Radiotherapy in Older Women with Early-Stage Breast Cancer after Conserving Treatment

the Cancer Therapy Advisor take:

After breast conserving surgery, standard treatment for most older women with early-stage breast cancer is adjuvant whole-breast radiotherapy and adjuvant endocrine treatment.

In research recently reported in Lancet, the authors sought to better understand the impact of not administering whole-breast radiotherapy on patients in this category, specifically in regards to local control in older women at low risk of local recurrence at 5 years.

The research was conducted between April 2003 and December 2009 and 1,326 patients were enrolled. Patients were women age 65 and older who had been diagnosed with breast cancer at an early stage and were identified at being at low risk due to factors such as being hormone receptor-positive, axillary node-negative, T1-T2  up to 3 cm at the longest dimension, and clear margins. Patients with grade 3 tumor histology or lymphovascular invasion, but not both, were also enrolled.

The patients also had previously received breast-conserving surgery and were receiving adjuvant endocrine treatment. The trial was phase 3 and was a randomized controlled study that occurred at 76 centers across four countries. Patients were randomly assigned to two arms, either whole-breast radiotherapy (40–50 Gy in 15–25 fractions [658 patients]) or no radiotherapy (668 patients).

Patients were also stratified by the center where they received treatment with a block size of four. The researchers identified the primary endpoint as ipsilateral breast tumor recurrence, follow up is ongoing and will complete after the 10-year mark of the last randomly assigned patient.

After a 5 year median follow up, there was a 1.3% (95% CI 0.2–2.3; 5 patients) recurrence in ipsilateral breast tumors in patients who received whole-breast irradiation. In patients who did not received radiotherapy treatment, 4.1% (2.4–5.7; 26 patients) experienced recurrence in ipsilateral breast tumors (p=0.0002).

Women who did not received radiotherapy also had a univariate hazard ratio for ipsilateral breast tumour recurrence of 5.19 (95% CI 1.99–13.52; p=0.0007) compared with women who were treated with whole-breast radiotherapy. When comparing the two groups, no differences in regional recurrence, distant metastases, contralateral breast cancers, or new breast cancers were described. Both groups had an overall survival rate of 93.9% (95% CI 91.8–96.0; p=0.34).

During the phase 3 trial, 89 women died, 49 patients in the arm without radiotherapy and 40 patients in the radiotherapy arm; only 8 patients and 4 patients died from breast cancer, respectively.

The researchers concluded that postoperative whole-breast radiotherapy resulted in a statistically significant but modest reduction in local control for women 65 years or older with early breast cancer 5 years after being randomly assigned to treatment.

However, the 5-year rate of ipsilateral breast tumor recurrence is low enough to consider not treating certain patients with radiotherapy.