MDNews - Cleveland-Akron-Canton

+++++++++++++++++++++++++++++++++++ + + +++++++++++++++++++++++++++++++++++ ADVANCES IN RADIOTHERAPY +++ +++ Cardio-Sparing f Radiation Therapy By Janice Lyons, MD M ANY WOMEN WHO are diag- nosed with breast cancer undergo radiation therapy as part of their treatment plan. Treatment volumes include the breast after breast conserving surgery or the chest wall following mastectomy, with or without regional lymph node irradiation. Recent studies suggest that not only is there a local control advantage to adjuvant radiation, but also potentially a survival advantage. There is a suggestion that women with node positive breast cancer may benefit from comprehensive nodal irradiation, which includes larger volumes of normal tissues including the heart. Initial studies looking at the benefit of adjuvant radiation suggested a cancer specific survival advantage to the addition of radiation, but no advantage in overall survival. In a meta-analysis published in the early 1990's, Cuzick et al suggested that the reduced risk of breast cancer death among women receiving adjuvant radiation was offset by an increased risk of cardiac-related death years later. It has been difficult to quantify the effects of radiation on the heart for many reasons. First, up until about 10-15 years ago, CT scanning was not routinely used in radiation planning so cardiac dose parameters were not available. Another confounding factor is that it often takes many years for the damage from radiation to be realized. A study of 4,456 women treated between 1954 and 1983 found a 1.76-fold higher risk of cardiac disease and a 1.33-fold high risk of dying from vascular disease among women treated for left-sided breast cancer as compared or Breast Cancer to those with right-sided breast cancer. Although the radiation techniques used for these studies are now outdated and no CT data exists to confirm the radiation doses to the patients' hearts, other, more recent studies confirm that the risk of radiation-related cardiac damage still exists, especially in cases of left-sided breast cancer. In a study published in 2008, Taylor and colleagues evaluated the radiation plans of 50 patients with left-sided breast cancer and 5 with right-sided breast cancer. Although the radiation dose to all cardiac structures was 1.2-2 Gy for right- sided patients, in half of those treated for left-sided cancer, part of the heart received a dose higher than 20 Gy. This higher dose has been shown to raise the risk of coronary artery stenosis in the mid and distal left anterior descending artery (LAD), a common site of atherosclerosis leading to heart attack. Newer techniques are evolving that may offer better protection of the heart during radiation treatment. One prom- ising strategy for reducing cardiac radiation dose during breast cancer treatment is a breath-holding technique called deep-inspiration using an active breathing control (ABC) device. By moving the heart down and away from the chest wall during treatment, deep- inspiration appears to be able to be able to offer some protection. A retrospective review from Duke University comparing 20 CT treat- ment plans performed using either the ABC-assisted deep-breathing method or free-breathing showed a significant difference in cardiac dose. Investigators 26 | Cleveland-Akron-Canton MD NEWS n MDNEWS.COM n MARCH-APRIL 2012 reported a mean radiation dose to the heart of 17.7 Gy (and a maximum of 45.6 Gy) without the technique, but just 1.75 Gy (max 2.96 Gy) with it. Studies are ongoing to better deter- mine tolerance doses for the heart and coronary arteries. Until formal guidelines can be established, radiation oncologists should make efforts to protect the heart during radiation treatment for left-sided breast cancer to reduce the risk of long- term cardiac damage. Dr. Janice Lyons is a radiation oncologist and director of Breast Cancer Services at University Hospitals Case Medical Center, where she is also director of the Residency Program. ■ References Cuzick J. et al, "Cause-specific mortality in long-term survivors of breast cancer who participated in trials of radiotherapy", J. Clin. Oncol. 12, 447-453 (1994). Boullion K. et al, "Long-term cardiovas- cular mortality after radiotherapy for breast cancer", J. Am. Coll. Cardiol. 57(4), 445-452 (2011). Taylor C.W. et al, "Cardiac exposures in breast cancer radiotherapy: 1950s-1990s. Int. J. Radiat. Oncol. Biol. Phys. 69(5), 1484-1495 (2007) Taylor C.W. et al, "Cardiac dose from tangential breast cancer radiotherapy in the year 2006", Int. J. Radiat. Oncol. Biol. Phys. 72(2), 501-507 (2008). Zagar T.M. et al, "Dosimetric comparison of radiotherapy for left-sided breast can- cer: breath-hold versus free-breathin". Presented at: The San Antonio Breast Cancer Symposium, San Antonio, TX, 6-10 December 2010.

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