Targeted Therapy Success Rates: — What the Numbers Really Mean

Response rate measures how often a tumour shrank by a defined amount during treatment. Survival — usually reported as progression-free survival or overall survival — measures time: how long before the cancer grew again, or how long patients lived. A drug can have a high response rate with a short duration of benefit, or a modest response rate with durable, long-lasting control. Both figures matter, and asking your oncologist to explain both gives you a fuller picture than either number alone.

No, and this is one of the most common misunderstandings. A trial response rate describes what happened in a specific group — with particular mutations, stages, and treatment histories. You may resemble that group closely, or differ from it in ways that shift the figure significantly. What your oncologist can tell you is whether your profile matches the patients who responded in that trial, and where that puts you relative to the overall result.

Progression-free survival is the length of time that passed, on average, before the cancer started growing again in trial patients. It is often the figure used to compare targeted therapies against each other because it reflects how long the treatment kept the cancer in check. It does not tell you how long you will live. When progression happens, it usually means the cancer has found a way around the drug, which leads to a treatment review — not the end of options.

Different trials enrol different patient populations, use different definitions of response, and measure results at different timepoints. A trial run in one region or ethnic group may show a different response rate from a trial elsewhere, because underlying mutation frequencies and treatment histories differ. When you compare figures from different sources, you are often comparing different populations — which explains much of the variation. Your oncologist can tell you which figure applies most closely to your situation.

Not necessarily. The right question is what the alternative is. A treatment with a modest response rate may still be the best available option if the alternatives show lower rates, more severe side effects, or less durable responses for your particular cancer. Your oncologist weighs the response rate against every available option, not against an ideal. A single figure in isolation does not answer whether a treatment is worth it — the comparison does.

Resistance developing over time is a common and expected part of targeted therapy, not a personal failure. Most targeted therapies work for a period and then stop as the cancer adapts — this is why progression-free survival is reported alongside response rate in every major trial. When resistance appears, your oncologist will assess what has changed, sometimes ordering repeat biopsy or molecular testing, and will discuss whether a different targeted drug or a different treatment type is the best next step.

Targeted therapy trials select patients who carry a specific mutation or marker. Chemotherapy trials typically enrol broader populations. Comparing the two response rates without accounting for this difference is misleading — the populations are different by design. For patients who carry the relevant mutation, ASCO and ESMO guidance consistently shows that targeted therapies achieve higher response rates in those selected populations than conventional chemotherapy. For patients who lack the target, that advantage does not hold.

For some cancers — particularly rarer subtypes — the evidence base for targeted therapy is early, built on small trials, or not yet established. If your oncologist is recommending a targeted therapy in this setting, ask them to explain what the evidence consists of and how confident they are in applying it to your situation. It is entirely reasonable to ask for a second opinion or for referral to a multidisciplinary tumour board that regularly reviews cases like yours. 'We do not yet have robust data' is a legitimate and honest answer.