Inclusion Criteria:
* Age \>= 18 years.
* Histologically confirmed extracranial solid tumor (primary, locally recurrent or metastatic) that is advanced or unresectable (technically unresectable, medically inoperable, without a remaining standard curative surgical option, or with curative treatment at disproportionate cost such as loss of an entire organ or major function, as documented by a multidisciplinary team), or that has active disease after standard therapy and for which standard local treatment is assessed as unsuitable.
* At least 1 and no more than 10 target lesions at entry. A target lesion is a non-intracranial lesion, visible on imaging, that can be safely reached by ultrasound- or CT-guided percutaneous puncture or injected under direct vision. Not every visible lesion has to be injectable. Non-target lesions may be present and are recorded. Where safe and feasible, all safely reachable visible lesions are listed as target lesions.
* Contrast-enhanced CT (with ultrasound or MRI where needed) completed before entry, establishing the inventory of all visible lesions and of target lesions with their volumes. PET-CT is encouraged but not required.
* Every target lesion \<= 10 cm in greatest dimension.
* ECOG performance status \<= 2; life expectancy \>= 3 months.
* Platelet count \>= 50 x 10\^9/L and INR \<= 1.5. Anticoagulant and antiplatelet therapy is withheld or bridged as for image-guided percutaneous puncture.
* Estimated glomerular filtration rate (eGFR) \>= 30 mL/min/1.73 m².
* Able to understand the study and give written informed consent.
* Subjects of reproductive potential, and male subjects with partners of reproductive potential, agree to use effective contraception from consent until 3 months after the last session.
Exclusion Criteria:
* No lesion that can be safely punctured or injected under direct vision, or the lesion(s) to be treated encase major vessels or nerves such that the risk of access is unacceptable.
* Severe coagulopathy or high bleeding risk.
* Uncontrolled serious infection, systemic decompensation, severe cachexia or multi-organ failure.
* Pregnancy or lactation.
* Psychiatric or cognitive impairment preventing cooperation.
* Intracranial tumor or intracranial metastasis.
* Rapidly progressive, widespread disease for which local treatment of target lesions is assessed by the MDT as having no clinical value.
* Contraindication to the procedures or medications required by this protocol without an alternative (e.g., inability to tolerate puncture under local anesthesia with intravenous analgesia).
* Candidate for curative treatment that can be delivered with low morbidity.
* Hypersensitivity to iodinated contrast or uncontrolled hyperthyroidism, where a lesion requires CT guidance. Such a lesion may be treated under ultrasound guidance only.
* Any other condition rendering the subject unsuitable in the investigator's judgment.