K. Zhang1, J. Patel2, C. D. Fuller3, J. S. Remick2, and T. Y. Eng2; 1Emory University School of Medicine, Atlanta, GA, 2Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, 3Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Overall survival (OS) is amongst the most common metric to delineate patient outcomes with or without therapy. However, OS may be less predictive for patients who have received the appropriate therapy following diagnosis. Conditional survival (CS) is defined as the probability of surviving an additional number of years given a patient who has already survived a certain amount of time following diagnosis and adjusting for fluctuating hazard rates over a specified period of time. CS may help tailor post-therapy surveillance, guiding clinicians in optimizing resources, and providing survivors with personalized predictive data. Prior literature has examined and validated CS models for various oncologic diseases. In this study, we report CS for gynecologic malignancies using Surveillance, Epidemiology, and End Results (SEER) database for patients who have received treatment with radiation therapy. Materials/
Methods: Utilizing the SEER 22 database and SEER*Stat 8.4.3, gynecologic malignancies (including subgroup cervix uteri, corpus uteri, uterus NOS, vagina, vulva) were identified between 2000-2020. Additional inclusion criteria included “local” or “regional” disease and records containing treatment with external beam radiation therapy (EBRT), brachytherapy, or both. Cases with postmortem diagnosis, lost to follow up, or dead due to other causes were excluded from further analysis. SEER 22 has a “months from diagnosis to treatment” threshold of 24 months. CS for years 1-5 after 24 months from diagnosis were calculated for the included cohort. Results: There were 106,961 patients in the initial cohort. Of these, 69,556 (65%) patients received radiation within the 24-month threshold (remainder unknown). This was further subdivided into 29,184 (42%) patients who received EBRT only, 20,870 (30%) who received brachytherapy only, and 19,502 (28.0%) who received combined EBRT and brachytherapy. CS was therefore calculated following 2 yrs from diagnosis to best capture every treated patient. In the combination therapy group, 1yr CS for cervix, corpus uteri, uterus NOS, vagina, and vulva were: 92.7%, 91.2%, 89.3%, 92.9%, and 92.6%, respectively. CS at 5yrs (up to 7 years from diagnosis) was 80.9%, 82.5%, 64.2%, 83.2%, and 83.6%. respectively. In the brachytherapy group, 5yr CS was 82.5%, 91.4%, 86.6%, 84.6%, and 54.5%, respectively. Finally, in the EBRT group 5yr CS was 80.3%, 82.3%, 66.7%, 73.4%, and 74.8% respectively. Conclusion: Conditional survival is an effective method to prognosticate patients over time. In our cohort of patients with gynecologic malignancies treated with radiation the overall trends for 5yr CS following an initial 2 yrs of survival within a likely treatment window were similar across any treatment modality. These findings may help elucidate statistics for survivorship care and may help develop evidence-based policies.
