Prognostic Score Helps Target Post-Op Radiotherapy To High-Risk DCIS Patients

Recurrence risk scoring system may allow some ductal carcinoma in situ patients to avoid radiotherapy after breast-conserving surgery

medwireNews: Researchers have devised a recurrence risk scoring system to identify ductal carcinoma in situ (DCIS) patients who will derive a significant survival benefit from radiotherapy after breast-conserving surgery (BCS).

Yasuaki Sagara, from Brigham and Women’s Hospital in Boston, Massachusetts, USA, and co-workers showed that breast cancer mortality after DCIS was low overall, with 304 breast cancer-specific deaths among the 32,144 patients in the Surveillance, Epidemiology, and End Results database who were treated between 1988 and 2007, and followed-up for a median of 96 months.

And there was significantly better survival among the 20,329 patients who received radiotherapy after BCS than the 11,815 women who did not, with 10-year breast cancer mortality rates of 1.8% versus 2.1%.

However, the team detected a “possible heterogeneous treatment effect” of radiotherapy, finding that the survival benefit associated with adjuvant radiation was only significant for younger patients and those with a high nuclear grade and/or large tumour.

Indeed, when these markers were combined into a prognostic score, there was a significant correlation between prognostic score and the magnitude of benefit with radiotherapy.

Thus, among patients who had a low prognostic score of 1, breast cancer mortality rates were comparable for women who did and did not receive radiotherapy. By contrast, there was about a 70% reduction in breast cancer mortality for patients with a high score of 4 or 5 who received radiotherapy compared with those who did not, translating to an absolute difference in the 10-year breast cancer mortality rates of 1.9% and 4.0%, respectively.

“Our results suggest that the omission of [radiotherapy] for patients with low prognostic scores is safe, given that it does not seem to improve survival compare[d] with BCS alone”, the team writes in the Journal of Clinical Oncology.

The researchers observe, however, that the overall breast cancer mortality rate in the study was just 0.9%, whereas the mortality rates for other malignancies and heart disease were both 2.6% and for other noncancer causes 4.9%.

“These results, when taken together with our earlier findings on DCIS, suggest that further research investigating the overdiagnosis and overtreatment of breast cancer is warranted and that a less invasive and more individualized local treatment strategy on the basis of one’s probability of local recurrence should be considered”, they conclude.

Reference

Sagara Y, Freedman RA, Vaz-Luis I, et al. Patient prognostic score and associations with survival improvement offered by radiotherapy after breast-conserving surgery for ductal carcinoma in situ: A population-based longitudinal cohort study. J Clin Oncol 2016; Advance online publication 1 February. doi: 10.1200/JCO.2015.65.1869

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