PET/CT in therapy control

PET/CT with FDG as a metabolic marker improves the detection, staging, restaging und therapy monitoring in cancer diseases. FDG-PET/CT is a therapy controlling instrument in oncology. New radiopharmaceuticals allow for the visualization of the individual tumor biology. The combination of molecular imaging and in vitro markers already nowadays influences the planning of therapy.

The function-based PET/CT represents a suitable method for therapy control. Emphases are generated through statements about early therapy responses with the potential of dose reduction and the prognosis of long-term survival, as well as the supervision of radiotherapy with influence over the radiation field. Regarding the mentioned aspects, the use of PET/CT for treatment control includes in every case the medical potential of avoidance of under- or overtreatment as well as the economic potential of cost reduction, on the one side through the reduction of actual costs (eg. chemotherapy), and on the other side through avoiding medical follow-up costs as a consequence of under- or overtreatment.

"The classical radiological imaging reaches a crossroads. Modern tracers, which can attest molecular target structures, expand the achievements of the conventional imaging procedures, which solely can demonstrate anatomic changes. This can be well shown in the example of malignant illnesses. " R. Weißleder et al., Massachusetts General Hospital, Department of Radiology, Boston Radiologe. 2007; 47: 6-7.

When?

depending on the type of tumor and the selected therapy:

4 weeks after radiotherapy
4 weeks after radiotherapy
4-8 weeks after surgical procedure

Why?

Differentiation cicatrix necrosis

Optimisation of radiotherapy through identification of the vital residual tumor (opportunity to decrease the target volume)
Completion of a chemotherapy which is not required anymore (reduction of the risk of secondary tumors, especially in children)

Recognition of recurrence in patients without or with minor symptoms with elevated tumor markers

Punctual therapy of the recurrence

Differentiation resectable vs. non-resectable tumors (eg. NSCLC)

Reduction of the not indicated operation (eg. thoracotomies, see “Plus-Studie“)

Current Case Studies

Transaxial CT recording of a left side pulmonary round lesion

Curative Surgery enabled
PET/CT fusion image illustrates the left thoracic round lesion with considerably increased glucose metabolism

Change of therapy
In the CT tomogram, PET illustrates the typical malignant lymph node

Transaxial tomogram with display of a pulmonary tumor in segment 9 on the left and relatively distinctive pericardial effusion

Operation spared
Contralateral lymph node on the right side, mediastinal in the transaxial tomogram