R classification
The R-classification is a facet classification from medicine and describes a characteristic classification of malignant tumors ( cancer ).
The letter "R" stands as an abbreviation for "residual" (Latin residuus: remaining). The absence or presence of residual tumor after therapy is described by the R classification:
- RX The presence of residual tumor cannot be assessed
- R0 No residual tumor
- R1 Microscopic residual tumor
- R2 Macroscopic residual tumor
- R2a Macroscopic residual tumor, not confirmed microscopically
- R2b Macroscopic residual tumor, confirmed microscopically
The R classification has two facets. It was originally designed as a prognostic factor for overall survival after therapy and is also described as such in the TNM system. Any remaining tumor after therapy must be taken into account.
If, for example, the patient has a liver metastasis, but initially only the primary tumor (with lymph nodes) was completely removed during the operation, according to this definition, an R2 situation exists despite tumor-free incision margins.
However, since the pathologist examining a surgical specimen can only assess what he sees, he will still select R0 as the result in this case. Given that this is a prognostic factor for the recurrence of a local recurrence, this is also necessary.
Therefore, according to the current recommendation of the TNM system, it must always be stated what the "R" refers to so that the information can be treated correctly in evaluations.
Incidentally, an R0 specification is also possible if no tumor can be detected after systemic and radiation therapy and in compliance with certain rules, e.g. For example, if a tumor that was originally resected locally R1 is no longer indicative of residuals after the post-irradiation treatment with biopsy and / or imaging procedures.
