Background: The effectiveness of routine postoperative irradiation following breast-conserving treatment of breast cancer has not previously been assessed in randomized clinical trials that have taken place in settings where mammography has been a major pathway to diagnosis or that have followed patients treated surgically by sector resection.
Purpose: The aim of this study was to determine if treatment of stage I breast cancer by strictly standardized surgical technique with meticulous confirmation of a complete excision can reduce the local recurrence rate to an acceptable level without routine adjuvant radiotherapy.
Methods: In this trial conducted in Sweden, 381 women with stage I breast cancer were surgically treated by sector resection plus axillary dissection; then 184 women were randomly selected to receive postoperative radiotherapy to the breast (XRT group), and 197 women received no further treatment (non-XRT group). Patient accrual started in October 1981 and ended in September 1988. Criteria for eligibility were a unifocal cancer 20 mm or less in diameter (visible on mammogram) and radical excision and no histopathologic signs of axillary metastases.
Results: After median follow-up times of 65 and 63 months, the 5-year local recurrence rate was 2.3% (95% confidence interval [CI] = 0.1%-4.3%) in the XRT group and 18.4% (95% CI = 12.5%-24.2%) in the non-XRT group, respectively. The life-table curves were significantly different (P = .0001). The two treatment groups did not differ in overall survival: For the XRT group, the value was 91.0% (95% CI = 86.4%-95.4%); for the non-XRT group, it was 90.3% (95% CI = 85.8%-94.8%). The same was true for survival free from regional and distant recurrence: XRT group, 90.0% (95% CI = 85.3%-94.5%); non-XRT group, 87.1% (95% CI = 82.3%-92.0%). The rate of local recurrences was significantly higher in patients treated more recently (P. = 003).
Conclusions: Sector resection plus radiotherapy to the breast very effectively achieves local tumor control. Surgery alone results in similar survival prospects, but the probability of local recurrence approaches 20% at 5 years.
Implications: The increase in recurrence rate observed over time suggests that surgical technique and patient selection should be improved. The benefits of reduced cost and patient inconvenience that would result from the elimination of postoperative radiotherapy must be carefully weighed against the disadvantages of local recurrence. Longer term follow-up must be done to estimate the risk of cancer recurrence in these women 10 and 15 years later, and methods must be developed to identify those women who have a higher risk of recurrence. Finally, economic analyses of this and similar trials are needed to give empirical underpinnings for optimal use of radiotherapy.