OC-0398: HDR brachytherapy boost for ductal carcinoma in situ of the breast with close or positive margins
F. Gines, María José Santos, J.L. Guinot, Araceli Moreno, J. Fernandez, Marina Peña, C. Bosó, M.I. Tortajada, L. Arribas · Radiotherapy and Oncology · 2018
Purpose or ObjectiveIn longitudinal analysis of late side effects after radiotherapy, different statistical methods can be applied to summarize the outcome.Crude incidence rates, actuarial estimates and prevalence rates are well known approaches.These methods characterize specific aspects of the time-evolution of morbidity.None of these metrics capture the duration of a given symptom at the level of an individual patient.A novel approach based on a stepwise selection of patients with late, persistent, substantial and treatment-related symptoms (LAPERS) is introduced to identify patients with substantial and persisting symptoms, which are likely treatment-related. Material and MethodsPatient-reported symptoms (EORTC-QLQ) were analyzed for patients enrolled in the prospective, observational, and longitudinal study on MRI image-guided, adaptive brachytherapy in locally advanced cervical cancer (EMBRACE study).Patients with at least 3 late follow up assessments (6 months and ongoing) and information at baseline and early morbidity were selected for analysis.A LAPERS event for an individual patient was defined if the median grading over late follow up observations of a given symptom was at least "Quite a bit" or "Very much" (substantial symptoms).Baseline morbidity was taken into account by requiring the median to be worse than the minimum of baseline or early assessment scoring.The LAPERS approach was applied in four relevant patientreported symptoms on urinary and bowel function. ResultsWithin the EMBRACE cohort, 581 out of 1416 patients (41%) fulfilled the selection criteria for this analysis.Median follow-up was 36 months (IQR 24-54).Table 1 presents the outcome, based on the different methods of reporting.The crude incidence is nearly twice as high as the highest prevalence rate.The actuarial probabilities for substantial symptoms, based on the estimation for remaining patients at risk, are around 4-5% higher than crude incidence.The proportion of patients with LAPERS events is 4-5 times lower than crude incidence, indicating that in some cases symptoms are persistent.Conclusion Many symptoms after radiotherapy are fluctuating, transient or successfully treated.Incidence methods capture the (first) occurrence of an event and cannot discriminate whether patients suffer from chronic or transient treatment-related morbidity.The novel LAPERS metric for analyzing longitudinal symptoms aims to identify patients with late, persistent, substantial and treatment-related symptoms.Expectedly, the proportion of LAPERS events is substantially lower than the wellestablished crude incidence, prevalence rates and actuarial estimates in cervix cancer patients after radiochemotherapy.The LAPERS estimates will be further tested and validated within the EMBRACE study and beyond, as it seems to be sensitive in terms of quantifying the proportion of patients with persistent, clinically relevant symptom burden.