Thirty radiation plans from 15 patients were evaluated in the current analysis: 15 in DIBH and 15 in FB. All participants met the criteria for neoadjuvant radiotherapy (either T3 tumor and/or node positive) including 9 patients with squamous cell histology and 6 patients with adenocarcinoma histology (Table 1). Twelve patients underwent PET scans for radiation planning within 1 week of P‑CT, which were used to assist in target volume delineation.

The average volume of PTV in DIBH was 342.09 cm3 (SD ± 144.12), while for FB it was 363.73 cm3 (SD ± 132.76), with a p-value of 0.088. Dosimetric parameters assessing target volume coverage—including D2%, D98%, D50%, and V95%—demonstrated comparable results between DIBH and FB plans (Table 2). The mean HI was consistent at 1.1 for both cohorts (p-value: 0.125). Additionally, the average CI was 1.02 for plans in DIBH and 1.03 for plans in FB (p-value: 0.33), suggesting similar conformity. The average monitor units per plan showed no significant variance, with 507.7 for DIBH and 535.23 for FB (p-value: 0.107).

The mean cardiac volume was significantly reduced in DIBH compared to FB, with values of 831.5 cm3 and 885.4 cm3, respectively (p-value: 0.012). Similarly, the average mean dose to the heart (heart Dmean) was significantly lower in DIBH-plans, at 6.21 Gy, compared to 7.02 Gy in FB-plans (p-value: 0.011). Moreover, V30 Gy and D2% of the heart in DIBH (5% and 35.28 Gy) were significantly lower than FB (5.8% and 35.84 Gy), with p-values 0.048 and 0.047, respectively (Fig. 1, Table 3).

Boxplot showing the heart Dmean (a), V30 (b), and D2% (c) irrespective of tumor location; heart Dmean (d), V30 (e), and D2% (f) for middle esophageal (ME) tumors; and lung Dmean (g, i) and V20 (h, j) irrespective of tumor location and for middle esophageal (ME) tumor, respectively, between the deep-inspiration breath hold plans (DIBH) in blue and free breathing plans (FB) in orange, asterisk P-value < 0.05

Regarding the dosimetric impact on cardiac chambers, DIBH plans demonstrated a significantly lower Dmean to the LV compared to FB plans, with a mean dose of 4.27 Gy versus 5.12 Gy, respectively (p-value: 0.0018). Also, V10 and V20 Gy of LV were reduced in DIBH, with 8.5% compared to 11.5% and 2.6% versus 4% in FB, with p-values of 0.011 and 0.079, respectively. However, for the right ventricle and both atria, no significant differences in dose–volume metrics were observed between the DIBH and FB plans (Fig. 2, Table 3).

Linear diagrams representing relative volume in relation to dose for the right ventricle (a), left ventricle (b), right atrium (c), left atrium (d), left coronary (e), left anterior descending (f), left circumflex (g), and right coronary artery (h) in deep-inspiration breath hold (DIBH) and free breathing (FB) for both the entire cohort and middle third esophageal tumor (ME)

The Dmean and D2% of the LCA were significantly lower in DIBH at 3 Gy and 3.4 Gy compared to FB at 3.4 Gy and 5.5 Gy, with p-values of 0.019 and 0.021, respectively. Additionally, planning in DIBH yielded lower Dmean and D2% for the RCA at 2.23 Gy and 3.86 Gy, as opposed to 2.99 Gy and 4.96 Gy in FB, with p-values of 0.064 and 0.03, respectively (Table 3). The dosimetric parameters for the other coronary arteries did not demonstrate any significant differences between the FB and DIBH plans (Fig. 2, Table 3).

Further, the mean lung volume was higher for DIBH compared to FB (5138 vs. 3605 cm3, p-value < 0.00001), and this was linked to a significantly reduced Dmean in DIBH vs. FB, 10.3 vs. 10.8 Gy (p-value: 0.047; Fig. 1, Table 3).

Next, we analyzed the dosimetric parameters based on tumor location, where the tumor location was categorized into middle esophageal (ME) or distal esophageal (DE) tumors (proximal edge of the tumor < 32 vs. > 32 cm from the incisor teeth, respectively). When planning in DIBH versus FB for ME tumors, we observed a significant improvement in heart Dmean (6.02 vs. 7.13 Gy, p-value 0.007) and heart V30 Gy (5.3% vs. 6.6%, p-value 0.017), along with a reduction in heart D2% (34.99 Gy vs. 35.8 Gy, p-value 0.064). Moreover, the LV demonstrated significantly lower Dmean, D2%, V10, and V20 Gy in DIBH (3.79 Gy, 14.19 Gy, 6.8%, and 2%, respectively) compared to FB (4.85 Gy, 16.82 Gy, 11%, and 4%, respectively), with respective p-values of 0.0018, 0.041, 0.014, and 0.035. The RA exhibited a reduced Dmean and D2% in DIBH (5.73 Gy and 18.6 Gy) compared to FB (7.11 Gy and 24.02 Gy), with p-values of 0.087 and 0.019. For ME tumors, DIBH planning yielded lower Dmean and D2% for the LCA (3.14 vs. 3.54 Gy and 3.55 vs. 5.88 Gy, p-values 0.016 and 0.067, respectively), lower Dmean and V20 for the LCX (11.4 vs. 13.1 Gy, 21% vs. 28%, p-values 0.09 and 0.025 respectively), and decreased Dmean and D2% for the RCA (1.6 vs. 2.1 Gy, 2.15 vs. 3.03 Gy, p-values 0.057 and 0.046, respectively).

Nonetheless, the Dmean and V20 Gy of the lung in DIBH were 11.6 Gy and 18.2%, and in FB they were 12.5 Gy and 20.2%, with p-values of 0.0013 and 0.067, respectively.

Conversely, planning in DIBH for DE tumors only had a dosimetric advantage with regard to D2% of the LAD (2.52 Gy vs. 2.88, p-value 0.015) and a trend for improved V20 and V30 of LCX in FB compared to DIBH (50% vs. 29.7% and 37% vs. 14.5%, p-value: 0.059 and 0.059, respectively). All other cardiac, subcardiac, or pulmonary parameters evidenced comparable outcomes for DIBH and FB.