Contralateral Prophylactic Mastectomy Offers ‘Very Modest’ Survival Benefit

Prophylactic mastectomy provides only a “very modest” survival benefit for women at average risk of contralateral primary breast cancer

medwireNews: Contralateral prophylactic mastectomy (CPM) extends 20-year survival by no more than 1% in women with an average risk of developing a second primary breast cancer in their healthy breast, research suggests.

The Markov model decision analysis, published in the Journal of the National Cancer Institute, used data from the Surveillance, Epidemiology, and End Results study and other reports to calculate the increase in life expectancy (LE) that could be expected by undergoing CPM versus no contralateral surgery.

For women with stage I breast cancer, the LE gain associated with choosing CPM was between 0.13 and 0.59 years, depending on Oestrogen receptor (ER) status and patient age. For patients with stage II disease, the range was 0.08 to 0.29 years.

This means, for example, that a 40-year-old woman with stage I ER-negative breast cancer who chose to undergo CPM would have a 1.8% lifetime risk of developing contralateral breast cancer (CBC) and, on average, would live for 36.44 years without CBC and 0.32 years with CBC.

This compares with a lifetime risk of CBC of 16.4% for the same woman who did not undergo CPM, giving an average 33.20 years of life without CBC and 2.97 years with CBC, explain Todd Tuttle and team, from the University of Minnesota in Minneapolis, USA.

The absolute difference in 20-year overall rates for women who chose to undergo CPM and those who did not varied from 0.56% to 0.94% for women with stage I disease and from 0.36% to 0.61% for those with stage II disease. And 20-year disease-free survival rates were 4.25% to 7.20% and 2.73% to 4.62%, respectively.

And even when adjusting CBC rate and CPM efficacy to give a best-case scenario for CPM, the maximal survival benefit over 20 years was just 1.45%, far lower than that predicted by data from previous studies, the authors say.

“Survival estimates derived from our model may be useful for physicians and breast cancer patients to arrive at evidence based informed decisions regarding CPM”, the team suggests.

“Moreover, the use of accurate and easily understood decision aids may reverse some of the mastectomy trends recently observed in the United States.”

Stephen Pauker and Mohamed Alseiari, from Tufts Medical Center in Boston, Massachusetts, USA, note in an accompanying editorial that decision models often produce surprisingly small differences between even “obvious” treatment decisions.

However, they write that the difference in average survival for women who do and do not undergo CPM in the current study is “very modest” indeed, adding up to no more than another 7 months of survival.

Nevertheless, the editorialists note that the current study only refers to women at average risk of contralateral breast cancer.

“In women at substantially higher risk (based either on family history or genetics), the benefit of CPM might be far greater, and CPM might be a good choice for the patient or for society”, they add.

References

Portschy P, Kuntz K, Tuttle T. Survival outcomes after contralateral prophylactic mastectomy: A decision analysis. JNCI 2014; 106(8):dju160. DOI:10.1093/jnci/dju160

Pauker S, Alseiari M. How big is big enough? Thinking about contralateral prophylactic mastectomy. JNCI 2014; 106(8):dju175. DOI:10.1093/jnci/dju175