Efficacy and Safety of Local Radiotherapy to All Oligometastatic Sites in Elderly Patients with Metachronous Oligometastatic Cancers After Initial Treatment for the Primary Tumor

Abstract

Background and purpose: This study aimed to investigate the efficacy and safety of maintenance therapy combined with local radiotherapy at all oligometastatic sites (LRTOS) in elderly patients with metachronous oligometastatic cancers (MOC).

Patients and methods: A total of 242 elderly patients with MOC (≤5 metastases) and primary tumor well controlled after definitive treatment was retrospectively analyzed between August 2014 and February 2020 at Beijing Geriatric Hospital and Air Force General Hospital. Patients were divided into maintenance therapy group (maintenance therapy alone) and local radiotherapy group (maintenance therapy combined with LRTOS).

Results: There were 86 patients in the local radiotherapy group and 156 patients in the maintenance therapy group. The median length of follow-up was 36 months (range, 8.0-62 months). Median overall survival (mOS) was 25 months (95% CI: 21.1-28.9) in the local radiotherapy group and 16 months (95% CI: 14.5-17.6) in the maintenance therapy group (p < 0.001). Multivariate analyses demonstrated that LRTOS (hazard ratio (HR) = 0.49, 95% confidence interval (CI): 0.35-0.67, p < 0.001), good Eastern Cooperative Oncology Group Performance Status (ECOG PS, HR = 0.69, 95% CI: 0.49-0.97, p = 0.032), longer duration between diagnosis of primary tumor and occurrence of progression (HR = 0.87, 95% CI: 0.78-0.97, p = 0.015), and subsequent systemic treatment (HR = 0.52, 95% CI: 0.38-0.72, p < 0.001) were independent predictors of good OS. In patients who did not receive subsequent systemic treatment, their mOS was 21 months (95% CI: 12.8-29.2) for those treated with LRTOS and 14 months (95% CI: 11.4-16.6) for those who did not receive local radiotherapy (p = 0.001). Further multivariate analysis showed that LRTOS was the only independent factor for predicting good OS (HR = 0.47, 95% CI: 0.26-0.83, p = 0.010). Patients with metachronous oligometastatic lung cancer, colorectal cancer, prostate cancer, and breast cancer had higher survival benefits following LRTOS. Most patients suffered from grade 1-2 toxicities, but no treatment-related death was recorded.

Conclusion: This retrospective study shows that elderly patients with MOC treated with LRTOS may have better survival outcomes.

Keywords: elderly patients; local radiotherapy; metachronous oligometastatic cancers; residual disease.

Figure 1

A flowchart of the study.

Figure 2

Overall survival of patients in the local radiotherapy and maintenance therapy groups.

Figure 3

Overall survival of patients who received local radiotherapy at all oligometastatic sites and those who did not receive subsequent systemic treatment.

Figure 4

Overall survival associated with ECOG PS 0–1 vs 2 (A), diagnosis of TNM stages I, II, and III (B), number of metastases 1–2 vs 3–5 (C), and subsequent treatment yes vs no (D).

Figure 5

Multivariate analysis of the prognosis of elderly patients with metachronous oligometastatic cancer. OS*= oligometastatic sites, time to progression^# = time from diagnosis of the primary tumor to progression.

Figure 6

Overall survival for each type of primary tumor. Lung cancer (A), colorectal cancer (B), prostate cancer (C), breast cancer (D), cervical cancer (E), and other cancers (F). Other cancers = larynx cancer (n = 2), pancreatic cancer (n = 3), stomach cancer (n = 2), liver cancer (n = 1).