Inclusion Criteria:  Voluntary informed consent. Aged at least 18 years. Diagnosis of locally advanced or metastatic RCC, Melanoma or NSCLC In the opinion of the investigator deemed suitable to receive first-line combination immunotherapy (RCC and MM) or combination immunotherapy and chemotherapy (NSCLC). Willingness to comply with scheduled trial procedures. Capable of performing own dry blood sampling procedure, or a carer who is willing and able to perform them.  Exclusion Criteria:  Previous immunotherapy (including any CPI either as single agent on in combination, or high dose interleukin-2). Judgement by the investigator that the individual should not participate if they are unlikely to comply with study procedures and requirements. Patients receiving long term oral anticoagulation deemed by the clinician to be at risk from daily finger pricking.