Purpose: This work evaluates the use of target and organs at risk (OAR) dose-volume goals in 3D conformal radiotherapy (3DCRT) planning for node positive breast cancer (NPBC) patients undergoing regional nodal irradiation after lumpectomy/mastectomy. Methods: Dosimetric data for 262 NPBC patients receiving regional nodal and whole breast/chest wall (WB/CW) irradiation from 2000-2009 were analyzed. In all cases, target & OAR volumes were delineated on treatment CT scans for field generation and dose-volume histograms (DVHs) were generated. Cases were analyzed to identify how frequently they met treatment planning institutional dose-volume goals ("institutional guidelines" & standardized in 2005) and how this would affect OAR doses.
Background For NPBC patients the use of regional nodal irradiation (RNI) to the supraclavicular, axillary, internal mammary lymph nodes (IMN) in addition to the chest wall and/or breast can maximize locoregional control and improve overall survival. However, comprehensive RNI for breast cancers located on the left side has been linked to late cardiac morbidity, potentially lessening the therapeutic benefit of treatment. The optimal radiation dose-volume constraints for the heart in this setting are not fully understood. We examined NPBC patients treated with RNI using 3D-CT based radiation therapy (RT) to evaluate cardiac dose and incidence of cardiac events. Methods: Between 2000 and 2007, 150 NPBC patients were treated with RNI following lumpectomy or mastectomy using 3D-CRT. In all cases, treatment target and normal tissue volumes were delineated on treatment CT scans. The heart contour included the ventricles and the left atrium. The dose-volume histogram of the cardiac doses delivered and the incidence of cardiac events is reported. Results: Median follow-up of surviving patients is 7 (1-10.6) years. Median patient age is 50 (27-91). 52.35% are premenopausal, 75.7% estrogen receptor positive, 66.3% progesterone receptor positive and 15.92% HER-2 positive. Mean positive lymph nodes is 5 (1-29). Extracapsular extension is present in 47.31%. Mean microscopic tumor size is 3.73 (0.1-21) cm. The IMN receive > 40 Gy in 65.5%. 94% had chemotherapy, and in 82.3% it was anthracycline-based. At the time of RT, 12.2% smoked, 9.5% had diabetes, 32.4% with hypertension, and 4.7% with a history of coronary artery disease. There was 1 (0.7%) right sided patient with cardiac events and 4 (2.7%) left sided experiencing cardiac events (p = 0.121, Fisher's Exact test). A total of 10 cardiac diagnoses were experienced among the 5 patients: coronary artery disease with myocardial infarction (3), congestive heart failure (2), cardiomyopathy (2), and arrhythmia (3). The median time interval to onset of the events is 2.5 years (0-4.3 years). The cardiac doses among 150 patients are as follows: mean V25 is 5.7, (0.0 - 20.0%), V25 is < 9 % in 74.4% of patients, mean V45 is 1.8% (0-13.3%), V45 is < 5.5% in 91.8%. The mean maximum point dose is 42.8 Gy, and the mean heart dose is 5.6 Gy (0.2−25.3 Gy). The mean V25 and V45 in those 5 patients with a cardiac event is 6.7% (0.9−11.9%) and 3.7% (0-6.6%), respectively; in the 145 remaining patients, 5.7% (0-20.0%) and 1.7% (0-13.3%), respectively. The mean heart dose in those with an event is 5.2 Gy (2.4−7.3 Gy) versus 5.6 Gy (0.2−25.3 Gy) in the remaining patients. Conclusions: The cardiac event rate among these NPBC patients treated with RNI and anthracycline-based chemotherapy is low. However, those patients with cardiac events have a higher mean V45. No other dose-volume relationships are discernible. Additional analysis using 3DCRT volumes are important to validate these findings and better define the dose-volume parameters for cardiac toxicity. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-13-05.
130 Background: Regional nodal irradiation for lymph node (LN) positive BC after lumpectomy/mastectomy can be subject to controversy due to the potential for treatment morbidity particularly lymphedema. Little is known about lymphedema and other arm morbidity rates after 3DCRT approaches. Methods: 172 LN positive BC cases treated from 2000 to 2007 using 3-DCRT and Dose Volume Histogram analyses were studied. All cases underwent axillary node dissection (AND). Axillary target volumes (ATV) were delineated on all treatment planning CT scans. Field arrangement and beam modifications were selected to deliver a min of 45 Gy to 90% of the ATV. Post-treatment bilateral arm circumference measurements (96%) and patient reported ipsilateral arm symptoms (thickness, heaviness, tingling, numbness) were recorded. Results: Median follow-up was 83.7 months. Median (med) patient age was 50. 52% were premenopausal. 76/66% had positive estrogen/progesterone receptors and 16% were HER2+. 52% underwent lumpectomy and 46% mastectomy. Median number of LN removed was 17 (1-46), number +LN was 3 (1-29), and tumor size was 3.7 cm. For 79 patients with separate AND the mean resected axillary volume was 157.8 cc (med 171 cc, range 25-472 ). The mean contoured ATV was 69 cc (med 58cc, range 16-608). On average 95% of the ATV was covered by a med of 44.7 Gy. Local control was achieved in 94.7% regional LN control in 99.4%. 16.7% met criteria for lymphedema (> 2 cm difference in circumference). Arm symptoms were reported by 51 (30%) of these 20 (39%) had measured circumference change > 2 cm. Referral to physical therapy was documented for 15% for reduced ROM but at last follow-up noted in 2.3%. The measured lymphedema rate was higher in patients who had mastectomy – 22 v. 11% (p=0.042) and worse with increasing resected axillary dissection volumes (p=0.032), ATV volume (p=0.883), and RT dose inhomgeneity coefficient (p = 0.049). Conclusions: Measured lymphedema rates following AND and 3-DCRT in this study were similar to those reported for AND in randomized studies compared to sentinel node. Careful attention to 3DCRT methods may help optimize lymphedema rates.
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