Long-term risks of secondary cancer for various whole and partial breast irradiation techniques

Publication date: Available online 18 June 2018
Source:Radiotherapy and Oncology
Author(s): Nienke Hoekstra, Emmanuelle Fleury, Tomas Rodrigo Merino Lara, Peter van der Baan, Andy Bahnerth, Gerson Struik, Mischa Hoogeman, Jean-Philippe Pignol
IntroductionFor early stage breast cancer patients, non-breast cancer mortality including secondary cancers and cardiac events can overshadow the benefit of adjuvant radiotherapy. This study evaluates the excess risk of secondary cancer for various breast radiotherapy techniques including accelerated partial breast irradiation (APBI).MethodsSecondary cancers Lifetime Attributable Risks (LAR) were calculated using a modified BEIR-VII formalism to account for the specific survival of breast cancer patients. Those survivals were extracted from the SEER database. Doses scattered to various organs were measured into a Rando phantom with custom-made breast phantoms. Treatments delivered typical doses of brachytherapy APBI (34 Gy in 10 fractions), external beam APBI (38.5 Gy in 10 fractions) using 3D-conformal, Cyberknife stereotactic (CK), or VMAT, as well as whole breast irradiation (WBI) delivering 42.5 Gy in 16 fractions.ResultsWBI resulted in the highest total LAR, with 4.3% excess risk of secondary cancer for a patient treated at age 50 years. Lung cancers accounted for 75–97% of secondary malignancies. For a typical early stage patient irradiated at 50, the excess risks of secondary lung cancer were 1.1% for multicatheter HDR, between 2.2% and 2.5% for 3D-CRT or CK, 3.5% for VMAT APBI, and 3.8% for WBI.ConclusionsAPBI reduces the risk of secondary cancer 2–4 fold compared to WBI. These techniques are well suited for long-living early stage breast cancer patients. HDR brachytherapy and 3D-conformal APBI achieve mean lung doses between 1 and 1.5 Gy, which could serve as reference.



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