Dosimetric evaluation of the heart and left anterior descending artery dose in radiotherapy for Japanese patients with breast cancer

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Left-sided breast cancer requiring postoperative radiotherapy (n=32). Intervention: Two field-static intensity-modulated radiotherapy (2F-S-IMRT) vs. Four field-static IMRT (4F-S-IMRT), 40° dual partial arc VMAT (40d-VMAT), 80° dual partial arc VMAT (80d-VMAT), and 210° partial VMAT (210p-VMAT). Primary outcome: Percentage of the heart volume receiving 10 Gy or more (Heart V10) (p=<0.05).

Q: What does this research mean for the field?

Two field-static intensity-modulated radiotherapy (2F-S-IMRT) achieves superior cardiac and left anterior descending artery sparing with the lowest monitor units while maintaining adequate target coverage compared to other static IMRT and VMAT techniques in left-sided breast cancer radiotherapy. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Osamu Tanaka; Kousei Ono; Takuya Taniguchi; Chiyoko Makita; Masayuki Matsuo

doi:10.1093/jrr/rrz087

November 15, 2019Journal of Radiation ResearchOpen Access

Dosimetric evaluation of the heart and left anterior descending artery dose in radiotherapy for Japanese patients with breast cancer

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Why the study?

Few dosimetric comparison studies have evaluated intensity-modulated radiotherapy and volumetric modulated arc therapy in Japanese patients with breast cancer.

Does two field-static IMRT (2F-S-IMRT) reduce radiation dose to the heart and left anterior descending artery while maintaining planning target volume coverage compared to four-field IMRT and VMAT techniques in Japanese patients with left-sided breast cancer?

Key Points

To evaluate and compare radiation doses delivered to the heart and the left anterior descending artery across five different radiation planning techniques in patients with left-sided breast cancer.
Enrolled 32 patients with left-sided breast cancer receiving radiotherapy following breast-conserving therapy between July 2016 and June 2018 (trial registration: UMIN000035032).
Compared five radiotherapy plans per patient using free-breathing CT: two-field static IMRT (2F-S-IMRT), four-field static IMRT (4F-S-IMRT), 40° dual partial arc VMAT (40d-VMAT), 80° dual partial arc VMAT (80d-VMAT), and 210° partial VMAT (210p-VMAT).
Prescribed 50 Gy in 25 fractions to the planning target volume (PTV) and evaluated target coverage (D95), organ-at-risk exposure (V10 for heart and left anterior descending artery), and monitor units (MUs).
PTV D95 coverage was significantly lower in the 40d-VMAT plan (46.0 ± 1.3 Gy) than in all other treatment plans (P < 0.05), while 2F-S-IMRT achieved 48.0 ± 0.9 Gy.
Heart V10 was significantly lower for 2F-S-IMRT (9.3 ± 6.1%), 40d-VMAT (9.6 ± 6.7%), and 80d-VMAT (10.0 ± 6.7%) compared to 4F-S-IMRT (15.0 ± 8.8%) and 210p-VMAT (15.7 ± 10.3%, P < 0.05).
Left anterior descending artery V10 was significantly lower in 2F-S-IMRT (45.3 ± 10.7%), 40d-VMAT (47.3 ± 14.2%), and 80d-VMAT (46.0 ± 17.7%) than other plans, while 2F-S-IMRT required the fewest monitor units at 292.4 ± 20.7 MU (P < 0.05).

Study Design

Type

Observational (n=32)

Multicenter

No

Structured PICO

Does two field-static IMRT (2F-S-IMRT) reduce radiation dose to the heart and left anterior descending artery while maintaining planning target volume coverage compared to four-field IMRT and VMAT techniques in Japanese patients with left-sided breast cancer?

P

Population

32 Japanese patients with left-sided breast cancer who underwent postoperative radiotherapy as breast conserving therapy between July 2016 and June 2018.

