Modern Rotational Radiation Techniques with Volumetric Modulated Arc Therapy or Helical Tomotherapy for Optimal Sparing of the Lung and Heart in Left-Breast Cancer Radiotherapy Plus Regional Nodal Irradiation: A Comparative Dosimetric Analysis

Abstract

Background: For advanced breast cancer with lymph node involvement, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. However, an extensive RT volume is associated with normal organ exposure, which increases the toxicity and affects patient outcomes. Modern arc RT techniques can improve normal organ sparing compared with conventional techniques. The aim of this study was to explore the optimal technique for left-breast RT with RNI. Methods: We retrospectively reviewed patients receiving RT with RNI for left-breast cancer. We used modern arc RT techniques with either volumetric-modulated arc therapy (VMAT) or helical tomotherapy (HT) with a novel block technique, and compared differences in dosimetry parameters between the two groups. Subgroup analysis of RNI with or without internal mammary node (IMN) volume was also performed. Results: A total of 108 eligible patients were enrolled between 2017 and 2020, of whom 70 received VMAT and 38 received HT. The median RT dose was 55 Gy. No significant differences were found regarding the surgery, RT dose, number of fractions, target volume, and RNI volume between the VMAT and HT groups. VMAT reduced the heart mean dose more than HT (3.82 vs. 5.13 Gy, p < 0.001), as well as the cardiac parameters of V5-V20, whole-lung mean dose, lung parameters of V5-V20, and contralateral-breast and esophagus mean dose. In the subgroup analysis of RNI with IMNs, the advantage of VMAT persisted in protecting the heart, lung, contralateral breast, and esophagus. HT was beneficial for lowering the thyroid mean dose. For RNI without IMN, VMAT improved the low-dose exposure of the heart and lung, but HT was similar to VMAT in terms of heart, whole-lung, and contralateral-breast mean dose. Conclusions: For patients with left-breast cancer receiving adjuvant RT with RNI, VMAT reduced the exposure dose to the heart, lung, contralateral breast, and esophagus compared with HT. VMAT was superior to HT in terms of normal organ sparing in the patients who underwent RNI with IMN irradiation. Considering the reduction in normal organ exposure and potential toxicity, VMAT is the optimal technique for patients receiving RNI when deep inspiration breath-hold is not available.

Modulation of Secondary Cancer Risks from Radiation Exposure by Sex, Age and Gonadal Hormone Status: Progress, Opportunities and Challenges

“…Finally, the use of external ionizing radiation for therapy is not limited to cancer [ 4 , 52 , 53 , 54 , 55 ]. In this regard, it is noteworthy that extended follow-up of individuals administered X-ray therapy to treat tinea capitis in children revealed a significant increase in risk of thyroid cancer, with the excess risk being up to 4-fold higher in females relative to males [ 4 , 53 ].…”

“…The authors report that for both thyroid cancers and adenomas the absolute excess risk per rad was two to three times as great in females relative to males. An increased risk of breast cancer was noted as well [ 52 , 55 ].…”

Comparative dosimetric and radiobiological assessment of left-sided whole breast and regional nodes with advanced radiotherapy techniques

“…Compared with previous studies of VMAT and HT plans, the dose to the ipsilateral lung was lower [ 16 , 18–24 ]. The mean doses were 13.5 ± 1.0 Gy according to Pasler [ 16 ], 14.4 ± 1.4 Gy according to Boman [ 18 ], 14.0 ± 3.4 according to Osman [ 19 ], 14.6 ± 0.6 Gy according to Pasler [ 20 ], 13.6 ± 1.4 Gy in VMAT and 13.6 ± 1.2 Gy in HT plans according to Lauche [ 22 ], 12.77 ± 1.29 Gy according to Yeh [ 23 ], 9.61Gy in VMAT and 11.04 Gy in HT plans according to Hou [ 24 ].…”