Tatiana Conrad

Active breathing control for patients receiving mediastinal radiation therapy for lymphoma: Impact on normal tissue dose

PURPOSE Active breathing control (ABC) is emerging as a tool to reduce heart and lung dose for lymphoma patients receiving mediastinal radiation therapy (RT). The objective of this study was to report our early institutional experience with this technique, with emphasis on quantifying the changes in normal tissue dose and exploring factors that could be used to select patients with the greatest benefit. METHODS AND MATERIALS Patients receiving mediastinal involved-field RT (IFRT) for lymphoma were eligible. The ABC was performed using a moderate deep-inspiration breath-hold (mDIBH) technique. All patients were replanned with free-breathing (FB) computed tomographic data sets and comparisons of lung, cardiac, and female breast tissue doses were made between mDIBH and FB plans. Logistic regression models were used to identify factors associated with improvement in mean lung and heart dose with mDIBH. RESULTS Forty-seven patients were analyzed; the majority (87.2%) had Hodgkin lymphoma. Median prescribed dose was 30 Gy (range, 20-36 Gy), with 78.7% of cases being treated with parallel-opposed beams. The use of mDIBH significantly improved average mean lung dose (FB: 11.0 Gy; mDIBH: 9.5 Gy; P < .0001), lung V20 (28% vs 22%; P < .0001), and mean heart dose (14.3 Gy vs 11.8 Gy; P = .003), but increased the mean breast dose (FB: 3.0 Gy; mDIBH 3.6 Gy; P = .0005). The magnitude of diaphragmatic excursion on the inhale scan was significantly associated with dosimetric improvement in both heart and lung dose with mDIBH. CONCLUSIONS Mediastinal IFRT for lymphoma delivered with mDIBH can significantly reduce lung and heart dose compared with FB, although not for all patients, and may increase breast dose in females. Its implementation is achievable in both adult and pediatric populations. Further work is necessary to better predict which patients benefit from this technique.

Sites of gastric cancer recurrence after adjuvant chemoradiotherapy.

68 Background: Since the Intergroup 0116 study in 2000, adjuvant post-operative chemoradiotherapy (CRT) has been offered routinely to similar patients with resected gastric cancer at Princess Margaret Hospital (PMH) using CT-planned and 3D conformal/intensity modulated radiotherapy (RT). The objective of this study was to analyze patterns of recurrence with respect to RT treatment volumes. METHODS Date and site (local, locoregional or distant) of first recurrence data was obtained from chart review for all patients treated at PMH with adjuvant CRT for resected gastric adenocarcinoma (Jan. 1, 2000-Nov. 30, 2009). Patients whose recurrences were limited to local (gastric remnant, duodenal margin, gastric bed recurrence) and/or regional sites (regional lymph node recurrence) were selected for analysis. When available, diagnostic imaging of recurrence site was registered to the original planning RT dataset. The center of mass for each recurrence was identified as a point and its location categorized according to the isodose encompassing it; in-field (≥ 90%), marginal (50%-89%), and out-of-field (< 50%). RESULTS Three-year OS, and RFS were 66% (95% CI: 58-73) and 58% (50-60), respectively. Of 203 patients treated, 75 recurrences were identified (Table). Of the 13 local/locoregional recurrences, 4 were in-field, 1 marginal, 1 could not be registered due to change in body habitus, and 7 did not have an available original dataset. CONCLUSIONS Rates of isolated local and/or regional recurrence in this study were low. This represents a change in the pattern seen with surgery alone suggesting the addition of CRT results in decreased isolated local and/or regional recurrence. Of the small number of local and/or regional recurrences available for analysis, all were in-field or marginal. Further studies involving a larger cohort of patients might allow for more meaningful analysis of trends in recurrence site with evolving RT techniques. [Table: see text] No significant financial relationships to disclose.