Room: Exhibit Hall
Purpose: While several ICRU reports recommend planning target volumes (PTVs) in radiation therapy, the frequency of PTV use in routine clinical practice for patients who have undergone breast-conserving surgery is not known. A statewide consortium, focused on quality improvement, evaluated whether or not a PTV was created for the lumpectomy cavity for these patients.
Methods: Baseline data regarding lumpectomy cavity PTV delineation use was acquired from 22 institutions for patients who underwent breast-conserving surgery from 2011 through mid-2016. In 2017, a consortium-wide performance metric was established requiring PTVs for the lumpectomy cavity with the purpose of ensuring adequate target coverage when cardiac dose is considered. The PTV delineation rate was evaluated before and after introduction of the performance metric. Starting in August 2017, the expansion size was captured.
Results: For patients who completed radiotherapy before the intervention (2011- mid-2016; N=6278), 35.0% had a PTV delineated. For patients who completed radiotherapy after the intervention was required (2017; N=1890), this percentage increased to 77.8%. During that time, PTV adoption rates varied by institution (N=22) with 9 institutions delineating a PTV for 90% or more of their patients, 8 between 50-90%, and 5 less than 50% at the end of 2017. The median PTV expansion used by institutions was 1 cm (range 0.1-2 cm).
Conclusion: Introduction of a consortium-wide performance metric was an effective intervention, increasing the PTV delineation rate for the lumpectomy cavity for radiation therapy patients who have undergone breast-conserving surgery. This increase in PTV use will allow the consortium to make target dose homogeneity and coverage recommendations which may aid in weighing clinical tradeoffs between target and heart doses. Future work will investigate the relationship between lumpectomy cavity expansion size as a function of whether or not daily or weekly imaging is used amongst clinics within the consortium.
Funding Support, Disclosures, and Conflict of Interest: Work funded in part by Blue Cross Blue Shield of Michigan and Blue Care Network.