Introduction: Adherence to clinical practice guidelines (CPGs) has long been a challenge due to a lack of knowledge about CPGs and the fact that CPGs may not be practical in the context of a particular patient's situation. Poor adherence to the 2011 American Society for Radiation Oncology (ASTRO) evidence-based guideline on whole breast irradiation has been reported, especially for hypofractionated whole breast radiotherapy (HBRT). In 2018, updated ASTRO guidelines were published. We utilized theMednet, an online Q&A platform of over 3,600 US community and academic radiation oncologists (ROs), to assess current views regarding whole breast RT and evaluate relationships between the the strength of guideline recommendation statements and ROs views on treatment choices.

Methods: We identified 11 questions previously asked by community ROs on theMednet that were not addressed in the 2011 ASTRO whole breast irradiation guideline. Questions were originally asked between 10/27/2014 and 5/2/2017. These questions were sent to a senior author of the 2018 guidelines to post an updated response on theMednet, citing the guidelines and degree of consensus. A link to view the full guidelines was provided. New answers citing the guidelines were disseminated in 3 biweekly newsletters between 3/16/2018 and 5/1/2018, along with polls to survey radiation oncologists participating in theMednet.

Results: A total of 792 ROs responded to polls, of whom 523 were community ROs, 129 were academic ROs, and 93 were residents. Of the 11 questions, 10 pertained to WBRT and 1 pertained to conventional dose fractionation. For each question, the answer choice receiving the majority of the votes aligned with the 2018 guideline. Of the 5 questions which referenced a conditional recommendation in the 2018 guideline, the majority vote ranged from 54% to 87%; whereas, of the 6 questions which referenced a strong recommendation in the 2018 guideline, the majority vote from 62% to 97%. The strongest consensus was for HBRT to be used regardless of histology (97%), followed by molecular subtype (90%), grade (89%), and concurrent use of trastuzumab (87%). The least consensus was for age at which HBRT should be offered, with only 54% of respondents agreeing with the guideline consensus that HBRT should be offered regardless of age. When comparing academic and community ROs, 73% of academic ROs do not specify an age threshold for offering HBRT, compared to 47% of community ROs (P=0.0240). Regarding boost dose-fractionation, 83% of academic ROs prefer a 10Gy in 4 fractions while 54% of community ROs prefer 10 Gy in 5 fractions and 41% prefer 10Gy in 4 fractions (P=0.1495). Responses were similar between academic and community ROs for all other questions.

Conclusion: Utilizing an online platform, theMednet, we were able to assess current views of management of whole breast radiation therapy among participating ROs. The majority of ROs agree with the major recommendations from this guideline, with practice variation greater in areas with weaker underlying evidence.

Citation Format: Burt L, Haffty BG, Smith B, Housri N. Radiation oncologists' views on breast radiation therapy guidelines: Utilizing an online Q&A platform to assess current views on whole breast radiation therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-16-05.