Evaluation of Cardiac Dose Reduction With Deep Inspiration Breath Hold in Patients With Left-Sided Breast Cancer Receiving Adjuvant Radiation Therapy

Dosimetric comparison between volumetric-modulated arc therapy and a hybrid volumetric-modulated arc therapy and segmented field-in-field technique for postmastectomy chest wall and regional lymph node irradiation

Decreasing radiotoxicity to the heart, lungs, and contralateral breast has proven to lower the risk of secondary malignancy and improve overall outcomes when treating chest wall (CW) and regional lymph nodes in postmastectomy breast cancer patients. In this retrospective study, 11 postmastectomy patients were selected and planned with a novel hybrid treatment method and a traditional volumetric arc therapy (VMAT) approach for comparison. This hybrid technique was able to optimize tangential beams to minimize heart dose and the VMAT contribution to improve dose conformity around the planning target volume (PTV). Overall, this hybrid technique produced more homogenous target dose coverage and demonstrated a decrease of integral dose to organs at risk (OAR), while the VMAT technique demonstrated a higher affinity for maintaining dose conformity. Further observation of dose distributions also revealed that the hybrid plans were more effective in sparing low-dose spread to healthy tissue in both right- and left-sided cases. This observation was made evident by the reduction in heart V5 and D_mean, decreases in all parameters regarding the contralateral lung, as well as all values other than the V20 of the ipsilateral lung. This unique hybrid planning technique could present an alternative to standard intensity-modulated radiation therapy (IMRT) planning when treating postmastectomy CW and regional lymph nodes, as it has shown the capacity to decrease cardiac, lung, and contralateral breast toxicity while maintaining quality PTV coverage.

The implementation of RapidPlan in predicting deep inspiration breath-hold candidates with left-sided breast cancer

The aim of this study is to determine if RapidPlan (RP) can be used as a prediction method to determine which left-sided supine breast cancer patients would benefit from the deep inspiration breath-hold (DIBH) technique. An RP model database was created with 72 clinically approved 3D conformal radiation therapy (3D-CRT) treatment plans. This model was validated by introducing 10 new patient data sets, creating RP-generated plans and comparing the clinically approved plan for the corresponding patient. The prediction ability of the model was then tested on the free-breathing (FB) scans of patients with clinically approved DIBH plans totaling 29 patients and results were then compared to the FB clinical plan attempts. A statistical analysis performed on the data indicated a strong correlation for the mean heart dose (R² = 0.914; p-value < 0.001) with a standard deviation of 48.6 cGy. After validating the link between physician PTV and mean heart dose, the model was tested clinically on 15 patients by inserting "Test PTV Evals" that were contoured by the researchers as a surrogate for predicting mean heart dose. Statistical analysis showed a strong correlation between the dose to 5% of the heart (D₅) and the mean heart dose (R² values of 0.913 and 0.881, respectively) with a standard deviation for the mean heart dose of 27.2 cGy. It was concluded that by using a Test PTV Eval, the RP-generated plans were able to predict mean heart doses within ± 30.0 cGy.