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A Patient-Level Data Meta-analysis of the Abscopal Effect.

Authors :: Hatten SJ Jr
Lehrer EJ
Liao J
Sha CM
Trifiletti DM
Siva S
McBride SM
Palma D
Holder SL
Zaorsky NG
Source :: Advances in radiation oncology [Adv Radiat Oncol] 2022 Mar 03; Vol. 7 (3), pp. 100909. Date of Electronic Publication: 2022 Mar 03 (Print Publication: 2022).
Publication Year :: 2022
Abstract: Purpose: The abscopal effect is defined when a form of local therapy causes tumor regression of both the target lesion and any untreated tumors. Herein cases of the abscopal effect were systematically reviewed and a patient-level data analysis was performed for clinical predictors of both duration of response and survival.<br />Methods and Materials: The Population, Intervention, Control, Outcome, Study (PICOS) design approach, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) literature selection process, and Meta-analysis of Observational Studies in Epidemiology (MOOSE) were used to find articles published before September 2019 in MEDLINE/PubMed and Google Scholar. Inclusion criteria were (1) population: patients with reported abscopal response; (2) intervention: documented treatment(s); (3) control: none; (4) outcomes: overall and progression-free survival; and (5) setting: retrospective case reports. Time from treatment until abscopal response and time from abscopal response until progression/death were calculated. Univariate and multivariate analyses were conducted for survival outcomes.<br />Results: Fifty studies (n = 55 patients) were included. Median age was 65 years (interquartile range [IQR], 58-70) and 62% were male. Fifty-four (98%) patients received radiation therapy, 34 (62%) received radiation therapy alone, 5 (9.1%) underwent surgery, 4 (7.3%) received chemotherapy, and 11 (20%) received immunotherapy. Median total dose was 32 Gy (IQR, 25.5-48 Gy) and median dose per fraction was 3 Gy (IQR, 2-7.2). Median time until abscopal response was 4 months (IQR, 1-5; min 0.5, max 24). At 5 years, overall survival was 63% and distant progression-free survival was 45%. No variables had statistical significance in predicting duration of response or survival.<br />Conclusions: Almost all reported cases of the abscopal response are after radiation therapy; however, there are no known predictors of duration of response or survival in this population.<br /> (© 2022 The Authors.)