This is a single-centre, non-randomized, two-stage design, proof-of-concept study evaluating the radiolabelled PARP inhibitor [18F]-olaparib als potential tracer for imaging of tumour PARP expression by PET.

Inclusion Criteria:

1. Patients >18y, with biopsy-proven HPV-negative HNSCC, or patients >40y with HPV-positive HNSCC and high-risk features (i.e. > 10 smoke packs/year AND ≥N2b)
2. Treatment with chemoradiotherapy using platinum-based chemotherapy is anticipated
3. Recent archival tumour tissue (<8 weeks prior to inclusion) should be available with suffi-cient residual material for determination of tumour PARP1 levels
4. Presence of a tumour lesion ≥10 mm in diameter
5. ECOG performance status 0-2
6. Negative pregnancy test in women with childbearing potential
7. Life expectancy >3 months
8. Signed written informed consent and able to comply with the protocol
9. For stage II only: re-biopsy should be deemed feasible by the investigators (assessed by head-and-neck surgeon)

Exclusion Criteria:

1. Recent treatment with PARP inhibitors or other investigational therapies <30 days.
2. Presence of significant co-morbidities that make participation in the study undesirable according to the treating physician.