Variability of Current Clinical Practices for Locally Advanced Cervical Cancer through Assessment of Contouring, Prescription, and IMRT/VMAT Planning Abilities

There is a high prevalence of cervical cancer in Latin America and increasing interest in advanced radiotherapy techniques. Despite technological advancements and efforts to standardize radiotherapy management of cervical cancer, variability exists among providers in Latin America and globally. In an effort to increase the knowledge of evidence-based practices globally, the first Latin American Cooperative Study (LACOS-1) sought to understand the variability of current clinical practices for locally advanced cervical cancer through assessment of contouring, prescription, and treatment planning abilities. A trilingual (English, Spanish, and Portuguese) de-identified simulated case presentation of cervical cancer was provided to clinic coordinators. Participants included radiation oncologists, residents, medical physicists, and dosimetrists from 12 centers across 8 Ibaeroamerican countries. Each center was tasked with planning pelvic external beam radiotherapy (EBRT) using either intensity modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) according to their current individual practices. Structure labels without prescriptions but with specific target definitions were provided. Additional directives were left to the discretion of clinics. Contours and plans were developed using each institution’s planning software and analyzed with ProKnow DS. Descriptive statistics were conducted. Forty contours and plans were submitted and 38 were available for analysis. Dose covering 95% of PTV ranged from 41.7 to 50.6Gy (mean 47.5, SD 2.5) and maximum point dose (Dmax) to the PTV ranged from 47.7 to 74.9Gy (mean 55.3, SD 5.2). Volume (cc) of the GTV from 25 (66%) contours ranged from 22 to 190cc (mean 88.6, SD 42.0). Volume (cc) of PTV ranged from 359 to 1385cc (mean 1067.0, SD 236.9). Conformality index of PTV at the 95% prescribed dose ranged from 1.0 to 2.9 (mean 1.3, SD 0.4). Representative of OAR DVH, the volume (%) of the bladder covered by 40Gy ranged from 22.8 to 100% (mean 63.4, SD 19.3). Dmax of the bowel from 16 (42%) participants with bowel contours ranged from 46.8 to 58.6 (mean 51.8, SD 3.7). Eleven participants (29%) from 7 centers prescribed an EBRT parametrial boost. Eleven participants (29%) utilized IMRT, while 27 (71%) used VMAT. Of these 27 individuals, 13 (48%) planned with 2 arcs, 9 (33%) with 1 arc, 3 (11%) with 5 arcs, and 2 (8%) with 3 arcs. This descriptive analysis illustrates the existing variability in representative cervical treatment plans in Latin America. The differences in target coverage and OAR constraints could correlate with clinical outcomes. Further understanding of the current clinical practices in Latin America is needed to inform interventions such as tele-education and remote treatment planning review. Future analysis of ongoing treatment plans with standardized instructions will further characterize the quality of care and potential training opportunities across countries.