Reducing Heart dose during Left Breast Cancer Radiotherapy: Comparison among 3 Radiation Techniques

Dosimetric comparison of different intensity-modulated radiotherapy techniques for whole-breast irradiation of right-breast cancer

PURPOSE

This study compared the dosimetric parameters of field-in-field forward intensity-modulated radiotherapy (FIF-IMRT) and fixed-field inversely optimized intensity-modulated radiotherapy (FFIO-IMRT) for the whole-breast irradiation of patients undergoing right-breast lumpectomy.

MATERIAL AND METHODS

A total of 30 patients with pT1-2N0M0 right-breast invasive ductal carcinoma were enrolled in this study. Two different treatment plans, i.e., FIF-IMRT and FFIO-IMRT, were designed for each patient. The dosimetric parameters of the two treatment plans were compared including ipsilateral lung and heart, conformity index (CI), and the homogeneity index (HI) of the planning target volume (PTV).

RESULTS

Fixed-field inversely optimized intensity-modulated radiotherapy was found to significantly improve CI (83.302% vs. 60.146%) and HI (11.837% vs. 19.280%), and significantly reduced V₂₅ (18.038% vs. 19.653%) and V₃₀ (15.790% vs. 18.492%) of the ipsilateral lung. It also significantly increased V₅ (69.791% vs. 32.615%) of the ipsilateral lung and V₅ (61.579% vs. 3.829%), V₁₀ (14.130% vs. 0.381%), V₂₀ (1.843% vs. 0.051%), and D_mean (5.211Gy vs. 1.870Gy) of the heart.

CONCLUSION

Regardless of improving the conformity and homogeneity of PTV and reducing the ipsilateral lung irradiation volume at high doses, FFIO-IMRT significantly raised the ipsilateral lung irradiated volume at low doses, as well as the irradiation volume and mean radiation doses to the heart. This limits its use in patients with early-stage right breast cancer.

The effect of respiratory capacity for dose sparing in left-sided breast cancer irradiation with active breathing coordinator technique

Background and aim

A subsequent cardiac toxicity is deemed to be dose-dependent for left-sided breast cancer irradiation. This study aims to demonstrate the effect of respiratory capacity for dose sparing when the deep inspiration breath hold with Active Breathing Coordinator technique (ABC-DIBH) is used in left-sided breast cancer irradiation.

Methods

74 left-sided breast cancer patients, who received whole breast or post-mastectomy chest wall radiotherapy with ABC-DIBH between 2020 and 2021 in our center, were retrospectively reviewed in this study. CT scans of free breath (FB) and ABC-DIBH were done for each patient, and two treatment plans with a prescription dose of 5000 cGy/25 Fr were designed separately. The dose to heart, left anterior descending artery (LAD) and lungs was compared between FB and ABC-DIBH. The correlation between individual parameters (dose to organs at risk (OARs) and minimum heart distance (MHD)) was analyzed, and the effect of respiratory capacity for dose sparing was assessed.

Results

The plans with ABC-DIBH achieved lower Dmean for heart (34.80%, P < 0.01) and LAD (29.33%, P < 0.01) than those with FB. Regression analysis revealed that both Dmean and D2 of heart were negatively correlated with MHD in the plans with FB and ABC-DIBH, which decreased with the increase in MHD by 37.8 cGy and 309.9 cGy per 1mm, respectively. Besides, a lower Dmean of heart was related to a larger volume of ipsilateral lung in plans with FB. With the increase in volume of ipsilateral lung, the linear correlation was getting weaker and weaker until the volume of ipsilateral lung reached 1700 cc. Meanwhile, a negative linear correlation between Dmean of LAD and MHD in plans with FB and ABC-DIBH was observed, whose slope was 162.5 and 135.9 cGy/mm, respectively. Furthermore, when the respiratory capacity of ABC-DIBH reached 1L, and the relative ratio (ABC-DIBH/FB) reached 3.6, patients could obtain the benefit of dose sparing. The larger difference in respiratory capacity had no significant effect in the larger difference of MHD, Dmean of heart and Dmean of LAD between FB and ABC-DIBH.