I

Intervention

Two field-static intensity-modulated radiotherapy (2F-S-IMRT) prescribed at 50 Gy in 25 fractions (simulated on free-breathing planning CT)

C

Comparator

Four other simulated radiotherapy plans prescribed at 50 Gy in 25 fractions on the same patient CT datasets: four field-static IMRT (4F-S-IMRT), 40° dual partial arc volumetric modulated arc therapy (40d-VMAT), 80° dual partial arc VMAT (80d-VMAT), and 210° partial VMAT (210p-VMAT)

O

Outcome

Dosimetric parameters including planning target volume (PTV) D95 (level of coverage of PTV of 95% for irradiation at 50 Gy), homogeneity index (HI), and percentage of the heart and left anterior descending artery (LAD) volume receiving 10 Gy or more (V10)surrogate

Main Result

Absolute Event Rate: 9.3% vs 15.7%

p-value: p=<0.05

In Japanese patients with left-sided breast cancer undergoing free-breathing postoperative radiotherapy, two-field static IMRT provides optimal target coverage while minimizing radiation exposure to the heart, LAD, contralateral breast, and required monitor units compared to multi-field IMRT and VMAT.

Limitations

Simulation study conducted using free breath planning CT rather than deep inspiration breath-hold (DIBH) CT
Results may not apply to large-volume breasts as average PTV volume was 460 ± 149 cc
No patients with cardiac hypertrophy or funnel chest were included
Forward planning IMRT was not performed for comparison
Findings may not apply to patients with large breast volumes (average PTV volume was 460 ± 149 cc)
No patients with cardiac hypertrophy or funnel chest were included in the study
Forward planning IMRT (FP IMRT) was not performed

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Implication

2F-S-IMRT may reduce cardiac exposure in left breast RT planning; leaves open whether dosimetric gains improve clinical outcomes.

Abstract

Intensity-modulated radiotherapy (IMRT) has been used for breast cancer as well as in field-in-field techniques. Few dosimetric comparison studies have been conducted using IMRT and volumetric modulated arc therapy (VMAT) for Japanese patients. We aimed to study such patients. Thirty-two patients with left-sided breast cancer were enrolled. We conducted the following five treatment plans: two field-static IMRT (2F-S-IMRT), four field-static IMRT (4F-S-IMRT), 40° dual partial arc VMAT (40d-VMAT), 80° dual partial arc VMAT (80d-VMAT) and 210° partial VMAT (210p-VMAT). We evaluated the following: level of coverage of planning target volume (PTV) of 95% for irradiation at a dose of 50 Gy (D95) and the percentage of the heart and left anterior descending artery (LAD) volume that received 10 Gy or more (V10). As a result, the coverage of 40d-VMAT for the prescribed PTV dose of D95 was significantly lower than that of the other treatment plans (P < 0.05). Regarding heart V10 and LAD V10, 2F-S-IMRT, 40d-VMAT and 80d-VMAT showed significantly lower dose than the other treatment plans (P < 0.05). In conclusion, among the five plans, 2F-S-IMRT is recommended for Japanese patients because of high coverage of D95 of PTV, low V10 of the heart and LAD and the monitor unit value was the lowest.

Discussion

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Cite This Study

Tanaka et al. (2019) conducted an observational in Left-sided breast cancer requiring postoperative radiotherapy (n=32). Two field-static intensity-modulated radiotherapy (2F-S-IMRT) vs. Four field-static IMRT (4F-S-IMRT), 40° dual partial arc VMAT (40d-VMAT), 80° dual partial arc VMAT (80d-VMAT), and 210° partial VMAT (210p-VMAT) was evaluated on Percentage of the heart volume receiving 10 Gy or more (Heart V10) (p=<0.05).

synapsesocial.com/papers/6a92a8a12b6426cadba60ee0 https://doi.org/10.1093/jrr/rrz087

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Dosimetric evaluation of the heart and left anterior descending artery dose in radiotherapy for Japanese patients with breast cancer

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Dosimetric evaluation of the heart and left anterior descending artery dose in radiotherapy for Japanese patients with breast cancer

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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