Adjuvant radiotherapy after mastectomy for pT1-pT2 node negative (pN0) breast cancer: is it worth the effort?

Purpose: Postoperative radiotherapy (RT) for pT1-2 pN0 breast cancer was the standard treatment in our department. Since little data on the importance of RT in this subgroup are known, we reviewed the clinical records with regard to overall survival.

Material And Methods: From 1984 until 2000, 1789 files were submitted to retrospective analyses; 731 had a pT1 (n=427) or pT2 (n=304) pN0 lesion. They were treated with breast conserving surgery (BCS) (n=343) or mastectomy (ME) (n=388), axillary lymph node dissection (ALND) and post-operative RT. The outcome was analyzed and compared with the patients included in the SEER-Data 1988-1997 (NCI-Surveillance, Epidemiology and End Results, release 2000) that were treated according to the standard treatment: BCS+ALND+RT, or ME+ALND no RT.

Results: The actuarial overall survival (OS) at 5 and 10 years after BCS was 93.3% and 85.1% for pT1 and 88.3% and 75.4% for pT2 tumors. These results are comparable with the SEER (93.9%, 84.9% for pT1, and 87.3%, 76.7% for pT2, respectively). For our ME patients the OS was 91.8% and 79.9%, respectively (pT1 at 5 and 10 years, respectively), and 83.6% and 70.4% (pT2 at 5 and 10 years). In the SEER data the analyses resulted in 89.3% and 73.8% (pT1), and 81.1% and 63.5% (pT2), respectively.

Discussion: Although both databases are retrospective, the comparable survival in BCS patients pleads for the similarity of the two populations. The better OS observed in ME patients treated with RT compared to the SEER patients argues in favor of a benefit due to adjuvant radiotherapy.

Conclusion: Radiotherapy after mastectomy might improve survival in low-risk node negative patients. Our data shows an absolute benefit of between 2.5% and 6.9% OS in favor of post ME radiotherapy, compared to the SEER data.