Radiation Therapy to the Breast in Krukenberg Tumors
Radiation therapy to the breast has no role in the treatment of Krukenberg tumors, as these are metastatic ovarian tumors that require systemic therapy and consideration of cytoreductive surgery, not locoregional breast radiation.
Understanding Krukenberg Tumors
Krukenberg tumors are metastatic ovarian malignancies characterized by mucin-secreting signet ring cells, representing approximately 30% of malignant ovarian neoplasms 1. The most common primary sites are:
- Stomach (most common, particularly linitis plastica) 2
- Colorectal cancer (52.4% in one series) 1
- Breast cancer (third most common) 1, 3
When breast cancer metastasizes to the ovary with signet ring cell features, it can meet the histologic criteria for Krukenberg tumor if signet ring cells comprise at least 10% of the tumor 3. These cases typically show bilateral ovarian involvement (87%) and occur in patients with invasive lobular carcinoma or invasive ductal carcinoma 3.
Why Breast Radiation Is Not Indicated
The presence of a Krukenberg tumor indicates stage IV metastatic disease, regardless of the primary site 1, 4. This fundamentally changes the treatment paradigm:
- Systemic disease requires systemic therapy, not locoregional treatment 1, 4
- Radiation to the breast would only address the primary site while ignoring widespread metastatic disease 1
- The median overall survival for Krukenberg tumors is only 14-29 months, reflecting the aggressive systemic nature of the disease 1, 2
Appropriate Treatment Approach for Krukenberg Tumors
Surgical Considerations
Cytoreductive surgery offers survival benefit when R0 resection can be achieved 1:
- Resection of both the primary tumor and Krukenberg tumor improves overall survival (hazard ratio 2.5) 1
- R0 resection provides the most significant survival advantage (hazard ratio 0.09) 1
- Median disease-free survival after R0 resection is 32 months 1
- Bilateral oophorectomy should be performed, as bilateral involvement occurs in 93% of cases 2
Prognostic Factors
Breast cancer as the primary site confers better overall survival compared to gastric or colorectal primaries (hazard ratio 0.31) 1. However, the presence of peritoneal or omental metastases predicts shorter disease-free survival even after successful R0 resection 1.
Role of Systemic Therapy
Chemotherapy is the mainstay of treatment for metastatic disease 2. However, historical series show limited appreciable effect from chemotherapy alone 2, emphasizing the importance of complete surgical resection when feasible 1.
Critical Pitfall to Avoid
Do not confuse the management of primary breast cancer with the management of breast cancer that has metastasized to the ovaries. The breast radiation guidelines provided in the evidence 5, 6 apply exclusively to locoregional treatment of early-stage breast cancer (stages I-III), not to stage IV metastatic disease with Krukenberg tumors. Applying locoregional radiation protocols to metastatic disease would be inappropriate and would not address the systemic nature of the malignancy 1, 4.