Postoperative Radiotherapy May Not Reduce Long-Term Breast Cancer Recurrence Risk

Radiotherapy did not significantly reduce recurrence risk in certain patients with breast cancer, research showed.

Receiving postoperative radiotherapy did not significantly reduce the risk of recurrence in patients with early breast cancer compared with patients who did not receive radiotherapy, researchers found.

In a retrospective study published in The Lancet, a trial included 585 patients who were randomly assigned to two treatment groups between April 1985 and October 1991. The first group treated 291 patients with radiotherapy, while the 294 patients in the second group did not receive radiotherapy. The median follow-up was 17.5 years.

Researchers found that ipsilateral breast tumor recurrence (cancer returning to the same breast as the initial diagnosis) was significantly lower in the group that received radiotherapy, versus the no radiotherapy group. Of note, subsequent risks of ipsilateral breast tumor recurrence were similar in patients from either treatment group, researchers found.

“The 30-year follow-up of the studies shows that most benefit in reducing the risk of cancer recurring in the same breast is achieved in the first decade of follow-up,” Ian Kunkler said in an email interview with CURE®. “After the first decade, there is little benefit from radiotherapy in reducing the risk of local recurrence. The long-term survival of patients treated with or without radiotherapy was similar.”

Kunkler is a professor and consultant in Clinical Oncology at the Edinburgh Cancer Centre, University of Edinburgh in Scotland.

He spoke with CURE® about the process of postoperative radiotherapy, survival outcomes and what patients should know about the study’s findings.

CURE®: Can you explain the process of radiotherapy postoperatively for patients with early-stage breast cancer?

Kunkler: Patients considered suitable for postoperative radiotherapy undergo planning of the radiotherapy fields to the breast — and if necessary — to the regional nodes if sentinel node biopsy shows limited evidence of breast cancer spread. The radiation beams, [which are] delivered by the treatment machines, are selected to provide a homogeneous distribution of X-rays within the target areas, while minimizing dose to critical structures such as the heart.

Most patients are treated with short courses of radiotherapy with between five to 15 treatments over one to three weeks. Patients are regularly monitored for any toxicity during treatment and at follow-up visits.

The conclusion of the study noted that patients who experience a late relapse 10 or more years after breast-conserving surgery might only have little gain from postoperative radiotherapy. Can you talk a bit more about this?

Our findings imply that patients whose breast tumor biology predicts late local relapse after the first decade of follow-up gain little from radiotherapy. These late recurrences, which often have a better prognosis than recurrences within the first five years of follow-up, will require anti-cancer drug treatment matched to the characteristics of the recurrence.

What were some of the outcomes regarding overall survival and recurrences within your study?

Radiotherapy reduced the risk of local recurrence at 10 years of follow-up from 36% in the nonirradiated group to 16% in the irradiated group.

Average overall survival in both arms of the trial was similar (19.2 years with radiotherapy and 18.7 years without radiotherapy). There were fewer deaths from breast cancer in the irradiated patients (37%) compared to no radiotherapy (46%), although there were more deaths from other cancers in the irradiated group (11%) than in the no radiotherapy group (20%).

What advice or takeaways would you give this patient population regarding postoperative radiotherapy?

Patients should be reassured that radiotherapy is beneficial (it reduces the risk of recurrence in the breast by nearly 40% in the first decade of follow-up). However, like most anti-cancer treatments, radiotherapy has finite benefits and loses its effect in reducing local recurrence beyond the first decade of follow-up.

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