Local control of bone metastases treated with external beam radiotherapy in recent years: a multicenter retrospective study

Our plain-English summary of Local control of bone metastases treated with external beam radiotherapy in recent years: a multicenter retrospective study, by K. Makita, Y. Hamamoto, H. Kanzaki, et al (Radiation Oncology, 2021).

The study

• Authors: K. Makita, Y. Hamamoto, H. Kanzaki, M. Kataoka, S. Yamamoto, K. Nagasaki, H. Ishikawa, N. Takata, S. Tsuruoka, K. Uwatsu, T. Kido
• Journal: Radiation Oncology
• Published: 2021;16(1):225
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Over the past decades, remarkable advancements in systemic drug therapy have improved the prognosis of patients with bone metastases. Individualization is required in external beam radiotherapy (EBRT) for bone metastases according to the patient's prognosis. To establish individualized EBRT for bone metastases, we investigated factors that affect the local control (LC) of bone metastases.

Methods: Between January 2010 and December 2019, 536 patients received EBRT for 751 predominantly osteolytic bone metastases. LC at EBRT sites was evaluated with a follow-up computed tomography. The median EBRT dose was biologically effective dose (BED10) (39.0) (range of BED10: 14.4-71.7 Gy).

Results: The median follow-up time and median time of computed tomography follow-up were 11 (range 1-123) months and 6 (range 1-119) months, respectively. The 0.5- and 1-year overall survival rates were 73% and 54%, respectively. The 0.5- and 1-year LC rates were 83% and 79%, respectively. In multivariate analysis, higher age (≥ 70 years), non-vertebral bone metastases, unfavorable primary tumor sites (esophageal cancer, colorectal cancer, hepatobiliary/pancreatic cancer, renal/ureter cancer, sarcoma, melanoma, and mesothelioma), lower EBRT dose (BED10 < 39.0 Gy), and non-administration of bone-modifying agents (BMAs)/antineoplastic agents after EBRT were significantly unfavorable factors for LC of bone metastases. There was no statistically significant difference in the LC between BED10 = 39.0 and BED10 > 39.0 Gy.

Conclusions: Regarding tumor-related factors, primary tumor sites and the sites of bone metastases were significant for the LC. As for treatment-related factors, lower EBRT doses (BED10 < 39.0 Gy) and non-administration of BMAs/antineoplastic agents after EBRT were associated with poor LC. Dose escalation from BED10 = 39.0 Gy did not necessarily improve LC.

© 2021. The Author(s).

In plain English

This was a multicenter retrospective study from three hospitals in Ehime, Japan. It examined how often bone metastases (cancer that has spread to bone) treated with external beam radiotherapy stayed stable or shrank afterward, which the authors called local control. It included 536 patients with 751 mainly bone-destroying (osteolytic) metastases, treated between January 2010 and December 2019 and followed with CT scans. The most common dose was 30 Gy in 10 fractions. Treated sites were controlled in 83% at 6 months and 79% at 1 year, and regrowth was seen at 19.6% (147/751) of sites. In the multivariate analysis, poorer control was associated with age 70 or older, metastases outside the spine, doses below a BED10 of 39.0 Gy (the level of 30 Gy in 10 fractions), the primary cancer group, and not receiving bone-modifying or anticancer drugs after radiotherapy. Mesothelioma was not analyzed on its own. It was grouped with sarcoma and melanoma (18 lesions), and this combined group had 84% control at 1 year. Doses above a BED10 of 39.0 Gy did not give a statistically significant improvement over 39.0 Gy. The authors concluded that tumor and treatment factors were associated with local control.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Multicenter retrospective study
• Who was studied: 536 patients with 751 predominantly osteolytic bone metastases, treated with radiotherapy between January 2010 and December 2019 at Shikoku Cancer Center, Ehime University Hospital and Saiseikai Imabari Hospital, Japan, and followed with CT. The most common primary cancers were lung and breast. Sarcoma, melanoma and mesothelioma together made up 18 lesions (2.4%).
• Exposure: External beam radiotherapy to bone metastases. The most common schedule was 30 Gy in 10 fractions (BED10 39.0 Gy), with a range of BED10 14.4 to 71.7 Gy. Use of bone-modifying agents and anticancer drugs after radiotherapy was also examined. No asbestos or fiber exposure was studied.
• Main results:
  • Overall survival for all patients was 73% at 6 months and 54% at 1 year.
  • Local control of treated sites was 83% at 6 months and 79% at 1 year.
  • Local recurrence occurred at 19.6% (147/751) of treated sites.
  • By primary cancer group, 1-year local control was 47% in the unfavorable group (esophageal, colorectal, hepatobiliary/pancreatic), 77% in the moderately unfavorable group (kidney/ureter, sarcoma/melanoma/mesothelioma) and 87% in the favorable group.
  • The combined sarcoma/melanoma/mesothelioma group had local control of 84% at 6 months, 84% at 12 months and 28% at 36 months. Mesothelioma was not reported separately.
  • Age 70 or older was associated with poorer local control in the multivariate analysis (HR 2.34, 95% CI 1.62 to 3.40).
  • One-year local control was 86% for vertebral (spine) metastases and 69% for non-vertebral metastases. In the multivariate analysis, the hazard ratio for non-vertebral versus vertebral sites was 1.78 (95% CI 1.24 to 2.57).
  • A dose below BED10 39.0 Gy was associated with poorer local control in the multivariate analysis (HR 2.08, 95% CI 1.31 to 3.30).
  • There was no statistically significant difference in local control between BED10 equal to 39.0 Gy and BED10 above 39.0 Gy.
  • Not receiving bone-modifying agents after radiotherapy (multivariate HR 1.94, 95% CI 1.34 to 2.83) and not receiving antineoplastic agents after radiotherapy (HR 1.58, 95% CI 1.08 to 2.31) were associated with poorer local control.
• The authors' conclusion: The authors concluded that primary tumor site and the site of the bone metastasis were significant for local control. They also concluded that lower doses (BED10 below 39.0 Gy) and not giving bone-modifying or anticancer drugs after radiotherapy were associated with poor local control, and that raising the dose above BED10 39.0 Gy did not necessarily improve control.
• Limitations the authors state:
  • Osteoplastic (bone-forming) metastases were excluded because local control is hard to evaluate in them. As a result, many prostate cancer metastases were left out.
  • The number of lesions for each primary tumor site was relatively small, so local control by primary site may not have been evaluated accurately.
  • There may have been selection bias in how doses were chosen, because many radiation oncologists were involved over a long period at several centers.
  • Pain information was unavailable for many patients, so the link between regrowth and pain could not be evaluated.

Topics

Medical terms in this study, explained in our Lexicon: Prognosis, Overall Survival, Multivariate Analysis, Esophageal Cancer, Colorectal Cancer, Sarcoma, Mesothelioma.

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