Comparative Analysis of the Benefit of Radiation Therapy for Oligometastasis, Oligorecurrence, and Oligoprogression

Abstract

Randomized Phase II trials show that local consolidative radiation therapy (RT) after systemic therapy (ST) improves progression-free survival (PFS) and overall survival (OS) in select patients with oligometastatic disease. Our hypothesis is that RT will have a similar benefit in related situations like oligorecurrence or oligoprogression. The charts of all patients treated for oligometastatic, oligorecurrent, or oligoprogressive cancer at our institution from 2013 – 2019 were reviewed. Subgroups of patients were categorized according to RT indication, and the use of ST in relation to the RT. The Kaplan-Meier method was used to determine PFS from the completion of RT. This analysis included 134 RT courses among 80 eligible patients. The most common primary tumor sites were lung (51%) and breast (14%). The most common RT treatment technique was SBRT (80.6%), and the median BED10 of all RT regimens was 88 Gy (interquartile range (IQR) 59 – 113 Gy). At a median follow-up of 14 (IQR 7 – 24) months, the median PFS was 7.0 (IQR 4.7 – 9.3) months. Table 1 shows PFS for each subgroup of patients assessed. The majority of patients with metastatic cancer experienced an extended progression-free interval after RT to limited sites of active disease, though with significant variations in PFS within each subgroup. Further assessment of risk factors for early progression after RT will be critical to optimizing patient selection for RT in this setting.Abstract 3320; Table 1RT Indicationn (%)Median PFS (95% CI)Relationship of ST to RTn (%)Median PFS (95% CI)(1) De novo oligometastastic, treated with up-front RT9 (7%)7.0 (0.0 – 17.3)(1) Off ST >12 weeks prior to RT--> use of further ST delayed until progression46 (34%)5.0 (2.9 – 7.1)(2a) De novo oligometastastic without progression after a single line of ST prior to RT11 (8%)7.0 (4.5 – 9.5)(2) Off ST >12 weeks prior to RT--> new ST started before any evidence of progression12 (9%)13.0 (0.0 – 26.2)(2b) De novo oligometastastic with limited residual or progressive disease after multiple lines ST prior to RT12 (9%)2.0 (0.0 – 9.3)(3) On ST prior to RT--> same ST continued after RT32 (24%)5.0 (0.9 – 9.1)(3) De novo widely metastatic with induced oligometastatic state after ST10 (8%)4.0 (1.0 – 7.0)(4) On ST prior to RT--> new ST started after RT before any evidence of progression7 (5%)8.0 (3.7 – 12.3)(4) Oligorecurrent after prior curative-intent therapy, treated with up-front RT29 (22%)10.0 (7.6 – 12.4)(5) On ST prior to RT--> use of further ST delayed until progression29 (22%)8.0 (5.2 – 10.8)(5) Oligorecurrent after prior curative-intent therapy, with ST prior to RT20 (15%)4.0 (1.3 – 6.7)(6) Oligorecurrent after prior RT for oligorecurrence15 (11%)4.0 (0.3 – 7.7)(7) De novo widely metastatic with oligoprogression of limited sites while on ST (potentially due to resistant subpopulations of tumor clonogens)15 (11%)3.0 (0.0 – 10.4) Open table in a new tab