Changing Practice Patterns in the Radiation Treatment Delivery for Locally Advanced Lung Cancer: Results from a Statewide Consortium

Abstract

In 2014, the RTOG 0617 trial defined the standard radiation therapy (RT) dose as 60 Gy with concurrent chemotherapy in locally advanced non-small cell lung cancer (LA-NSCLC) patients. Further analyses of the study showed a decrease in grade 3 pneumonitis with static intensity modulated radiation therapy (sIMRT). Radiation treatment techniques used in routine clinical practice have evolved from 3D conformal radiation therapy (3DCRT) to sIMRT and more recently to rotational IMRT (rIMRT). However, the uptake of lower lung tumor RT dose recommendations and RT treatment techniques used in the “real world” setting is not known. The purpose of this study was to evaluate patterns of practice of both radiation dose and type of radiation technique used in a statewide radiation oncology consortium. From 2012 to 2018, 2741 patients with lung cancer treated with curative intent RT at 24 institutions participating in a statewide Radiation Oncology Quality Consortium were enrolled. Patients with small cell lung cancer, previous surgical resection, and patients who did not complete treatment were excluded. Furthermore, for RT dose analyses, outliers of RT doses (<45 Gy and >100 Gy) were excluded. Patients lacking DICOM information regarding treatment plans were excluded for the RT technique analyses. Changes in prescription doses and treatment techniques over time were evaluated. Trends over time in academic (n=4) vs. non-academic centers (n=20) were also analyzed. Academic centers were defined as those with a medical residency training program. Sample t-tests were used to compare means. 1134 patients were analyzed for RT dose analysis, while 1087 patients were evaluated for the RT treatment technique. The mean prescription RT dose delivered to tumor decreased from 63 Gy to 60 Gy (p<0.001) over the 6-year time period. In the earlier years of the data collection (2012-2013), >50% of the cases were treated with 3DCRT and rIMRT was used in ≤5%. However, by 2018, the rate of rIMRT increased to 56.9% (p<0.0001). See Table below. Similar practice patterns were seen in academic and non-academic centers for both RT dose and treatment technique analyses. In this large prospective “real world” study from a statewide consortium of practicing radiation oncologists, prescription mean RT dose used to treat LA-NSCLC has decreased to 60 Gy as per evidence-based guidelines. The primary treatment technique of delivering RT in LA-NSCLC has also changed in this interval. More than half of LA-NSCLC patients are now receiving rIMRT. The clinical implications of potential increases in low dose volumes (e.g., Lung and Heart V5) resulting from rIMRT will have to be evaluated going forward, especially in the changing systemic therapy paradigm that includes immunotherapy.Abstract 3120; Table 1Year3DCRTsIMRTrIMRT201263.5%34.6%1.9%201355.1%40.4%4.5%201444.8%38.1%17.2%201540.2%33.1%26.7%201619.0%31.4%49.6%201721.9%25.1%53%201821.8%21.3%56.9% Open table in a new tab