Contribution of Multicenter Expertise and Deformable Fusion Software for Re-irradiations With Curative Intent

Recent clinical data confirm the possibility and clinical benefit of delivering a second irradiation with curative intent even if the commonly accepted maximum doses to OARs had been reached during the first irradiation.

However, there is no consensus on acceptable doses to AORs in a re-irradiation context. The difficulty of making decisions and validating dosimetry may limit access to treatment. Re-irradiations are therefore carried out according to local experience and equipment, resulting in territorial inequality.

MiM software is an innovative software dedicated to images registration and dose summation. It allows the EQD2 doses of the various irradiations to be cumulated.

Recruitment and inclusion step: For each included patient (signed consent form), the center provides an initial opinion concerning the indication for re-irradiation with curative intent (Opinion 1).

Indication and pre-dosimetric study step:

• If re-irradiation with curative intent Is not feasible according to the center: timages of the 1st irradiation and recent diagnosis images will be sent to Centre Léon Bérard (CLB), merged into MIM by physicists, and the indication is discussed in a multidisciplinary meeting (Opinion 2).
• If re-irradiation with curative intent is feasible according to the center: CT + RT structures+doses of 1st irradiation and dosimetric scan of the 2nd irradiation will be sent to CLB, merged into MIM. Multidisciplinary meeting will deliver the Opinion 3 with dosimetric instructions for the new irradiation, in particular OARs doses constraints.

Study withdrawal if the indication for re-irradiation is not validated.

Cumulative doses validation step:

CT + RT structures+doses of the planned re-irradiation will be sent to CLB and EQD2 doses will be summed into MIM. If cumulative doses are accepted by consensus, multidisciplinary meeting will deliver the Opinion 4. Otherwise the center will have to do a new planimetry.

Patients for whom re-irradiation with curative intent has been declared possible will be followed for 2 years according to standard practices, approximately every 3 months and analyzed for tolerance and efficiency.

Inclusion criteria

• Age ≥ 18 years when signing the consent form
• Re-irradiation with desired curative intent (≥ 50 Gy EQD2), with volume to be irradiated totally or partially included in a previous irradiation field:

• Oligo-metastases or oligo-progression (< 5 metastases in less than 3 sites)
• Second non-metastatic cancer
• Isolated local recurrence
• Life expectancy > 6 months
• Dated and signed informed consent
• Affiliation to a social security scheme or equivalent

Exclusion criteria

• Indication of intracranial, prostate, rectum or esophagus re-irradiation
• Diagnosis of multi-metastatic cancer
• PS ECOG ≥ 2
• Impossibility to interrupt current treatment with a tyrosine kinase inhibitor or other systemic treatment (excluding hormonal therapy) which may potentiate the rays effects (duration of wash-out according to treatment instructions)
• Pregnant or breastfeeding women
• Tutorship or curatorship or deprivation of liberty