Identifying breast cancer patients who gain the most dosimetric benefit from deep inspiration breath hold radiotherapy

Abstract

Introduction: Deep inspiration breath hold (DIBH) has been proven to reduce cardiac dose for women receiving left breast and chest wall radiation therapy. However, it utilises extra departmental resources and patient exertion. The aim of this exploratory study was to investigate if any factors existed that could identify breast cancer patients who may benefit most from DIBH, to facilitate appropriate utilisation of departmental resources. Methods: Left-sided breast cancer patients aged 18-70 years, and right-sided breast cancer patients with internal mammary nodes included, were recruited. DIBH and free breathing (FB) plans were created for all patients. Patient demographic and clinical history were recorded. Variables including lung threshold value, lung volume, patient separation, maximum heart in field, volume of planning target volume (PTV), heart dose, ipsilateral lung dose were compared between plans. Results: Plans for 31 patients were analysed. No correlations were found between lung threshold value or patient separation and cardiac dose. Moderate to strong correlations were found with BMI, PTV volume and lung volume change however no definitive thresholds were determined. A significant difference was found in the maximum heart in field between DIBH and FB (P < 0.001) with those patients with greater than 0.7 cm heart in the field on the FB scan demonstrating greater reductions in mean heart dose. Conclusion: Maximum heart in the field of greater than 0.7 cm in FB could be a potential factor to identify patients who may benefit most from DIBH. This factor warrants investigation in a larger patient cohort to test its validity.

Preoperative spirometry and BMI in deep inspiration breath-hold radiotherapy: the early detection of cardiac and lung dose predictors without radiation exposure

“…In this study, we investigated the relationship of non-CT parameters to MHD and MLD in DIBH. Although BMI and PFT have also been used as exploring parameters in previous studies [ 14 , 27 – 32 ], this study used only preoperative information for the first time. Thus, the prediction results can be extrapolated earlier, which may help determine the initial surgical treatment or postoperative radiotherapy.…”

“…Also, the parameters of this study were obtained as a routine workup, so additional patient burden or radiation exposure would not occur. Compared to the previous studies that used non-CT parameters as described in Table 3 [ 14 , 27 – 32 ], this study has some strong points: a large sample size, investigating the relationship to MLD as well as MHD.…”

“…Compared to the previous studies that used non-CT parameters as described in Table 3 [ 14 , 27 – 32 ], this study has some strong points: a large sample size, investigating the relationship to MLD as well as MHD.…”

“…Statistical analysis was performed using R version 3.6.1 (The R Foundation for Statistical Computing, Vienna, Austria). The correlation between the covariates and the objective variables (MHD or MLD) was tested using Pearson's s correlation coefficient; r. The required sample size was calculated as follows: Past studies showed r = − 0.25 to − 0.81 between covariates and MHD [ 14 , 27 – 32 ], and if this study shows the minimum r = − 0.25, ninety-seven patients were required with alpha = 0.05 and power = 0.80. The significantly correlated factors with MHD or MLD will be examined using multivariable analyses.…”

“…Several studies have attempted to identify suitable patients or predict MHD in DIBH using anatomical information based on the simulation CT (e.g., maximum cardiac distance, cardiac contact distance) [ 14 – 26 ]. However, some non-CT parameters such as BMI or pulmonary function test results (PFT) are also reported to correlate to MHD [ 14 , 27 – 32 ]. Such non-CT parameters may have the advantage of being available earlier without additional burden or radiation exposure to the patient.…”