Post-Mastectomy Radiotherapy Trial

Research has shown that for cancer patients with positive lymph nodes or positive surgical margins after mastectomy (or both), subsequent radiation therapy lowers the risk of local-regional recurrence.

Dr Wendy Woodard of the department of radiation oncology at the MD Anderson Cancer Centre at Houston, Texas presented the findings to the American Society for Therapeutic Radiology and Oncology annual meeting.

‘At our institution, we do not currently treat patients with one to three positive nodes with radiation therapy,’ she said, ‘but our findings suggest that radiation therapy may be used on a case-by-case basis and that these patients could be entered into clinical trials for radiation therapy”.

The study involved patients treated in five prospective clinical trails with mastectomy followed by doxorubicin-based chemotherapy. They analysed 469 breast cancer patients who were treated with post-mastectomy radiotherapy and 1031 patients who did not receive radiotherapy. The median follow-up was 10 years.

Researchers found that post-mastectomy radiotherapy reduced local-regional recurrence (LRR) rates for all patients regardless of the number of nodes involved.

Specifically, LRR in patients with 20% or more positive lymph nodes was 27% for patients who did not receive radiotherapy compared with 11% for those treated with radiotherapy. For patients with fewer than 20% involved lymph nodes, LRR was 12% in those who received radiotherapy compared with 4.2% in those who did not.

Likewise, in patients with close or positive margins, LRR was 13.3% in those who received radiation therapy and 45% in those who did not (p = 0.01).

Chest wall recurrences were reduced from 68% to 6.4% with the addition of radiation, and supraclavicular recurrences were reduced from 41% to 3.4%.

In patients treated with radiotherapy, pathologic size of the largest involved node, oestrogen receptor status, and lymph-vascular space invasion were significant predictors of LRR.

Dr. Woodward pointed out that patients who did not receive radiotherapy compared to those who did started out with significantly less favorable prognostic factors, including a higher number of positive nodes and larger tumor size, yet they saw a benefit in this group nonetheless.

‘This is one of the first studies to demonstrate reduction of LRR with radiation in patients with adequate axillary dissection and doxorubicin-based therapy,’ she said. ‘But a randomised trial is needed to see whether stage T1/2 patients with 1 to 3 positive lymph nodes would benefit from post-mastectomy radiation.’

(Source: Reuters Health)