DÄ internationalArchive22/2010Resistance Tests Were Not Mentioned
LNSLNS Clinical practice guidelines for the treatment of a disease assume that disease course does not vary much. However, this is not the case for advanced colorectal cancer (CCRC). The demand for individualized chemotherapy is based on the fact that malignant tumors can escape the growth inhibiting effect of medications by means of numerous complex and individually varying mechanisms and thus become resistant to treatment.

In the clinical practice guidelines for colorectal cancer, which include recommendations for the drug treatment of cancers that have reached advanced stages, no mention is made of possibilities of diagnosing tumor resistance. It is not understandable that resistance tests are not mentioned in the guidelines. The development of resistance tests started in the 1960s, and after initial setbacks, such tests have greatly improved in terms of accuracy. The accuracy of the tests for diagnosing resistance with cell cultures taken from fresh tumor tissue can meanwhile exceed 90% (1, 2). Monitoring cancer drug resistance by means of positron emission tomography (PET scanning) constitutes another great step forward, since it enables doctors to identify not only very small tumor foci but also metabolic changes, and thus resistance (3).

The currently promoted individualized cancer treatments apply to subgroups of patients who are selectively chosen on the basis of biomarker measurement and receive specific treatment. Experience to date has shown, however, that subgroup therapy cannot replace resistance tests.

Guidelines are of great clinical importance, because—as for colorectal cancer—they inform doctors about the latest therapeutic options. However, in the context of drug treatment of CRC, it should not be overlooked that these days measuring tumor resistance provides a means of saving patients from ineffective treatments.
DOI: 10.3238/arztebl.2010.0399a


Prof. Dr. med. Theodor H. Lippert
Medizinische Fakultät der Universität Tübingen
Erlenweg 38
72076 Tübingen, Germany
Theodor-Lippert@web.de

Conflict of interest statement
The author declares that no conflict of interest exists according to the guidelines of the International Committee of Medical Journal Editors.
1.
Lippert TH, et al.: Intrinsic and acquired drug resistance in malignant tumors. The main reason for therapeutic failure. Arzneimittel-Forschung (Drug Research) 2008; 58: 261–4. MEDLINE
2.
Blumenthal RD: Chemosensitivity, Volume 1, In Vitro Assays. Totowa, New Jersey: Humana Press 2005.
3.
Lippert TH, et al.: Resistenzprobleme bei der medikamentösen Krebsbehandlung: II. Testung von Tumorresistenzen. Gyne 2009; 30: 28–33.
4.
Schmiegel W, Pox C, Arnold D, Porschen R, Rödel C, Reinacker-Schick A: Clinical practice guideline: Colorectal carcinoma — The managment of polyps, (neo)adjuvant therapie, and the treatment of metastases [Klinische Leitlinie Kolorektales Karzinom – Polypenmanagement, (neo)adjuvante Therapie, Therapie im metastasierten Stadium]. Dtsch Arztebl Int 2009; 106 (51–52): 843–8. VOLLTEXT
1. Lippert TH, et al.: Intrinsic and acquired drug resistance in malignant tumors. The main reason for therapeutic failure. Arzneimittel-Forschung (Drug Research) 2008; 58: 261–4. MEDLINE
2. Blumenthal RD: Chemosensitivity, Volume 1, In Vitro Assays. Totowa, New Jersey: Humana Press 2005.
3. Lippert TH, et al.: Resistenzprobleme bei der medikamentösen Krebsbehandlung: II. Testung von Tumorresistenzen. Gyne 2009; 30: 28–33.
4. Schmiegel W, Pox C, Arnold D, Porschen R, Rödel C, Reinacker-Schick A: Clinical practice guideline: Colorectal carcinoma — The managment of polyps, (neo)adjuvant therapie, and the treatment of metastases [Klinische Leitlinie Kolorektales Karzinom – Polypenmanagement, (neo)adjuvante Therapie, Therapie im metastasierten Stadium]. Dtsch Arztebl Int 2009; 106 (51–52): 843–8. VOLLTEXT