Objective Radiological Response

Radiological Response Criteria in Oncology: An Overview

In the realm of oncology, assessing the response of tumors to treatment is pivotal. Various radiological criteria have been developed over the years to standardize and quantify tumor responses, facilitating consistent communication among clinicians and researchers. These criteria utilize imaging techniques to measure changes in tumor size, appearance, and metabolic activity, providing insights into the efficacy of therapeutic interventions.

  1. WHO Criteria: One of the earlier systems, it primarily focuses on the sum of the products of diameters (SPD) of tumors. A significant decrease or increase in SPD indicates a response or progression, respectively.

  2. RECIST 1.1: An evolution of the original RECIST, it emphasizes the sum of the longest diameters (SLD) of target lesions. It refines the definitions of measurable lesions and introduces specific guidelines for lymph nodes.

  3. Choi Criteria: Developed for gastrointestinal stromal tumors (GISTs), Choi combines changes in tumor size with changes in tumor density on computed tomography (CT).

  4. mRECIST: Modified RECIST, often used for hepatocellular carcinoma (HCC), emphasizes the “viable” portion of the tumor, which shows arterial phase enhancement on imaging.

  5. PERCIST: Focusing on metabolic activity, PERCIST uses 2-[fluorine 18]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) to assess changes in tumor metabolic activity, offering a different perspective from size-based criteria.

  6. Cheson Criteria: Tailored for lymphomas, this set of criteria considers not just tumor size but also metabolic activity using FDG-PET, and other specific features like spleen and liver size and bone marrow involvement.

  7. IrRC (Immune-related Response Criteria): Designed considering the unique response patterns seen with immunotherapies, IrRC incorporates the appearance of new lesions into its assessment.

These criteria, among others, offer tools to evaluate treatment responses, each with its strengths and specificities tailored to certain tumor types or treatment modalities. As oncology continues to evolve, so too will these criteria, adapting to new therapies and imaging techniques.

  • RECIST 1.0: Minimum size for measurable lesions = 10 mm at spiral CT, 20 mm at conventional CT. Method of measurement: Longest diameter.
  • Cheson: Used for lymphomas. Complete response also requires regression in spleen, liver, and clearance of bone marrow infiltrate.
  • IrRC (Immune-related Response Criteria): Designed for immunotherapies.
Criteria/ResponseWHORECIST 1.1mRECIST (for HCC)EASLRECIST 1.0ChoiPERCISTChesonIrRC (Immune-related Response Criteria)
Complete ResponseNo lesions detected for ≥4 weeksDisappearance of all target lesions and reduction of pathological lymph nodes to size <10 mmDisappearance of arterial phase enhancement in all target lesionsDisappearance of arterial phase enhancement in all target lesionsDisappearance of arterial phase enhancement in all target lesionsDisappearance of all target lesionsDisappearance of all metabolically active tumorsAll previously enlarged FDG-avid or PET-positive lesion and lymph nodes regressed to normal size (< 1.5 cm in greatest diameter)Disappearance of all lesions at two consecutive observations ≥4 weeks apart
Partial Response≥50% decrease in sum of all three diameter (confirmed at 4 weeks)≥30% decrease in sum of longest diameters of target lesions≥30% decrease in sum of longest diameters of “viable” target lesion (measurement to be done in arterial phase)≥50% decrease in sum of longest diameters of target lesions≥30% decrease in sum of longest diameters of target lesions≥10% decrease in tumor size or ≥15% decrease in tumor attenuation at CT>30% (0.8-unit) decline in SUL (lean body mass–normalized SUV [SUVlbm]) peak≥50% decrease in sum of the products of diameters of up to six largest dominant masses50% decrease in tumor burden (confirmed at 4 weeks)
Progressive Disease≥25% increase in sum of all three diameter; new lesions≥20% increase in sum of longest diameters and ≥5 mm absolute increase in diameter is required; new lesions≥20% increase in sum of longest diameters of “viable” target lesion (measurement to be done in arterial phase)≥25% increase in sum of longest diameters; new lesions≥20% increase in sum of longest diameters; new lesions≥10% increase in sum of longest diameters of lesions>30% (0.8-unit) increase in SUL peak, new lesion>50% increase in sum of the products of diameters of any previous lesions or appearance of one or more new lymph nodal lesions >1.5 cm (any axis)25% increase in tumor burden; new measurable lesions
Stable DiseaseNone of the aboveNone of the aboveNone of the aboveNone of the aboveNone of the aboveNone of the aboveNone of the aboveNone of the aboveNone of the above
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