Local Recurrence Less Likely With Mastectomy in Younger Breast Cancer Patients

Over the long term, local recurrence is more likely in young women with invasive breast cancer who undergo breast conserving surgery (BCS) compared with those who undergo mastectomy, though survival is no different, according to a new study. Also, achieving clear surgical margins and the use of post-mastectomy chest wall radiotherapy (RT) was more important than extent of surgery for positive outcomes.

The two surgical options “have been looked at in randomized controlled trials, but they’ve always had very small numbers of young women,” said Tom Maishman, of the University of Southampton in the United Kingdom. He presented the study during a poster discussion session at the San Antonio Breast Cancer Symposium, held December 6–10.

The new study included 2,882 women included in the POSH trial, which involves only women aged 18 to 40 years. Approximately half underwent mastectomy (n = 1,464) and half underwent BCS (n = 1,395); mastectomy patients were more likely to have estrogen receptor– or progesterone receptor–positive disease, and were more likely to be HER2-positive as well. Mastectomy patients were also more likely to have multifocal disease than BCS patients (46.5% vs 12.5%; P < .001).

At 18 months, the rate of local recurrence was similar between the two groups (1% vs 1%). At 5 years, though, the rates had separated, with a 5.33% rate of local recurrence in BCS patients and 2.63% in mastectomy patients, for a hazard ratio (HR) of 3.39 (95% CI, 2.03–5.66; P < .001). At 10 years they separated further, at 11.68% in BCS patients and 4.93% in mastectomy patients, for an HR of 5.27 (95% CI, 2.43–11.43; P < .001).

Distant metastases and mortality were better with BCS, but adjustment for prognostic factors eliminated this difference.

The use of chest wall RT in patients who underwent mastectomy yielded lower risk of local recurrence. At 10 years, those who underwent RT had a recurrence rate of 6.45%, compared with 4.06% in those who did not, for an HR of 0.46 (95% CI, 0.24–0.86; P = .015). In BCS patients positive surgical margins were associated with poorer rates of distant metastases and overall survival (P < .001).

“Achieving clear surgical margins and appropriate post-mastectomy chest wall RT appears more important than the extent of surgery for positive outcomes in young women with breast cancer,” Maishman concluded.

Ann Partridge, MD, MPH, of the Dana-Farber Cancer Institute in Boston, was the discussant for the session, and noted that an important question is that of heredity, meaning whether or not the local recurrences are actually new primary tumors.

“I think these data confirm what has now been incorporated into international guidelines, which is in young women we really need to pay attention to margins,” Partridge said. Also, she stressed that the growing body of radiation oncology literature suggest there is substantial benefit with RT in young patients.