Hybrid planning techniques for early-stage left-sided breast cancer: dose distribution analysis and estimation of projected secondary cancer-relative risk

Iga Racka; Karolina Majewska; Janusz Winiecki; Karolina Kiluk

doi:10.1080/0284186X.2023.2238553

Hybrid planning techniques for early-stage left-sided breast cancer: dose distribution analysis and estimation of projected secondary cancer-relative risk

Acta Oncol. 2023 Aug;62(8):932-941. doi: 10.1080/0284186X.2023.2238553. Epub 2023 Jul 30.

Authors

Iga Racka¹, Karolina Majewska¹, Janusz Winiecki^{1

2}, Karolina Kiluk³

Affiliations

¹ Medical Physics Department, Prof. Franciszek Łukaszczyk Memorial Oncology Center, Bydgoszcz, Poland.
² Clinic of Oncology and Brachytherapy, Collegium Medicum in Bydgoszcz, Nicholas Copernicus University, Torun, Poland.
³ Independent Researcher, Bydgoszcz, Poland.

PMID: 37516978
DOI: 10.1080/0284186X.2023.2238553

Abstract

Purpose: The purpose of this study was to evaluate three techniques of irradiation of left-sided breast cancer patients, three-dimensional conformal radiotherapy (3D-CRT), hybrid Intensity-Modulated Radiotherapy (h-IMRT), and hybrid Volumetric-Modulated Arc Therapy (h-VMAT, h-ARC), in terms of dose distribution in the planning target volume (PTV) and organs at risk (OARs). The second aim was to estimate the projected relative risk of radiation-induced secondary cancers for hybrid techniques.

Materials and methods: Three treatment plans were prepared in 3D-CRT, h-IMRT, and h-VMAT techniques for each of the 40 patients, who underwent CT simulation in deep inspiration breath-hold (DIBH). For hybrid techniques, plans were created by combining 3D-CRT and dynamic fields with an 80%/20% dose ratio for 3D-CRT and IMRT or VMAT. Cumulative dose-volume histograms were used to compare dose distributions within the PTV and OARs (heart, left anterior descending coronary artery [LAD], left and right lung [LL, RL], right breast [RB]). Projected risk ratios for secondary cancers were estimated relative to 3D-CRT using the organ equivalent dose (OED) concept for the Schneider's linear exponential, plateau, and full mechanistic dose-response model.

Results: All plans fulfilled the PTV criterium: V95%≥95%. Compared to 3D-CRT, both hybrid techniques showed significantly better target coverage (PTV: V95%>98%, p < 0.001), and the best conformality was achieved by h-ARC plans (CI: 1.18 ± 0.09, p < 0.001). Compared to 3D-CRT and h-ARC, h-IMRT increased the average sum of monitor units (MU) over 129.9% (p < 0.001). H-ARC increased the mean dose of contralateral organs and the LL V5Gy parameter (p < 0.001). Both hybrid techniques significantly reduced the D_max of the heart by 5 Gy. Compared to h-IMRT, h-ARC increased secondary cancer projected relative risk ratios for LL, RL, and RB by 18, 152, and 81%, respectively.

Conclusions: The results confirmed that both hybrid techniques provide better target quality and OARs sparing than 3D-CRT. Hybrid VMAT delivers less MU compared to hybrid IMRT but may increase the risk of radiation-induced secondary malignancies.

Keywords: 3D-CRT; Breast cancer radiotherapy; deep inspiration breath hold; hybrid-IMRT; hybrid-VMAT; secondary cancer.

MeSH terms

Breast Neoplasms* / radiotherapy
Female
Humans
Neoplasms, Radiation-Induced*
Neoplasms, Second Primary* / etiology
Organs at Risk / radiation effects
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods
Radiotherapy, Conformal* / adverse effects
Radiotherapy, Conformal* / methods
Radiotherapy, Intensity-Modulated* / adverse effects
Radiotherapy, Intensity-Modulated* / methods
Risk
Unilateral Breast Neoplasms* / radiotherapy