TOPLINE: 

The 2-year cumulative incidence of sacral fractures after short-course radiation therapy (RT) for rectal cancer was 8.8%, according to findings from a single-institution retrospective study. Notably, most cases were asymptomatic, and female sex and a history of osteoporosis were identified as significant risk factors.

METHODOLOGY:

• Sacral fractures can be a late complication of pelvic RT, but there are limited data on the incidence of these fractures after short-course RT for rectal cancer.
• Researchers conducted a single-institution retrospective study at Johns Hopkins University School of Medicine in Baltimore between 2017 and 2024, analyzing patients with rectal adenocarcinoma who received neoadjuvant short-course RT and consolidation chemotherapy.
• Overall, 171 patients were included in the analysis after excluding those who had received previous pelvic irradiation or lacked follow-up imaging. Patients received 25 Gy in five fractions prescribed to target coverage, with the clinical target volume consisting of the primary rectal tumor, mesorectum, internal iliac and pelvic sidewall nodal regions, and presacral space, without concurrent chemotherapy.
• Posttreatment surveillance imaging (CT or MRI) was reviewed for sacral and other pelvic bone fractures, with median imaging follow-up of 2.2 years.

TAKEAWAY:

• The crude incidence of sacral fractures was 7.6%, with a 2-year cumulative incidence of 8.8% and a median time to fracture of 1.64 years after completion of RT.
• On multivariable analysis, female sex was associated with an increased risk for sacral fracture (adjusted hazard ratio [aHR], 6.01; 95% CI, 1.62-22.3), as was a history of osteoporosis (aHR, 7.37; 95% CI, 2.20-24.7).
• Age, race, BMI, clinical stage, RT technique (three-dimensional conformal vs intensity-modulated RT), and total mesorectal excision surgical management were not independently associated with increased sacral fracture risk.

IN PRACTICE:

“Heightened vigilance during posttreatment follow-up and consideration for bone health optimization strategies before and after radiation therapy should be considered in patients at high risk for fracture,” the study authors wrote.

SOURCE:

The study, with first author Panos A. Papanikolaou, of Johns Hopkins University School of Medicine, was published online in Advances in Radiation Oncology.

LIMITATIONS: 

Patients were not followed up with one consistent imaging approach, and reliance on radiology reports for fracture detection and clinical notes for the presence or absence of associated pain may have underestimated both the true fracture incidence and the incidence of symptomatic fractures. While female sex and known osteoporosis history emerged as statistically significant risk factors on both univariate and multivariable analyses, the estimated model coefficients have wide CIs suggestive of imprecision and should be interpreted with caution. A larger sample size and prospective analyses are needed for further validation of the findings.

DISCLOSURES:

The authors reported no funding sources for this study. Jeffrey J. Meyer disclosed relationships with Springer Media B.V. and UpToDate, Inc., that include consulting or advisory roles, and disclosed receiving funding grants from RayzeBio Inc. Amol K. Narang disclosed receiving funding grants from Flavocure Biotech Inc., Nanocan Therapeutics, and Boston Scientific Corporation. Eric S. Christenson disclosed consulting or advisory relationships with Roche Diagnostics, Sirtex Medical Inc, UroGen Pharma, Parabilis Medicines, and Seres Therapeutics Inc, and disclosed receiving funding grants from Parabilis Medicines; Regeneron Pharmaceuticals Inc.; Affimed GmbH; Haystack Oncology Inc.; Pfizer Inc.; Agenus Inc.; and NextCure, Inc. Additional disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.