Radiation Oncology/Breast/Occult

Occult Breast Primary

Guidelines

• NCCN Guideline (v2.2010)
  • Mammogram and axillary ultrasound
  • Chest/abdomen/pelvic CT
  • Breast MRI:
    • If MRI+, then follow stage-appropriate pathway
    • If MRI-, T0N1
      • Mastectomy + ANLD
      • ALND + WBRT +/- nodal irradiation
      • Chemotherapy as per N1 guidelines
    • If MRI-, T0N2-3, then neoadjuvant chemotherapy, followed by mastectomy + ALND as per locally advanced guideline (presumably including PMRT)

Overview

• Rare presentation (<1%)
• Breast MRI may be positive in as many as 60-70% of mammogram/ultrasound negative patients
  • There is limited information on outcomes of patients who are MRI-
• Omiting local therapy (mastectomy or RT) results in poor outcomes, with local failure >70% and significantly worse OS
• Local therapy with mastectomy or ALND + RT appears equivalent
• 5-year LRR ranges between 10% and 58% in retrospective studies

Breast MRI

• Orbis Medical Centre, The Netherlands; 2010 PMID 19822403 -- "Breast MRI in clinically and mammographically occult breast cancer presenting with an axillary metastasis: a systematic review." (de Bresser J, Eur J Surg Oncol. 2010 Feb;36(2):114-9. Epub 2009 Oct 12.)
  • Systematic review. 8 retrospective studies.
  • Outcome: Breast MRI can detect otherwise occult cancer in >2/3 patients; high sensitivity but low specificity. In 80% of such patients, lesions can again be found with U/S for biopsy
  • Conclusion: Breast MRI can result in additional detection of otherwise occult lesions. Because of low specificity, lesions should be histologically confirmed

Breast Conservation Therapy

• SEER/MD Anderson; 2010 (1983-2006) PMID 20564117 -- "Population-based analysis of occult primary breast cancer with axillary lymph node metastasis." (Walker GV, Cancer. 2010 Jun 8. [Epub ahead of print])
  • SEER analysis, 750 patients with T0 N+ M0 disease (incidence 0.1%). ALND 80%, mastectomy 37%, RT 45%, neither mastectomy/RT 29%. Observation only 12%. Majority of patients pre-MRI era. Median F/U 4 years
  • Outcome: 4-year OS 73%, CSS 83%. 10-year OS if BCT/Mastectomy 65% vs ALND only 58% vs observation 47% (SS). If ALND, no difference in 10-year OS between mastectomy 63% and BCT 76% (NS). MVA predictors for poor CSS: ER-, ≥ 10 LN+, <10 LN resected. Over time, increasing use of BCT and decreasing use of mastectomy.
  • Conclusion: Need locoregional therapy; BCT with ALND and RT appears to provide equivalent outcomes to mastectomy