Contralateral Prophylactic Mastectomy Improves Survival, Is Cost-Effective in Some

Caroline Helwick

November/December 2010, Vol 1, No 6 - ASCO Breast Cancer Symposium


National Harbor, MD—Multiple benefitswere observed for contralateral prophylactic mastectomy (CPM), including cost-effectiveness, in studies presented at the 2010 ASCO Breast Cancer Symposium by investigators from the Mayo Clinic, Rochester, MN.

CPM not only reduced the risk of breast cancer in the opposite breast by 95% among high-risk women with breast cancer, it improved survival as well. In addition, in younger women undergoing mastectomy and deemed to be at average risk, CPM was costeffective when compared with routine surveillance aimed at early detection for cancer in the opposite breast.

“CPM provides good value, ie, cost/outcome, for select patient groups,” reported Benjamin Zendejas, MD, of the Department of Surgery at the Mayo Clinic, who authored the cost-effectiveness study

CPM Improves Survival


Women undergoing mastectomy for breast cancer frequently opt for CPM. In fact, the rate of CPM has more than doubled over the past decade, said Judy Boughey, MD, principal investigator of the survival analysis.

Although CPMis known to decrease the occurrence of contralateral breast cancer by 90% to 95%, debate continues regarding any survival advantage with CPM, because there are limited and conflicting data and a lack of long-term follow-up, she said. The aim of Dr Boughey’s study was to investigate whether CPM is associated with improved survival in women with a family history of breast cancer undergoing mastectomy for stage I or II breast cancer and CPM as well.

All CPMs were performed at the Mayo Clinic in Rochester, MN, between 1971 and 1993, offering a look at the long-term outcomes of 385 highrisk patients who were matched 1:1 with a comparison cohort of 385 women having unilateral mastectomy and no CPM. Patients were matched according to age at diagnosis, year of diagnosis, tumor stage, and nodal status, although a family history of breast cancer was present for all the study population but only 35% of the unilateral mastectomy group.

At a median follow-up of 17.3 years, only 2 patients (0.5%) in the CPM cohort developed contralateral breast cancer compared with 31 patients (8.1%) in the unilateral mastectomy cohort. This amounted to a 95% decrease in the risk of contralateral breast cancer (P <.001), Dr Boughey reported.

“The result remained strongly significant after adjusting for age, stage, nodal status, and first-degree family history,” she noted.

The 10-year overall survival estimates were 83% for the CPM group and 74% for the unilateral mastectomy group. After multivariate analysis, the reduction in the risk of death remained significant at 23% (P = .03). The disease free survival difference between the 2 cohorts was also statistically significant, with a 33% reduction resulting from CPM in the multivariate analysis (P = .0005), according to Dr Boughey.

“We conclude that CPM significantly decreases the risk of contralateral events. Additionally, this study shows an association between CPM and improved survival and disease free survival and a trend toward improved breast cancer– specific survival,” she said.

 

Cost-Effectiveness Shown
Dr Boughey and her colleagues also showed that CPM is cost-effective for younger patients at average risk, and for high-risk patients (BRCA positive) at any age. The study’s first author was Benjamin Zendejas, MD.

“This study represents the first costeffectiveness analysis comparing CPM to routine surveillance for patients with unilateral breast cancer,” Dr Zendejas noted.

They used a Markov model to simulate the management of breast cancer patients from treatment (mastectomy) to death. All model parameters were gathered from published literature or national databases. Base-case analysis included end-of-life costs and focused on average risk breast cancer patients with a starting age at treatment of 45 years. Costs were reported in 2007 US dollars. Outcomes were valued in quality adjusted life-years (QALYs). Patients’ ages at treatment and breast cancer risk level were varied to assess their impact on the overall results.

The main comparison was the CPM strategy versus surveillance, which included annual mammography with computer-aided detection.

The analysis found that mean total breast cancer–related costs for women aged 45 to 60 years are comparable: $30,222 for the CPM strategy and $29,076 for the surveillance strategy (Table). The CPM strategy provides 22.52 mean QALYs (ie, years in perfect health) compared with 22.44 for the surveillance strategy, resulting in an incremental cost-effectiveness ratio of $12,733 per QALY gained for CPM when compared with surveillance, Dr Zendejas reported.

“Base-case results show CPM to be cost-effective in the younger agegroups (ie, <65 years of age). As expected, the rate of new contralateral breast cancers is significantly lower for the CPM group,” he noted.

The model estimated that, on average, 5 prophylactic mastectomies would be needed to prevent the occurrence of 1 contralateral breast cancer. For the general population of breast cancer patients aged ≥65 years, however, CPM is less cost-effective, because its incremental cost-effectiveness ratio is above the $50,000 threshold for costeffectiveness, the study found.

For BRCA-positive breast cancer patients, the CPM strategy is not only cost-effective but it is also a cost-saving strategy that provides “more QALYs while being less costly when compared to routine surveillance,” Dr Zendejas pointed out.