Oligoprogression: — When Only One or Two Spots Grow

There is no universally agreed number, and it varies between cancer types and between clinical trials. Many studies and guidelines use one to three or one to five progressing sites as a working definition. What matters in practice is whether local treatment of all progressing sites is technically feasible while systemic therapy continues. Your oncologist's assessment depends on the total picture — the number of sites, their location, and whether treating all of them locally is clinically reasonable.

It is most commonly described in patients on targeted therapy or immunotherapy, where treatment is highly effective at controlling most of the disease but a small resistant clone escapes. It is also seen with hormone therapy in prostate and breast cancers. It is less often used as a framework in chemotherapy, where resistance more commonly involves broader disease escape rather than isolated sites.

In many cases, no — and avoiding an unnecessary treatment change is exactly the aim of the oligoprogression approach. If local treatment successfully eliminates the resistant site, your current systemic therapy often continues unchanged. Whether to pause or switch depends on the treatment type, how many sites are involved, and what the biopsy reveals about the resistance mechanism. Your oncologist will weigh the risk of continuing against the benefit of not abandoning an otherwise effective therapy.

Not every site is accessible for local treatment, and in that situation your oncologist will consider switching your systemic therapy rather than attempting ablation. A biopsy of the progressing site, where safely possible, helps identify which next-line treatment is most likely to work for that resistance mechanism. A clinical trial is also worth discussing, particularly if the molecular change driving resistance has been identified and a relevant study exists.

Not always, but it is often recommended because the molecular changes driving resistance can directly guide what comes next. A biopsy finding a specific resistance mutation may point to a targeted agent that addresses it. Where a tumour biopsy cannot be done safely, a liquid biopsy — a blood test for circulating tumour DNA — is sometimes used instead, though it does not detect every resistance change clearly. Your oncologist can explain what is appropriate in your specific situation.

This depends on how fast the resistant site is growing and whether it is causing symptoms. A slowly growing spot not pressing on any critical structure may allow time for full planning of local treatment. A site causing pain, affecting function, or pressing on a critical structure needs faster attention. Your oncologist will prioritise based on the location, rate of growth, and your overall condition — and that conversation should happen at your next appointment rather than being delayed.