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PET - The great progress in cancer diagnosis

One of the most important requirements in the treatment of diseases is diagnosis, that is, the precise description of a disease using all medical knowledge and opportunities. Medical practice makes use of different methods.

A milestone in looking at the human body "without a scalpel" was the discovery of X-rays by Wilhelm Conrad Röntgen, who received the Nobel Prize for it in 1901.

Modern tumour diagnosis consists of different, complementary methods:

  • endoscopic examination methods, that is, looking into body cavities and hollow organs, often associated with the removal of tissue (biopsy)
  • biochemical study of retrieved tissue in respect of benign and malignant status, tumour type, etc.
  • imaging techniques such as X-rays, ultrasound, computer tomography (CT), magnetic resonance imaging (MRI) or PET.

Positron emission tomography (PET) is one of the most modern and most accurate examination methods of tumour diagnosis. It has been used since the late 80s, especially in brain studies and is now regarded as the most important diagnostic tool in the search for a variety of tumours. Pure PET gives relatively blurred images which makes the location of tumours complicated. Combining PET with CT (so-called PET / CT) combines the advantages of both methods.

Here is an interview excerpt from the magazine "Zur Gesundheit" [About Health] with the Cologne nuclear physician Dr. Eveline Korman who has been involved with PET for years.

Zur Gesundheit (ZG) : How is PET different from CT and MRI?

Dr. Eveline Korman (EK): With this examination technique we can determine whether a tumour is malignant and distinguish between scars and active cancer tissue. So we can determine whether the cancer is still alive in a non-invasive way (that is, without opening the body). An advantage of PET is that the whole body is looked at in one examination, ie, we detect possible metastasis (secondary tumours).

ZG: Where is PET used?

EK : In recent years the applications have been defined by leading nuclear medicine specialists and clinicians in Germany based on consensus conferences and classified into different categories according to internationally approved classification methods. The highest level is called "1a" -indication. The pancreas, the lymph glands and the thyroid and black skin cancer (melanoma) and pulmonary nodules in high-risk patients belong in his category.

ZG : How does PET provide such accurate test results without a knife?

EK : Let's consider the lung. Here PET spares the patient the rigours of a general anesthetic and surgery. This results in considerable cost savings. PET uses the fact that cancer tumours have a significantly higher rate of metabolism than healthy tissue and therefore convert more glucose (sugar). We inject a special slightly radioactive tracer into the patient’s arm vein one hour before the examination, a sugar solution, called F-18 FDG. After this substance is absorbed in the tumour tissue, the marked sugar is not broken down, but stored and the tumour becomes more recognisable. The affected tissue can then be located accurately and clearly. Thus it is usually possible to say whether it is a benign or malignant tumour.

ZG : The result of your test results is then therapy in the form of surgery, radiation, or the familar chemotherapy. Can PET help from there onwards?

EK : Yes. After treatment, PET can show whether it was effective and should be continued or if the treatment needs to be changed.

ZG : Will the health insurance companies pay for the costs?

EK : Patients with a private health insurance can use the procedure because PET has been recognised and established since 1995 in the medical fees schedule (fees regulations for doctors). Patients who are members of one of the public health insurance companies in Germany need special approval. The decision to accept the costs is up to the health insurance company concerned, and the companies usually adhere in turn to the recommendations of the medical service of the public health insurances. At present, discretionary individual decisions are made that can be favourable towards the so-called "1a-indication" (see above). I have often pointed out with some regret that this is not dealt with consistently nationwide. But I hope that it will be possible in future for insured patients and their doctors to use PET more frequently to get a more accurate diagnosis and thus be able to choose the optimal treatment.

ZG : Dr. Korman, thank you for the interview!