Influence of different boost techniques on radiation dose to the left anterior descending coronary artery

Which Patients with Left Breast Cancer Should be Candidates for Heart-Sparing Radiotherapy?

Purpose

This study aimed to identify risk factors that have significant interaction with radiation exposure to the heart, and thus to determine candidates for heart-sparing radiotherapy (RT) among women with left breast cancer.

Methods

We identified 4,333 patients who received adjuvant RT following breast-conserving surgery for ductal carcinoma in situ or invasive breast cancer from 1996 to 2010. Incidence rates of cardiovascular disease were compared between left-sided and right-sided RT, and stratified by age and risk factors such as body mass index (BMI), smoking, hyperlipidemia, hypertension, diabetes, administration of anthracycline, and trastuzumab.

Results

In all patients, the cumulative incidence of cardiovascular disease was greater in patients treated with left-sided RT than in those treated with right-sided RT, but the difference was not significant (p=0.428). Smoking (hazard ratio [HR], 5.991; 95% confidence interval [CI], 2.109-17.022; p=0.002) and hyperlipidemia (HR, 5.567; 95% CI, 3.235-9.580; p<0.001) were the most powerful risk factors for cardiovascular disease. There was no significant factor that further increased the risk of cardiovascular disease after left breast RT compared to right breast RT.

Conclusion

Although hyperlipidemia and smoking are risk factors for cardiovascular disease, they have not been proven to increase the risk of RT-related cardiovascular disease in Korean women.

Dosimetric comparison of simultaneous integrated boost with whole-breast irradiation for early breast cancer

Purpose

The purpose of this study was to identify a more suitable boost plan for simultaneously integrated boost scheme in patients with breast cancer by comparing among 3 types of whole-breast irradiation plus tumor bed boost plans.

Methods

Twenty patients who received radiotherapy following breast-conserving surgery for early breast cancer were enrolled in this study. We performed 1 type of electron plan (E1P plan) and 2 types of 3-dimensional conformal plans using a photon (P3P and P5P plans). The dosimetric parameters for the heart, total lung and the target volume between the 3 treatment types were compared.

Results

For the tumor bed, the difference in the mean dose between the 3 plans was maximally 0.1 Gy. For normal breast parenchyma, the difference in the mean dose between the 3 plans was maximally 1.1 Gy. In the dose range over the prescribed dose of 51 Gy, V₅₅ and V₆₀ in the E1P plan were lower than those in the P3P and P5P plans, which indicated that the E1P plan was more suitable than the P3P and P5P plans. In case of the heart and total lung, the values of clinically important parameters were slightly higher in the E1P plan than in the P3P and P5P plans. However, these differences were less than 2%.

Conclusion

We observed that a simple electron plan for tumor bed boost is preferable over multi-field photon plans in terms of the target volume coverage and normal tissue sparing.

Accelerated whole breast irradiation in early breast cancer patients with adverse prognostic features

Purpose

Accelerated whole breast irradiation (AWBI) and conventional whole breast irradiation (CWBI) were compared to determine whether AWBI is as effective as CWBI in patients with early breast cancer and adverse prognostic features.

Patients and methods

We included 330 patients who underwent breast-conserving surgery (BCS) and post-operative radiation therapy (RT) using AWBI for pT1-2 and pN0-1a breast cancer from 2007 to 2010. These patients were matched with 330 patients who received CWBI according to stage, age (±3 years), and the year of BCS. AWBI of 39 Gy and CWBI of 50.4 Gy were given in 13 and 28 fractions, respectively.

Results

Median follow-up time was 81.9 months. There were no statistically significant differences between the AWBI and CWBI groups in terms of age, stage, tumor grade, or molecular subtype. More patients with Ki-67 index ≥ 14% were present in the AWBI group (AWBI 47.0% vs. CWBI 10.3%; P<0.01). The 5-year ipsilateral breast tumor relapse (IBTR) rates for the AWBI and CWBI groups were 0.8% and 1.8%, respectively (P=0.54). High tumor grade was a statistically significant risk factor for IBTR (5-year IBTR rate: 2.9%; P=0.01). Ki-67 ≥ 14% was marginally related to IBTR (5-year IBTR rate: 2.2%; P=0.07). There were no statistically significant differences in the hazard ratios between the AWBI and CWBI groups according to any of the risk factors. There were no acute grade 3 toxicities in the AWBI group. There were no late grade 3 toxicities in either group.

Conclusions

AWBI is comparable to CWBI in early breast cancer with adverse prognostic features.