Advancements in Stage IV Breast Cancer Treatment: Targeting Oligometastasis and Oligoprogression

The landscape of stage IV breast cancer treatment is evolving, moving beyond the traditional view of widespread disease. A growing focus on identifying and treating “oligo-states”—oligometastatic and oligoprogressive disease—is offering new hope for patients. These conditions, characterized by progression in a limited number of sites (typically five or fewer), are being addressed with innovative strategies like metastasis-directed therapy (MDT).

Understanding Oligo-States

Traditionally, stage IV breast cancer was categorized as either localized or widespread. However, clinicians are now recognizing intermediate states where cancer has spread, but in a limited fashion. These “oligo-states” represent a significant opportunity for targeted intervention.

Oligometastatic Disease

Oligometastatic disease is defined as a distinct clinical entity between localized and widespread disease, typically involving 5 or fewer lesions.¹

Oligoprogressive Disease

Oligoprogressive disease refers to progression in a limited number of sites (approximately 1-5) after an initial positive response to systemic therapy.¹

The Role of Metastasis-Directed Therapy (MDT)

As systemic therapies improve, MDT is becoming a crucial tool for prolonging disease control. By specifically targeting lesions, clinicians aim to maintain the effectiveness of current systemic treatments and delay the need for more aggressive approaches.¹ Stereotactic ablative body radiotherapy (SABR) is a key example of MDT.

Clinical Trials and Emerging Data

AVATAR Trial

The phase 2 TROG 20.03 AVATAR trial assessed SABR for oligoprogressive, estrogen receptor-positive breast cancer. Results showed that 47% of patients (95% CI, 29%-63%) remained event-free for 6 months or more. The median progression-free survival was 9.9 months (95% CI, 4.1-not reached), suggesting SABR could be a viable alternative to CDK 4/6 inhibitor therapy.¹

Comet-5 Trial

The Comet-5 trial (NCT02933242) evaluated SABR in patients with up to 5 oligometastases. The rate of grade 3 or higher adverse events was relatively low, at 4.2% (95% CI, 2.2%-6.2%). At the 2-year Kaplan-Meier analysis, the rate of grade 2 or higher adverse events was 8% and grade 3 or higher events occurred in 4% of patients.¹

Radiosensitivity Considerations

Research indicates that lung metastases from breast cancer may have a lower radiosensitivity index compared to other histologies.¹ However, a recent trial did not indicate a need for significant dose deescalation.

Looking Ahead

The 43rd Annual Miami Breast Cancer Conference highlighted the growing importance of incorporating MDT into the treatment plans for patients with oligometastatic and oligoprogressive breast cancer. As research continues, a more personalized and targeted approach to stage IV breast cancer management is becoming a reality, offering the potential for improved disease control and quality of life.