Complete response
All detectable signs of the tumour have vanished on scans and examination after treatment. The best result a trial can record for an individual patient, though microscopic disease may remain.
Under RECIST, complete response means every target lesion has disappeared and any lymph nodes have shrunk below 10 mm; it must be confirmed on a repeat scan. Complete responses are common in lymphomas and germ-cell tumours and were historically rare in solid tumours, so their appearance with immunotherapy and cell therapy (around 20% in metastatic melanoma with ipilimumab plus nivolumab, most of them lasting) was a genuine change. Pathologic complete response is the surgical equivalent: no cancer cells found in the removed tissue after pre-operative treatment.