the project was not started.

This study uses a novel unconventional radiotherapy technique, consisting of high dose PArtial Tumor irradiation targeting exclusively the HYpoxic segment of unresectable bulky tumors delivered either with photons (SBRT-PATHY) or with carbon-ions (CARBON-PATHY) while sparing the peritumoral immune microenvironment (PIM).

This study will be conducted as a two phase study. Phase A is a retrospective study. Up to 10 patients with bulky (>6cm tumors) previous planned with planning CT with IV contrast will be selected for planning and dosimetry comparison. This is performed to optimize the contouring and planning procedures. Phase B is a prospective study. Ten patients with bulky (>6cm tumor) requiring radiotherapy, with planning CT and MR with IV contrast will be accrued. Every effort will be made to include equal numbers of patients (2-3) from head and neck, thorax, abdomen and pelvis. Their images will be used for planning and dosimetry comparison.

Patients will be treated according to clinical plans. The study plans will not be used for treatment. Treatment plans for Photon delivery (SBRT-PATHY) and Carbon delivery (CARBON-PATHY) to deliver 30 Gy in three fractions will be planned to be delivered to the BTV will be performed. SBRT-PATHY plans will be generated at the Princess Margaret Cancer Center (PMCC, Toronto, Canada) while CARBON-PATHY plans will be generated at the MedAustron Center for Particle Therapy and Research (W. Neustadt, Austria).

The objective is to compare the dosimetric profile achievable using SBRT-PATHY (using photons) and CARBON-PATHY (using carbon-ions) for unresectable bulky tumors and surrounding tissues.

Inclusion Criteria:

1. Written informed consent (for use their planning CT and MR data for study specific planning)
2. Malignant solid bulky primary or recurrent tumor with diameter of ≥6 cm
3. Age > 18 years
4. Radiation planning CT (with IV contrast) and MRI (with or without IV contrast) is planned

Exclusion Criteria:

1. Patients without bulky lesions,
2. Contraindication to i.v. CT and MRT contrast medium administration, particularly estimated glomerular filtration rate (GFR) less than 45 mL/min/1.73 m².
3. Female patients who are pregnant, breast-feeding or male or female patients of reproductive potential who are not employing an effective method of birth control,
4. Any condition that, in the opinion of the investigators, would interfere with treatment planning or interpretation of study results

Note (1): criterion n°4 will be evaluated on the four eyes principle, evaluated by both Principle Investigator and Sub-Investigators.

Patients with unresectable bulky tumors (primary or metastatic) recommended to receive external beam radiotherapy, will be recruited from Princess Margaret Cancer Center and Medaustron. Every effort will be made to equal numbers (i.e. 2-3) from head and neck, thorax, abdomen, pelvis.