How do doctors know if cancer treatment is working?
Oncologists evaluate the efficacy of antitumour therapy using several parallel clinical methods and standardised endpoints. Monitoring treatment response is based on changes in tumour size or metabolic activity, duration of survival and progression, tumour-specific biomarkers, as well as patient-reported clinical outcomes.
1. Imaging studies and structured response criteria: During systemic therapies or radiotherapy, regular imaging studies (such as CT, MRI, or PET-CT) are performed. International criteria systems (such as RECIST for solid tumours, or specific immuno-oncology criteria) are applied to measure lesion dimensions. Based on changes in tumour size, complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD) are determined.
2. Histopathological response: In preoperative (neoadjuvant) treatments, histopathological examination of the specimen removed following surgery is used to assess whether viable tumour cells remain (pathological complete response or residual disease).
3. Clinical endpoints: The primary indicators of treatment efficacy are progression-free survival (PFS – the length of time the tumour does not grow) and overall survival (OS).
4. Biomarkers and functional measurements: In certain tumour types, changes in the levels of blood-based tumour markers or molecular markers also indicate disease activity.
5. Clinical symptoms and quality of life (PRO): Treating physicians also consider the patient's general performance status, physical functioning, quality of life, and symptom relief when assessing efficacy.