Irradiated Volume, Smoking Linked to Breast Induration Risk

TOPLINE:
The risk for breast induration is associated with the volume of irradiated breast tissue in patients aged 65 years or older, but not in those aged 50-64 years, according to a recent study. The researchers did, however, observe a dose-volume relationship for patients younger than 50 years who received a boost and found that smoking doubled the risk for breast induration, regardless of irradiated volume or age.
METHODOLOGY:
Breast induration is a common side effect of radiotherapy, particularly in patients with larger breasts. The Danish Breast Cancer Group (DBCG) partial breast irradiation trial found the volume of breast tissue irradiated to a certain dose, not the size of the breast itself, was associated with an increased risk for breast induration in older patients.
A secondary analysis of another DBCG trial, DBCG HYPO, investigated the relationship between irradiated breast volume, radiation dose, patient age, smoking status, and boost treatments in a larger population that included younger patients.
Researchers analyzed treatment plans from 1333 Danish patients (age, 41 years or older) with T1-2 NO-N1 invasive adenocarcinoma or ductal carcinoma in situ in the DBCG HYPO trial.
Patients were randomly assigned to receive whole breast irradiation of either 50 Gy in 25 fractions (n = 659) or 40 Gy in 15 fractions (n = 674), with a sequential boost of 2 Gy in five to eight fractions for patients younger than 50 years or for those with a narrow (< 2 mm) resection margin.
Overall, 1135 patients received only whole breast irradiation, while 198 received a boost (156 patients younger than 50 years had 10 Gy and 42 patients aged 50 years or older had 16 Gy).
TAKEAWAY:
Researchers observed a significant association between the volume of breast tissue irradiated and the occurrence of grade 2-3 induration 3 years after radiotherapy in patients aged 65 years or older. Specifically, the risk for breast induration was higher for larger irradiated volumes than for smaller ones (22% vs 10%; P = .005). However, this elevated risk did not extend to patients aged 50-64 years.
Among patients aged 50-64 years, those who received a lower dose (40 Gy) had a slightly lower risk for induration (10%) than those who received 50 Gy (13%), but the radiation dose did not affect the overall risk for induration (16% vs 17%) for patients aged 65 years or older.
Smoking doubled the risk for induration, irrespective of age and the volume of breast tissue irradiated.
In patients aged 41-49 years who received a boost, researchers observed a significant dose-volume effect on the risk for induration. The rate of induration increased from 5% for smaller irradiated volumes (< 220 mL) to 21% for larger volumes (> 220 mL) (P = .002).
IN PRACTICE:
“To the best of our knowledge, this is the first report to show a clear association between treated breast volume (not bra size) measured in mL, dose and age,” the authors wrote, adding that “our findings support a hypothesis that repair of normal tissue damage decreases with increasing age, or normal tissue damage is more pronounced in older age.” The authors also noted that “these results are important in the shared decision making with breast cancer patients in general.”
SOURCE:
This study, led by Mette S. Thomsen, Aarhus University Hospital, Aarhus, Denmark, was published online in Radiotherapy and Oncology.
LIMITATIONS:
This study’s limitations included the restriction to Danish patients, which may limit generalizability to other populations. Additionally, the small number of patients older than 50 years receiving a boost limited the statistical power for this subgroup.
DISCLOSURES:
The authors did not disclose any funding information or relevant financial interests or personal relationships that could have influenced the study.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
 
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