What were the findings of the Dutch trial in breast cancer comparing mastectomy versus lumpectomy with radiation?

The Dutch Trial in Breast Cancer: Breast-Conserving Surgery Plus Radiotherapy vs Mastectomy

Key Findings

The Dutch population-based study demonstrated that breast-conserving surgery plus radiotherapy (BCT+RT) resulted in significantly improved 10-year overall survival compared to mastectomy in early-stage breast cancer, with adjusted hazard ratio of 0.81 (95% CI 0.78-0.85, p<0.0001). 1

Study Design and Population

• This was a large population-based study from the Netherlands Cancer Registry including 37,207 women diagnosed with primary invasive stage T1-2, N0-1, M0 breast cancer between 2000-2004 1
• 21,734 patients (58%) received BCT+RT while 15,473 (42%) underwent mastectomy 1
• A representative subcohort of 7,552 patients diagnosed in 2003 was analyzed for breast cancer-specific outcomes 1

Primary Survival Outcomes

Overall Survival

• Unadjusted 10-year overall survival showed dramatic improvement with BCT+RT (HR 0.51,95% CI 0.49-0.53, p<0.0001) 1
• After adjusting for confounding variables including tumor characteristics and patient factors, BCT+RT still demonstrated superior overall survival (adjusted HR 0.81,95% CI 0.78-0.85, p<0.0001) 1
• This survival benefit remained significant across all T and N stage subgroups 1

Breast Cancer-Specific Survival

• BCT+RT significantly improved 10-year relative survival (a measure of breast cancer-specific mortality) in the overall cohort (adjusted HR 0.76,95% CI 0.64-0.91, p=0.003) 1
• The T1N0 subgroup showed particularly strong benefit (adjusted HR 0.60,95% CI 0.42-0.85, p=0.004) 1

Distant Metastasis-Free Survival

• BCT+RT did not significantly improve 10-year distant metastasis-free survival in the overall cohort (adjusted HR 0.88,95% CI 0.77-1.01, p=0.07) 1
• However, the T1N0 subgroup did show significant improvement (adjusted HR 0.74,95% CI 0.58-0.94, p=0.014) 1

Clinical Interpretation

Confounding by Severity

• The lack of improvement in distant metastasis-free survival in the overall cohort, despite improved overall and relative survival, suggests possible confounding by disease severity 1
• Patients selected for mastectomy may have had more aggressive disease features not fully captured by TNM staging alone 1

Equivalence at Minimum

• These results demonstrate that BCT+RT is at least equivalent to mastectomy for overall survival and may actually be superior in appropriately selected patients 1
• This finding aligns with other major randomized trials showing equivalence between BCT+RT and mastectomy 2

Context Within Breast Cancer Treatment Guidelines

Supporting Evidence from Other Trials

• The NSABP B-06 trial with 20-year follow-up showed no survival differences between mastectomy, lumpectomy alone, or lumpectomy plus radiation (HR for BCT+RT vs mastectomy: 0.97,95% CI 0.83-1.14, p=0.74) 2
• The National Cancer Institute trial with 25-year follow-up similarly showed equivalent overall survival (43.8% for mastectomy vs 37.9% for BCT, p=0.38) 3

Current Guideline Recommendations

• Multiple guidelines now recognize BCT+RT as equivalent to mastectomy for early-stage breast cancer (Category 1 recommendation) 4
• The choice between BCT+RT and mastectomy should be based on patient preference, tumor characteristics, and ability to achieve negative margins 4

Clinical Implications

The Dutch trial provides the strongest population-based evidence that BCT+RT should be considered the preferred approach for early-stage breast cancer when technically feasible, as it offers at least equivalent and possibly superior survival outcomes compared to mastectomy. 1