Conclusion

This study demonstrates the sufficiently good effect of ABC-DIBH when utilizing for cardiac sparing. It also reveals the correlations among individual parameters and the effect of respiratory capacity for dose sparing. This helps take optimal advantage of the ABC-DIBH technique and predict clinical benefits.

Association Between Radiotherapy and Death From Cardiovascular Disease Among Patients With Cancer: A Large Population‐Based Cohort Study

Background

This study aimed to investigate the association between radiotherapy for cancer and cardiovascular disease (CVD) deaths and evaluate the relative risk for CVD deaths in the general population and among patients with cancer treated with radiotherapy.

Methods and Results

The statistics of cancers from 16 sites were extracted from the Surveillance, Epidemiology, and End Results database and evaluated. Multivariable Cox proportional hazards regression analysis was used to analyze the association between radiotherapy and cardiovascular‐specific survival. The standardized mortality ratio for CVD deaths was estimated by comparing the observed deaths of patients with cancer treated with radiotherapy to the expected deaths of the general population. Of the 2 214 944 patients identified from the database, 292 102 (13.19%) died from CVD. Multivariable Cox proportional hazards regression analyses demonstrated that radiotherapy was an independent risk factor for cardiovascular‐specific survival among patients with lung and bronchus, cervix uteri, corpus uteri, and urinary bladder cancers. The long‐term cardiovascular‐specific survival of patients with cancer who underwent radiotherapy was significantly lower than that of patients who did not undergo radiotherapy. The incidence of CVD deaths among patients with lung and bronchus, cervix uteri, corpus uteri, and urinary bladder cancers who underwent radiotherapy was higher than that among the general population. Standardized mortality ratio significantly decreased with increasing age at cancer diagnosis, gradually decreased within 10 years of diagnosis and increased after 10 years of diagnosis.

Conclusions

Radiotherapy is associated with worse cardiovascular‐specific survival in patients with lung and bronchus, cervix uteri, corpus uteri, and urinary bladder cancers. Long‐term surveillance of cardiovascular conditions should be performed after radiotherapy.

Dosimetric evaluation and systematic review of radiation therapy techniques for early stage node-negative breast cancer treatment

Radiation therapy (RT) is essential in treating women with early stage breast cancer. Early stage node-negative breast cancer (ESNNBC) offers a good prognosis; hence, late effects of breast RT becomes increasingly important. Recent literature suggests a potential for an increase in cardiac and pulmonary events after RT. However, these studies have not taken into account the impact of newer and current RT techniques that are now available. Hence, this review aimed to evaluate the clinical evidence for each technique and determine the optimal radiation technique for ESNNBC treatment. Currently, six RT techniques are consistently used and studied: 1) prone positioning, 2) proton beam RT, 3) intensity-modulated RT, 4) breath-hold, 5) partial breast irradiation, and 6) intraoperative RT. These techniques show dosimetric promise. However, limited data on late cardiac and pulmonary events exist due to challenges in long-term follow-up. Moving forward, future studies are needed to validate the efficacy and clinical outcomes of these current techniques.

[Establishing margins from CTV to PTV in breast cancer treatment]

The benefit of postoperative radiotherapy for breast cancer both in terms of local control and overall survival is widely acknowledged. Today, technological advances in simulation imaging and positioning control enable the definition of new margins from CTV to PTV. Improvements in mathematical modeling of random and systematic errors impact the treatment plans. However, there is no universal absolute value to consistently determine the margins from CTV to PTV. It is down to each centre to assess and correct as much as possible uncertainties due to positioning and internal movements depending on techniques and methods used for the implementation of treatment and monitoring. IMRT and respiratory gating techniques for breast radiotherapy will be considered more systematically in the years to come.