When cancer spreads beyond its original site, it enters a metastatic stage, typically treated with systemic therapies like chemotherapy. These treatments aim to control the disease throughout the body, often shifting the goal from cure to long-term management. This systemic approach faces a challenge when a patient’s widespread disease remains stable, but a few isolated tumor sites begin to grow despite the ongoing treatment. This specific scenario of limited, isolated progression requires a specialized approach increasingly recognized in modern oncology.
Defining Oligoprogression
Oligoprogression describes a situation where a patient with established metastatic cancer, currently receiving systemic treatment, experiences growth in only a small, limited number of existing tumor sites. The term combines the prefix “oligo” (few) with “progression” (tumor growth). This pattern typically involves the growth of one to five lesions, while the majority of other metastatic sites remain controlled, stable, or shrinking due to the current systemic drug regimen.
This state differs from widespread systemic progression, which involves numerous tumors growing simultaneously and requires switching treatment. It is also distinct from oligometastasis, where a patient presents with only a few metastases initially, before systemic treatment begins. Oligoprogression is a manifestation of tumor heterogeneity: a few specific cancer cell clones develop resistance to the current drug, while the rest of the cancer remains sensitive. This partial resistance means the systemic therapy is still providing benefit to the patient, making the management strategy unique.
Identifying Progressive Lesions
Identifying oligoprogression relies heavily on regular surveillance using advanced medical imaging. Patients on systemic therapy undergo routine scans to monitor all known tumor sites and detect new disease. Modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans pinpoint the location and measure the size of suspicious lesions.
Measuring these few lesions over time confirms true progression. Clinicians use standardized criteria to determine if a lesion has grown enough to be classified as progressive, ensuring minor fluctuations are not mistaken for significant advancement. Sometimes, a biopsy of the growing tumor is performed to understand underlying biological changes. This tissue analysis can reveal specific genetic mutations or resistance mechanisms that allowed that particular tumor site to escape the systemic drug’s effects.
Targeted Treatment Strategies
The management strategy for oligoprogression focuses on eliminating the few resistant tumor sites while preserving the ongoing effective systemic treatment. This approach, often called local ablative therapy (LAT) or metastasis-directed therapy, aims to avoid switching to a new systemic therapy, which would expose the patient to potential new side effects and risks.
Stereotactic Body Radiation Therapy (SBRT), also known as Stereotactic Ablative Radiotherapy (SABR), is a common local treatment. SBRT delivers high doses of precisely focused radiation to the small, growing tumors over a limited number of sessions, often resulting in high local control rates. Other local methods include radiofrequency ablation (RFA), which uses heat generated by electrical currents to destroy the tumor, and surgical resection, which physically removes the progressive lesion.
Applying these localized treatments destroys the resistant tumor clones, allowing the patient to remain on the systemic therapy that is successfully controlling all other disease sites. This strategy can effectively “reset the clock” on progression. The selective removal of these resistant lesions delays the need for a change in therapy, which is particularly beneficial if the next available systemic drug has a higher burden of side effects.
Prognosis and Clinical Significance
The identification and targeted treatment of oligoprogression represent a significant shift toward personalized cancer management, often leading to a more favorable outlook. Data from multiple studies, including the randomized phase II CURB trial, indicate that patients who receive local therapy for oligoprogression while continuing their systemic treatment experience extended progression-free survival compared to those who only switch systemic therapies. Specifically, this combined approach has been shown to prolong the time until the disease progresses again by several months in some patient populations.
Treating oligoprogression allows patients to stay on the effective systemic drug for a longer duration, sometimes extending the overall time on the initial therapy by over a year. The ability to delay the introduction of subsequent, often more toxic, lines of therapy translates directly into a better quality of life. In selected cases, particularly in non-small cell lung cancer, the median overall survival for patients treated with local ablation has been substantially longer compared to those who immediately switch systemic therapy. This evidence supports managing oligoprogression aggressively and locally to achieve prolonged disease control.