Size matters: second breast cancer size following treatment for primary cancer as a predictor of survival

Introduction

The purpose of surveillance mammography following primary breast cancer treatment is to detect subsequent cancers at the smallest size. We examined the prognostic effect of size of ipsilateral breast tumour recurrence (IBTR) and metachronous contralateral breast cancer (MCBC) to assess potential benefit of surveillance mammography after breast cancer treatment.

Methods

Second cancers (IBTR n = 1,174, MCBC n = 975) diagnosed between 1 January 1990 and 31 January 2007 from the West Midlands Cancer Intelligence Unit Breast Cancer Registry were analysed. Survival from diagnosis of second cancer was examined using Cox regression models. Risk factors included were prognostic factors of the primary tumour and size of the second tumour. Outcomes were time to all-cause death and to breast cancer death. Estimates are hazard ratios (HRs) and 95% confidence intervals.

Results

There were 613 all-cause deaths and 422 breast cancer deaths after IBTR. For both outcomes, second cancers >2 cm had poorer prognosis compared with those <1 cm, HRs were 1.75 (1.29 to 1.37) and 1.99 (1.37 to 2.89). In MCBC there were 358 all-cause deaths, HR 2.14 (1.49 to 3.06), and 23 breast cancer deaths, HR 1.99 (1.38 to 2.83).

Conclusions

With either IBTR or MCBC the size of the second tumour is important, patients with cancers >2 cm in diameter being at a significantly greater risk of death. Lead-time bias from the mode of detection may be a factor in these results. The frequency of surveillance mammography should be considered for maximum benefit.