BackgroundWe developed, applied, and prospectively evaluated a novel deep-inspiration breath-hold (DIBH) screening and delivery technique to optimize cardiac sparing in left-breast radiotherapy (RT) at our clinic. The impact of set-up and dose variables upon organs at risk (OAR) dose in DIBH RT was investigated.Methods and materialsAll patients with left-breast cancer referred between 2011 and 2014 – of all disease stages, set-up variations, and dose prescriptions – were included. Radiographers used simple screening criteria at CT simulation, to systematically assess patients for obvious DIBH benefit and capability. Selected patients received forward-planned intensity-modulated RT (IMRT) based on a DIBH CT scan. A 3D-surface monitoring system with visual feedback assured reproducible DIBH positioning during gated radiation delivery. Patient, target set-up, and OAR dose information were collected at treatment.ResultsOf 272 patients who were screened, 4 withdrew, 56 showed no obvious advantage, and 56 showed benefit but had suitability issues; 156 patients were selected and successfully completed DIBH treatment. The technique was compatible with complex set-up and optimal target coverage was maintained. Comparison of free-breathing (FB) and DIBH treatment plans in the first five patients enrolled confirmed DIBH reduced heart radiation by ~80% (p = 0.032). Low OAR doses were achieved overall: the mean (95% confidence interval [CI]) heart dose was 1.17 (1.12–1.22) Gy, and the mean ipsilateral lung dose was 5.26 (5.01–5.52) Gy. Patients who underwent a standard radiation schedule (40 Gy/15#) after breast-conserving surgery had the lowest OAR doses: post-mastectomy treatment, simultaneous supraclavicular (SCV) node coverage, and alternative dose schedule (50 Gy/25#) were interrelated variables associated with increased OAR risk and compromised ipsilateral lung dose constraints.ConclusionThe DIBH technique was successfully implemented and resulted in optimally low heart radiation. All patients who demonstrate sufficient DIBH technique at planning CT are now offered DIBH RT at our clinic. Patients with more advanced disease, particularly those with additional pulmonary risk factors, warrant additional focus to improve lung sparing.
A right-sided breast cancer patient (stage T1N0M0) was referred for post-surgical radiotherapy to minimize risk of local tumour recurrence. During the CT simulation and intensity-modulated radiotherapy planning process undertaken in free breathing, it was apparent that an unusually large volume of normal liver tissue (134 cc) was in the high-dose region of the tangential radiation field. This raised concern for risk of liver side effects and was considered suboptimal for this excellent prognosis patient. A deep inspiration breath-hold (DIBH) technique using three-dimensional (3D) surface monitoring—primarily developed and applied in left breast cancer to displace cardiac tissue from the target field—was investigated to determine potential benefit to optimize radiotherapy delivery. Resimulation of DIBH resulted in considerable displacement of the liver, reducing the volume of liver tissue in the target field by 63% (to 50 cc) and the mean liver dose by 46% (to 2.6 Gy). As the patient was deemed suitable for the DIBH technique, treatment was delivered according to the DIBH plan. A total of 40.05 Gy in 15 fractions was successfully delivered in the DIBH position using a technique that incorporated 3D body surface imaging with automated radiation beam hold-off when out of tolerance. Additional advantages were optimal set up without extensive immobilization and the elimination of respiratory motion. Acute mild skin erythema was the only side effect experienced—no liver sequalae were experienced by the patient up to 6 months after treatment. DIBH treatment may improve liver sparing in other similar right breast cancer patients.
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