Rationale: Bladder tumours are often not visible on X-ray based image-modalities during planning and treatment of Radiotherapy.

Purpose: To determine if a single contrast (Lipiodol) demarcation of the bladder tumour before treatment is feasible and visible on multiple X-ray based image-modalities during Radiotherapy.

To exploit the potential of modern Radiotherapy (RT), it is important to localize and follow the target precisely during treatment. Since the bladder tumour can usually not be identified on conventional CT-scan, a fiducial or contrast marking system is warranted.

The iodized oil, Lipiodol is a well-known contrast media used mainly for lymphography and Hysterosalpingography. Local Lipiodol demarcation has been used for localisation of tumours in the lung, prostate and seminal vesicles visualised on Computed Tomography (CT) and fluoroscopy.

Purpose: To evaluate the feasibility of tumour demarcation using the contrast agent Lipiodol in adaptive Image-guided RT of bladder cancer. Visibility on CT, Cone-Beam CT, MRI and on-board imaging will be evaluated.

Inclusion Criteria:

• Histologically confirmed primary muscle invasive transitional cell carcinoma of the Bladder. T1-4a, N0-1, M0.
• Non-operable or refuse operation.
• Eligible for curative Radiotherapy.
• Oral and written informed consent.
• Fertile women must have a negative pregnancy test before inclusion or use contraceptive pills or intrauterine device.
• Ongoing beta blocker treatment is paused before Lipiodol injection.

Exclusion Criteria:

• Known metabolic disorder (hyperthyroidism, goiter)
• Allergy towards iodine.
• Pregnancy / breast-feeding
• Performance status ECOG > 2