Three-dimensional conformal partial breast external-beam irradiation after conservative surgery of the breast / 中华放射肿瘤学杂志

ABSTRACT

Objective To explore the methods, dosimetric features and short-term effects of partial breast irradiation carried out by three-dimensional external-beam irradiation (3DCPBI) assisted by active breathing control (ABC) . Methods Computed tomography (CT) simulation assisted by active breathing control (ABC) was carried out for each patient and intended to get CT images in condition of 75% deepest inspiration named moderate deep inspiration breath hold (mDIBH). The extent labeled by the silver slips located in the cavity was delineated as gross target volume (GTV) , GTV plus the margin of 15 mm was defined as planning target volume (PTV). 6 MV X-ray was selected as the radiation source and noncoplanar radiation with four three-dimensional conformal fields was used, the described dose was 34 Gy /10f/5d. The volume of GTV, PTV, the affected whole breast, and the percentage of PTV accounted for the affected whole breast , the percentages of PTV included by 100% , 95% and 90% isodose curve, the percentage of volume of the affected breast irradiated by 34. 0, 27. 2, 20. 4, 13. 6 and 6. 8 Gy , and Dmean,D5,V20 of the lungs and heart were calculated respectively. Acute radiation skin response was recorded and the cosmetic effect of the breast after radiotherapy were appraised, with the local tumor control and survival rate followed. Results The mean of volume ratio of PTV and affected whole breast was 14. 88% ; the mean of the volume covered by 90% isodose curve accounted for 92. 54% of the PTV; the volume irradiated by 34 Gy (100% of described dose) accounted for 17. 23% (mean) of the whole breast and 6. 8 Gy (20% of described dose) for 46. 11% , in other words, the volume covered by 20% of described dose was less than 50% of the whole breast. The Dmean, D5, V20 for the affected lateral lung were 1.97, 9. 25 Gy and 1. 58% , it was 0.20, 0. 87 Gy , and 0% for the unaffected lateral lung. The Dmean,D5, V20 for the heart was 0.65 Gy , 2. 82 Gy , and 0. 85%. Zero grade of acute radiation skin reaction was seen in 14 patients and gradel in 3 patients and there was not equal to or more than grade 2 of skin reaction for all the patients. Cosmetic effect were appeci-ated and satisfaction defined as excellent or good appearance of the irradiated breasts for all the patients. No recurrence of local tumor for all of the patients followed for one year. Therefore, the cosmetic result of 1 yr. follow - up was 100% and no recurence was found after 1 yr. follow - up. The 1-year tumor-free survival rate were all 100%. Conclusions For selected patients with early breast cancer after breast-conservative surgery, 3DCPBI assisted by ABC is feasible, however, the selection criteria for the patients, technique protocol and dose fractionation of 3DCPBI and its influence on late cosmetic effect, local tumor control and survival need to be continuously explored and observed in the future.