Elizabeth S. Evans

Prospective assessment of radiotherapy‐associated cardiac toxicity in breast cancer patients: Analysis of data 3 to 6 years after treatment

Radiation therapy (RT) to the left breast/chest wall has been linked with cardiac dysfunction. Previously, the authors identified cardiac perfusion defects in approximately 50% to 60% of patients 0.5 to 2 years post‐RT. In the current study, they assessed the persistence of these defects 3 to 6 years post‐RT.

Radiation-Induced Reductions in Regional Lung Perfusion: 0.1–12 Year Data From a Prospective Clinical Study

PURPOSE To assess the time and regional dependence of radiation therapy (RT)-induced reductions in regional lung perfusion 0.1-12 years post-RT, as measured by single photon emission computed tomography (SPECT) lung perfusion. MATERIALS/METHODS Between 1991 and 2005, 123 evaluable patients receiving RT for tumors in/around the thorax underwent SPECT lung perfusion scans before and serially post-RT (0.1-12 years). Registration of pre- and post-RT SPECT images with the treatment planning computed tomography, and hence the three-dimensional RT dose distribution, allowed changes in regional SPECT-defined perfusion to be related to regional RT dose. Post-RT follow-up scans were evaluated at multiple time points to determine the time course of RT-induced regional perfusion changes. Population dose response curves (DRC) for all patients at different time points, different regions, and subvolumes (e.g., whole lungs, cranial/caudal, ipsilateral/contralateral) were generated by combining data from multiple patients at similar follow-up times. Each DRC was fit to a linear model, and differences statistically analyzed. RESULTS In the overall groups, dose-dependent reductions in perfusion were seen at each time post-RT. The slope of the DRC increased over time up to 18 months post-RT, and plateaued thereafter. Regional differences in DRCs were only observed between the ipsilateral and contralateral lungs, and appeared due to tumor-associated changes in regional perfusion. CONCLUSIONS Thoracic RT causes dose-dependent reductions in regional lung perfusion that progress up to approximately 18 months post-RT and persists thereafter. Tumor shrinkage appears to confound the observed dose-response relations. There appears to be similar dose response for healthy parts of the lungs at different locations.

Is there an increased risk of local recurrence under the heart block in patients with left-sided breast cancer?

UNLABELLED Tangential radiotherapy for left-sided breast cancer may be cardiotoxic. Shaping the field with a heart block reduces cardiac exposure but may under-dose the breast and/or chest wall. We compared the incidence and location of local recurrences in patients irradiated with and without a heart block. METHODS AND MATERIALS Between 1994 and 1998, 180 patients irradiated to the left breast and/or chest wall were retrospectively reviewed. The local recurrence rates in patients treated with and without a heart block were compared using a 2-tailed Fisher exact test. An in-depth dosimetric analysis was performed in 23 patients to assess the percentage of breast tissue under-dosed by inclusion of the heart block. RESULTS Overall, the local recurrence rates in patients with or without a heart block were similar. In postlumpectomy patients with inferiorly located tumors, the rates of local recurrence with and without a heart block were 2 of 6 patients versus 0 of 19 patients, respectively. In the dosimetric analysis, the average percentage of breast tissue under-dosed by the inclusion of a heart block was 2.8% (range, 0%-11%). DISCUSSION A heart block is a reasonable method to limit cardiac dose but should be used cautiously following a lumpectomy in patients with inferiorly located tumors. Additional study with larger numbers of patients is warranted.

SU‐FF‐J‐131: Is There a Relationship Between Body Mass Index, Treatment Set‐Up Errors, and the Development of Myocardial Perfusion Defects Following Radiation Therapy for Left‐Sided Breast Cancer?

Purpose: To assess whether body mass index (BMI) affects the rate of “deep” set‐up errors (i.e. those that increase the volume of heart irradiated), resulting in an increased risk of RT‐induced myocardial perfusion defects (PD) 6–60 months post‐RT. Materials and Methods: For 87 patients receiving RT for left‐sided breast cancer,treatment set‐up accuracy was determined by measuring the height of the lung shadow seen at the level of the central axis on simulation and serial medial tangent portal films. SPECT nuclear medicine scans were performed serially pre‐ and post‐RT to assess for cardiac PD. The interaction among BMI, set‐up error frequency, and the rate of PD was compared using a 1‐tailed Fishers Exact Test. Results: The rates of deep set‐up deviations were 9/32 vs. 24/51 in patients with BMI 0% but ⩽1% LV in the field (i.e. patients who are generally predicted to be at very low risk for RT‐induced cardiac dysfunction). The rates of PD in these patients with deep vs. “shallow” set‐up errors (i.e. those that decrease the volume of heart irradiated) were 5/6 vs. 3/10 (p=0.059) (Fig 2). Conclusions: Patients with BMI⩾25 kg/m2 tend to have a higher incidence of deep set‐up errors, causing more heart to be irradiated than intended. In patients with very small volumes of heart in the RT field, those with deep set‐up errors are more likely to have PD post‐RT. Accurate patient set‐up on the treatment machine is critical to minimize the risk of RT‐induced cardiac injury, particularly in overweight and obese patients. Supported by grants 17‐98‐1‐8071 and BC010663 from the DOD.