Cardiac and lung complication probabilities after breast cancer irradiation

Purpose: To assess for locoregional irradiation of breast cancer patients, the dependence of cardiac (cardiac mortality) and lung (radiation pneumonit is) complications on treatment technique and individual patient anatomy. Materials and methods: Three-dimensional treatment planning was performed f or 30 patients with left-sided breast cancer and various breast sizes. Two locoregional techniques (Techniques A and B) and a tangential field techniq ue, including only the breast in the target volume, were planned and evalua ted for each patient. In both locoregional techniques tangential photon fie lds were used to irradiate the breast. The internal mammary (IM)-medial sup raclavicular (MS) lymph nodes were treated with an anterior mixed electron/ photon held (Technique A) or with an obliquely incident mixed electron/phot on IM field and an anterior electron/photon MS field (Technique B). The opt imal IM and MS electron field dimensions and energies were chosen on the ba sis of the IM-MS lymph node target volume as delineated on CT-slices. The p osition of the tangential fields was adapted to match the IM-MS fields. Dos e-volume histograms (DVHs) and normal tissue complication probabilities (NT CPs) for the heart and lung were compared for the three techniques. In the beam's eye View of the medial tangential fields the maximum distance of the heart contour to the posterior field border was measured; this value was s cored as the Maximum Heart Distance. Results: The lymph node target volume receiving more than 85% of the prescr ibed dose was on average 99% for both locoregional irradiation techniques, The breast PTV receiving more than 95% of the prescribed dose was generally smaller using Technique A (mean: 90%, range: 69-99%) than using Technique B (mean: 98%, range: 82-100%) or for the tangential field technique (mean: 98%, range: 91-100%). NTCP values for excess cardiac mortality due to acute myocardial ischemia Varied considerably between patients, with minimum and maximum values of 0.1 and 7.5% (Technique A), 0.1 and 5.8% (Technique B) a nd 0.0 and 6.1% (tangential tech.). The NTCP values were on average signifi cantly higher (P < 0.001) by 1.7% (Technique A) and 1.0% (Technique B) when locoregional breast irradiation was given, compared with irradiation of th e left breast only. The NTCP values for the tangential field technique coul d be estimated using the Maximum Heart Distance. NTCP values for radiation pneumonitis were very low for all techniques; between 0.0 and 1.0%. Conclusions: Technique B results in a good coverage of the breast and locor egional lymph nodes, while Technique A sometimes results in an underdosage of part of the target volume. Both techniques result in a higher probabilit y of heart complications compared with tangential irradiation of the breast only. irradiation toxicity for the lung is low in all techniques. The Maxi mum Heart Distance is a simple and useful parameter to estimate the NTCP va lues for cardiac mortality for tangential breast irradiation. (C) 2000 Else vier Science Ireland Ltd. All rights reserved.