones in PB-PB plans. A selection of one dose calculation algorithm over another did not produce any noticeable differences in the NTCP of the heart, lung, and skin. Conclusion: If MC is more accurate than PB as reported in the literature, dosimetric and radiobiological results from the current study suggest that PB overestimates the target dose, EUD, and TCP for IMPT breast cancer treatment. The overestimation of dosimetric and radiobiological results of the target volume by PB needs to be further interpreted in terms of clinical outcome.

Investigating volumetric repainting to mitigate interplay effect on 4D robustly optimized lung cancer plans in pencil beam scanning proton therapy

“…Researchers are advocating the use of the Monte Carlo for dose calculations if the proton beam encounters low-and high-density interfaces in its path, such as in the case of lung cancer treatment, [1][2][3][4] as well as if the proton beam traverses a range shifter, which creates an air gap between the distal end of the range shifter and patient body. [5][6][7] The second challenge in treating lung cancer with the PBS proton beam is the interplay effect between dynamic pencil proton beams and motion of the lung tumor. [8][9][10][11][12][13][14][15][16][17][18][19] To mitigate the interplay effect in proton therapy, several strategies have been proposed.…”

“…Monte Carlo dose calculation engines are becoming available in the commercial treatment planning systems (TPSs). Researchers are advocating the use of the Monte Carlo for dose calculations if the proton beam encounters low‐ and high‐density interfaces in its path, such as in the case of lung cancer treatment, 1–4 as well as if the proton beam traverses a range shifter, which creates an air gap between the distal end of the range shifter and patient body 5–7 . The second challenge in treating lung cancer with the PBS proton beam is the interplay effect between dynamic pencil proton beams and motion of the lung tumor 8–19 .…”

Implications of Radiosensitizer and Radioprotector Factors in Refining the Dose-Volume Constraints and Radiobiological Models

“…Biological optimization based on NTCP of treatment plans has become a feasible alternative, based on dose-volume optimization, demonstrating the possibility to reduce up to 3 times the doses received by the parotid glands in the case of locally advanced nasopharynx cancers treated by IMRT technique [16,17].…”

“…TCP and NTCP radiobiological models can be used to evaluate the effect of systematic and random errors on the probability of tumor control and on the risk of toxicity, using information from the DVH curves. Some authors have used EPID portal dosimetry to check the dose received by critical organs as heart for the purpose of evaluating NTCP [2,[16][17][18].…”

Evaluation of Surgical Effect of Atrial Septal Defect with Tricuspid Regurgitation by Transesophageal 3D Echocardiography Based on MC Image Reconstruction Algorithm

“…TR blood enters the right atrium from the right ventricle via the insufficient TR. TR is usually secondary to the right ventricular dilatation and single dilatation or single high pressure due to severe pulmonary hypertension or right ventricular outflow tract obstruction [2]. At this stage, the clinical assessment of ASD mainly relies on coronary angiography, intravascular ultrasound, and optical coherence tomography [3,4].…”