Taisuke Inomata, Presenter: Nothing to Disclose

Yuki Inada, Abstract Co-Author: Nothing to Disclose

Masatsugu Takahashi, Abstract Co-Author: Nothing to Disclose

Toshiaki Tatsumi, Abstract Co-Author: Nothing to Disclose

Yasuo Uesugi, Abstract Co-Author: Nothing to Disclose

Isamu Narabayashi, Abstract Co-Author: Nothing to Disclose

Taiju Shimbo, Abstract Co-Author: Nothing to Disclose

Purpose/Objective: To investigate the dose and volume of the heart that is irradiated with opposed tangential portals for breast conservation therapy in patients with left-sided breast cancer, and clarify how to decrease the irradiated heart dose and volume to reduce the probability of cardiac complication. Materials/Methods: In 157 patients with stage I and stage II breast cancer treated with breast conservation therapy from March 2001 to December 2003, eighty-five left-sided breast cancer patients irradiated with 50 Gy / 25 fractions / 5 weeks were enrolled in this study. Three-dimensional treatment planning system (PrecisePlan version 1.1) was used in all patients. Opposed tangential portals were employed. The maximum depth of the irradiated lung (MDIL) was set at 3.0 cm or less in order to decrease the probabilities of cardiac and pulmonary toxicity. Using a Dose Volume Histogram (DVH) of the heart, v20, v30, v40, and v50 (i.e. vd is defined as an irradiated cardiac volume of d Gy or larger dose) and V20, V30, V40, and V50 (i.e. VD is defined as an irradiated percent cardiac volume of D Gy or larger dose) were calculated. The relationships between the v20-50 / V20-50 and (a) the MDIL (cm), (b) the maximum thickness of the irradiated thoracic wall (cm), (c) a+b (cm), (d) cardiac volume (ml), and (e) Clinical Target Volume (CTV) (ml) were analyzed to evaluate the cardiac complication probabilities. Results: In the correlation coefficients between the v20-50 / V20-50 and the five factors (a-e) described above, v20-40 / V20-40 were significantly correlated with the MDIL (v30, v40, V20-40 p<0.01, v20 p<0.05), with coefficients of v20-0.313, v30-0.405, v40-0.447, V20-0.407, V30-0.435, and V40-0.446. The average v40 / V40 gradually increased from 7.7 ml / 1.4% to 11.2 ml / 2.1%, 16.4 ml / 3.1%, and 27.5 ml / 5.1%, as the MDIL increased from =<1.0 cm to 1.1-2.0 cm, 2.1-2.5 cm, and 2.6-3.0 cm, respectively. In particular, when the MDIL exceeded 2.5 cm, v20-40 and V20-40 increased abruptly. The v50 / V50 was 0.1 ml / <0.1%, 0.7 ml / 0.1%, 1.2 ml / 0.3% and 1.1 ml / 0.2% when the MDIL was =<1.0 cm to 1.1-2.0 cm, 2.1-2.5 cm, and 2.6-3.0 cm. Only a very small cardiac volume was irradiated more than the prescribed dose (50 Gy). There was no significant correlation between the v50 / V50 and MDIL. The v20, v30, and v40 were significantly correlated with the cardiac volume (v20, v30 p<0.01, v40 p<0.05): v20-0.461, v30-0.435, and v40-0.370, whereas the V20-40 and the cardiac volume had no significant correlation. Conclusions: The probability of cardiac complication is very small as long as patients are carefully treated without excessive irradiated cardio-pulmonary dose and volume. In order to minimize the probability of cardiac mortality, the MDIL appears to be a good indicator because v20-40 and V20-40 correlated well with the MDIL, and we could easily measure the MDIL even without a three-dimensional treatment planning system. The MDIL should be set at 2.5 cm or less to efficiently decrease the irradiated cardiac volume and dose.

Inomata, T, Inada, Y, Takahashi, M, Tatsumi, T, Uesugi, Y, Narabayashi, I, Shimbo, T, Cardiac Complication Probabilities after Tangential Irradiation for Breast Conservation Therapy in Patients with Left-sided Breast Cancer.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4420745.html