Abstract
The purpose of this study was to evaluate the radiobiological implications of clinical use of respiratory-gated techniques for postoperative radiation therapy of early-stage left-sided breast cancer after breast-conserving surgery. Radiation therapy treatment plans of 80 patients with early-stage breast cancer (stage I-II), receiving whole breast irradiation after breast-conserving therapy, were analyzed. The control group consisting of 47 patients received standard radiation therapy, and the respiratory-gated group consisting of 33 patients received deep inspiration-gated radiation therapy. Normal tissue complication probabilities (NTCP) for cardiac mortality and for clinical radiation-induced pneumonitis were calculated for all patients included in present study, using relative seriality model. NTCP data were analyzed for 113 radiation therapy plans, which included free breathing plans for the respiratory-gated groups. Pneumonitis probability was 0.6% (range 0.0-2.8%) and 0.3% (0.0-1.2%) for control and respiratory-gated group, respectively. Cardiac mortality was 1.3% (0.0-5.0%) and 0.2% (0.0-2.8%) for control and respiratory-gated group, respectively. Using respiratory-gated radiation therapy, NTCP was reduced in comparison with the control group by 83% (P<0.00001) and by 55% (P=0.01270) for cardiac mortality and for clinical radiation-induced pneumonitis, respectively. Use of respiratory-gated radiation therapy, for postoperative treatment of early-stage breast cancer, significantly reduces excessive cardiac mortality probability and pulmonary complication probability, as compared to standard radiation therapy techniques. This is especially important from heart complication probability point of view, as cardiac mortality remains one of the important issues of postoperative breast irradiation in patients with early stage breast cancer.
Highlights
Radiotherapy is an essential part of breast-conserving therapy for patients with early stage breast cancer [1]
Using respiratory-gated radiation therapy, Normal tissue complication probabilities (NTCP) was reduced in comparison with the control group by 83% (P
Use of respiratory-gated radiation therapy, for postoperative treatment of earlystage breast cancer, significantly reduces excessive cardiac mortality probability and pulmonary complication probability, as compared to standard radiation therapy techniques. This is especially important from heart complication probability point of view, as cardiac mortality remains one of the important issues of postoperative breast irradiation in patients with early stage breast cancer
Summary
Radiotherapy is an essential part of breast-conserving therapy for patients with early stage breast cancer [1]. Randomized trials conducted with a large number of patients have shown that radiotherapy (RT) after breast-conserving surgery significantly reduces local recurrence rate [2, 3]. Results of studies with more than 20-year follow-up have proven that lumpectomy with adjuvant whole breast RT for patients with early stage breast cancer equals to mastectomy by local recurrence rate and overall survival [2, 4]. Recent meta-analysis of data of trials performed worldwide has shown that RT after breast-conserving surgery significantly increases patient survival [5]. Study by Buchholz et al demonstrated that for clinical stage II breast cancer, breast-conserving surgery with following RT provides statistically significant increase in survival, comparing to mastectomy without radiotherapy [6]. Vicini et al demonstrated that some distant metastases could directly develop from recurrence in ipsilateral breast, so supporting the importance of local tumor control in the overall treatment of patients with breast cancer [7]
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