Breast Cancer

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TU_12_3440 - Radiation effect on late cardiopulmonary toxicity: an analysis comparing DIBH versus prone techniques for breast treatment

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Radiation effect on late cardiopulmonary toxicity: an analysis comparing DIBH versus prone techniques for breast treatment
S. X. Yan1, C. A. Perez1, N. E. Huppert1, C. Hitchen1, I. J. Das1, O. G. Maisonet1, and N. K. Gerber2; 1Department of Radiation Oncology, NYU Langone Health, New York, NY, 2Department of Radiation Oncology, NYU School of Medicine, New York, NY

Purpose/Objective(s): Patients with early stage breast cancer or DCIS have excellent long-term prognosis after lumpectomy and adjuvant whole breast radiation. It is important to reduce radiation-related late cardiac morbidity and secondary lung cancer incidence from adjuvant breast irradiation. Two commonly used treatment techniques; deep inspiration breath hold (DIBH) and prone breast are compared with regard to dosimetry as well as estimated late cardiac morbidity and secondary lung cancer risks using published models.

Materials/Methods: Thirty-four patients with left-sided DCIS or breast cancer who have undergone lumpectomy and required adjuvant whole breast irradiation were enrolled on a prospective trial comparing prone breast with supine DIBH planning (NCI-2017-00219). Patients underwent CT simulation in both positions, and two treatment plans were generated for each patient. Mean cardiac dose and ipsilateral lung doses were calculated. Absolute risk of death from ischemic heart disease (IHD) and risk of at least one acute coronary event (ACE) were estimated from published data by Darby, et al. [NEJM 2013] using individual patient’s age and cardiac risk factors (as per tables S12 and S13). Risk of developing lung cancer based on ipsilateral lung dose was estimated from published data by Taylor, et al. [JCO 2017] (using excess rate ratio of 0.11/Gy and assuming baseline risk as per table S9) using individual patient’s age and smoking history. The difference between radiation-related cardiac and lung cancer mortality between the supine DIBH and prone plans were compared using paired two-tailed T-test.

Results: Median age was 52 (range 38-75) for the entire cohort. Fourteen patients were smokers, and 22 patients possess at least one cardiac risk factor. Mean heart dose was 79.7 cGy and 76.5 cGy (p=0.37), and mean ipsilateral lung dose was 452.7 cGy and 45.2 cGy (p < 0.0001), for supine DIBH and prone plans, respectively. Estimated mean absolute risk of death from IHD by age 80 was 0.1% (range 0.0-0.2%) for both plans (p = 1.0). Estimated mean absolute risk of at least one radiation-related ACE by age 80 was 0.3% (range 0.1-0.6%) for both plans (p = 0.6). Estimated mean lung cancer risk by age 80 was 1.4% (range 0.5-15.4%) from supine DIBH plans and 1.0% (range 0.4-9.8%) from prone plans (p = 0.008). This result translates into an estimated excess lung cancer risk due to radiation by age 80 of 0.5% (range 0.1-6.0%) from supine DIBH plans and 0.0% (range 0.0-0.4%) from prone plans (p = 0.008).

Conclusion: There was no observed difference in mean cardiac dose between supine DIBH and prone techniques, and a low absolute risk of both radiation-related ACE and risk of death from IHD. Whole breast radiation with prone technique results in lower ipsilateral lung dose compared to supine with DIBH. This lower lung dose translates into an absolute decrease of 0.5% in excess lung cancer risk for this cohort of patients receiving whole breast radiation based on published data.

Author Disclosure: S.X. Yan: None. C.A. Perez: None. N.E. Huppert: None. I.J. Das: Honoraria; JASTRO, Japanese Society of Therapeutic Radiation. Speaker's Bureau; JASTRO, Japanese Society of Therapeutic Radiation. Travel Expenses; JASTRO, Japanese Society of Therapeutic Radiation. Committee Member and surveyor; ACR. Associate Editor; Br J Radiology, Medical Physics. examiner; ABR. Committe member and Chair; AAPM. O.G. Maisonet: None. N.K. Gerber: None.

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