Analysis Of Coronary Artery Dosimetry In 3- Dimensional Era In Left Sided Tangential Breast Radiation.

Background: Radiotherapy for breast cancer often involves some incidental exposure of the heart to ionizing radiation. The aim of the study: To evaluate the dose received by the left anterior descending coronary artery (LAD), correlate it with cardiac dose & acute cardiac toxicity in relation to the dose received by LAD within first 2 months following RT to left sided breast cancer. Patients and Methods: This prospective study included 26 left sided breast cancer patients who operated with breast conservative surgery, all of them had to have the inclusion criteria of histologically proven invasive breast carcinoma.,T1-T2 tumor.,Stage I-II.,No previous radiotherapy.,No history of contralateral breast cancer.,No medical comorbidities, and received adjuvant chemotherapy. Patients evaluated pretreatment by: Medical history, complete physical examination &Cardiologic consultation., Laboratory evaluation: Complete blood count, Liver, kidney function tests and serum CA, CA 15-3. Radiological evaluation: Chest x-ray, Pelvi-abdominal ultrasound. Bone scan.,Evaluation of cardiac status, e.g. ECG, ECHO. Treatment protocol: Patients were simulated using the CT - planning system, target volumes and organ at risk were contoured. The detailed dosimetry of target volumes and organ at risk were obtained and analyzed. Treatment evaluation and follow up: Patients were evaluated weekly during treatment for cardiac, hematological, skin, lung toxicities and after completing RT by 2 months according to the WHO grading system. The results: The mean age was 47.80 ± 10.17., 42.3% of patients were premenopausal, while postmenopausal women represented 38.5%, The primenopausal women were represented by 19.2%. Tumor characteristics: Histopathological grade II was 69.2% and grade III was 30.8%.All tumors were T1 and T2; T1 and T2 represented 42.3%, 57.7% respectively. Stage II represented 73% FAC was the commonest chemotherapy used in 53.8%, while patients received AC Taxol &FEC regimens represented 23.1%, 23.1% respectively. Significant direct correlation was found between mean LAD dose and mean heart dose with Regression line equation: Mean LAD Dose (cGy) = 4.24 x Mean Heart Dose (cGy). And we couldn\'t identify acute heart toxicity. The mean LAD dose was 15.8 Gy. The mean heart dose was 3.5 Gy and median V25 was 2.7%., For every 1 Gy increase in mean heart dose, mean LAD dose increased by 4.24 Gy. For every percent increase in the heart V10 and V25 there was a 2.24 Gy and 3.74 Gy increase in mean LAD dose, respectively . For every percent increase in the heart V40 a 5.06 Gy increase in mean LAD dose was noted and for every percent increase of heart V25 a 5.16% increase in the LAD V20 was demonstrated. There was no significant association between central lung distance, min and Mean LAD Dose, while there is a direct correlation between CLD and Max LAD Dose. There was no significant association between heart volume, mean and max LAD dose, while there is a direct correlation between heart volume and min LAD dose. Conclusion: Clear excellent correlation between the dose to the heart and LAD artery was discovered., So LAD artery does not need to be contoured separately when standard tangential borders are used.