TOPLINE:
There may be no threshold dose below which radiation to cardiac substructures does not increase the risk for later cardiac diseases in children with cancer.
METHODOLOGY:
-
Review of 25,481 patients in the Childhood Cancer Survivor Study who had no cardiac complications in the first 5 years following cancer treatment from 1970-1999; nearly half (48.2%) had been exposed to radiotherapy.
-
Radiation doses to the coronary arteries, heart chambers, heart valves, and whole heart were calculated based on radiotherapy records.
-
Median age at follow up was 29.8 years and ranged from 5.6 to 65.9 years.
TAKEAWAY:
-
Mean radiation doses of 5.0–9.9 Gy to the whole heart did not increase the risk for later cardiac disease.
-
Mean doses of 5.0–9.9 Gy to the right coronary artery (rate ratio [RR], 2.6) and left ventricle (RR, 2.2) did increase the risk for subsequent coronary artery disease.
-
Mean doses of 5.0–9.9 Gy to the tricuspid valve (RR, 5.5) and right ventricle (RR, 8.4) increased the risk for later valvular disease.
-
Linear modeling adequately described the dose-response relationship for many cardiac substructures, suggesting there is no threshold dose necessary for cardiac damage.
IN PRACTICE:
“These findings solidify the need to consider cardiac substructure doses in [pediatric] radiation treatment planning and in survivorship care. Future work to ascertain optimal cardiac dose constraints, especially in the era of highly conformal [radiotherapy] techniques such as [intensity-modulated radiotherapy] and proton therapy, remains critical,” the authors conclude.
STUDY DETAILS:
The study was led by James Bates, MD, of Emory University, Atlanta, and published June 12 in the Journal of Clinical Oncology.
LIMITATIONS:
-
Chronic conditions were self-reported.
-
Current radiotherapy techniques are much more precise than in the decades when these cancer survivors were treated, allowing preferential sparing of various heart structures.
-
The study did not assess other treatments and lifestyle issues that may have affected heart health.
DISCLOSURES:
The work was funded by the National Cancer Institute. Investigators reported ties to Doximity, Abbott, Merck, Grail, and other companies.
Source: Read Full Article
