PET for oncological applications

PET for oncological applications

 

  1. The main objectives of PET imaging
    1. Initial cancer staging
    2. Evalation of the response to treatment
    3. Evaluation of cancer recurrence
    4. Prognostic importance in treatment

 

  1. Oncological indications for 18F-FDG PET scans
    1. Lung cancer
      • Assessment of a single lung tumor (size > 1 cm) diagnosed on the basis of CT or chest X-ray - sensitivity / specificity of 97% / 78%
      • Cancer staging (concerns mostly non-small cell lung cancer), especially in patients with normal-sized mediastinal nodes (<1cm) in CT (CT criteria for diagnosing metastases to lymph nodes are nodes > 1cm which equals to the sensitivity of 45% in detection of metastases; PET scan sensitivity equals to 80-90%)
      • Cancer recurrence detection
    2. Mesothelioma
      • Differentiating the benign and malignant tumors (metastases from lungs, breasts, ovaries, prostate, kidneys, sarcoma, neo pleural primary tumor) through the evaluation of the level of FDG metabolism
      • Indicating the optimal spot for biopsy of the pleura with indication of proliferative process by showing the most active proliferative hyperplastic tissue
    3. Colorectal cancer
      • Cancer staging (mostly distant metastases, especially to the liver) immediately after the initial pathologic diagnosis
      • Evaluation of possible recurrence in the event of an increase of CEA marker or ambiguous imaging results
    4. Hodgkin's lymphoma (HL) and non-Hodgkin lymphoma (NHL)
      • Cancer staging before treatment (the scan has higher sensitivity than CT and MRI, especially if the disease has spread to the bone marrow)
      • Early (after 1-3 chemotherapy cycles) evaluation of the response to treatment. This procedure allows for the differentiation of residual disease from active proliferative process
      • Cancer recurrence detection
    5. Breast cancer
      • Evaluation of multifocal cancer and assessment of the possible recurrence in patients with "dense" nipple
      • Cancer staging in patients with suspected disseminated malignancy before treatment
      • Evaluation of the response to chemotherapeutic treatment or detection of a possible local recurrence or distant metastases in patients in which other imaging techniques were not sufficient
    6. Head and neck cancer
      • Diagnosis of metastases to cervical lymph nodes (especially for normal sized lymph nodes <1cm) and distant metastases
      • Assessment of the response to radiotherapy and chemotherapy
      • Evaluation of cancer recurrence (2-3 months after treatment taking into consideration the presence of increased FDG uptake in the post-operative and post-radiation changes)
      • Radiotherapy planning with precise determination of the irradiated volume
    7. Thyroid cancer
      • Evaluaton of a possible cancer recurrence in a patient with elevated thyroglobulin levels and with negative result of iodine whole-body scintigraphy
      • Monitoring the treatment of medullary thyroid cancer with persistent increased calcitonin levels in serum, in case of normal scintigraphy image with the use of 99mTc-Tektreotyd
    8. Reproductive system cancers
    9. Cervical cancer
      • Evaluation of local lymph nodes in patients with cervical cancer initial diagnosis; evaluation of the response to treatment; detection of recurrences
    10. Endometrial cancer
      • Evaluation of local lymph nodes and organs in the abdomen, as well as detection of recurrences
      • Limited value in the initial assessment of the depth of myometrial invasion
      • False-positive results - uterine fibroids and ovaries in the peri-ovulatory phase
    11. Ovarian cancer
      • Cancer staging and detection of recurrences in case of Ca-125 level increase (importance of the knowledge of the menstrual cycle because of the physiological increase of FDG levels in the peri-ovulatory phase) 
    12. Testicular cancer
      • Detection of distant metastases
      • Cancer staging and recurrence evaluation (exception-mature teratoma)
    13. Sarcomas
      • Cancer staging (in some types of sarcomas the sensitivity is higher than in scintigraphy with MDP-Tc99m)
      • Evalation of the response to treatment (after 1-3 cycles of chemotherapy)
    14. Melanoma
      • Diagnosis of distant metastases (however, the evaluation of local lymph nodes has a high specificity but low sensitivity, therefore the sentinel lymph node mapping method using gamma-cameras followed by a histopathological examination is better)
      • Cancer recurrence evaluation
    15. Esophageal cancer
      • Early detection of esophageal cancer
      • Evaluation of the treatment effectiveness and possible recurrence
    16. Other types of gastrointestinal cancer
      • Initial differential diagnosis of abnormal changes in the pancreas and the liver (high sensitivity and specificity of the scan, particularly when using the PET-MRI scanner)
    17. Neuroendocrine tumors
      • Cancer staging and recurrence evaluation of undifferentiated neuroendocrine tumors before treatment and with normal scintigraphy images with 131I/123I-MIBG or 99mTc-oktreotyd/68Ga-DOTATOC/18F-FDOPA
    18. CNS malignant tumors
      • Assessment of histological malignancy of the tumor
      • Prognosis - high level of FDG accumulation in the tumor does not constitute a good prognosis
      • Planning a brain tumor biopsy - identifying the most hypermetabolic (malignant) part of the tumor
      • Differentiation between the necrotic mass with the remaining part of the tumor, for example after surgery and radiotherapy
      • Monitoring the response to treatment and recurrence evaluation after treatment

 

  1. Other radiolabels used in PET scan that are also applicable in oncological diagnostics
    1. 11C- Methionine, 18F-Tyrosine (FET)- these radiolabels are characterized by low accumulation in the brain and inflamed tissue
      • Differentiation between the tumor living tissue and post-operative and post-radiation necrosis
      • Evaluation of the size and spread of glioma in order to determine the stage or to evaluate the recurrence (especially in well-differentiated gliomas with low FDG uptake)
      • Localization of parathyroid tumors (adenoma and carcinoma)
    2. 11C- Choline, 18F- Choline and 11C-acetate
      • Cancer staging in prostate cancer, especially with ambiguous results from other imaging methods
      • Cancer recurrence evaluation in case of sudden PSA level increase
      • Qualification for liver transplant or other radical treatment in patients with liver cancer
    3. 68Ga-PSMA- membrane antigen of prostate cancer cells
      • Prostate cancer diagnostics (has better sensitivity in detecting metastases than the method using 11C-Choline)
    4. 68Ga- DOTATOC / DOTATATE
      • Staging and recurrence evaluation of neuroendocrine tumors
      • Evalation of the response to treatment
    5. 18F-FluoroDOPA
      • Neuroendocrine tumors (especially carcinoid tumor) diagnostics
      • Congenital hyperinsulinism diagnostics
      • Glioma and Parkinson's disease diagnostics
    6. 124I-MIBG
      • Pheochromocytoma, neuroblastoma, ganglioneuroma, carcinoid and medullary thyroid cancer diagnostics
    7. 18FNa
      • Diagnostics of benign and malignant bone diseases (higher sensitivity and shorter waiting period after administering the radiolabel in comparison with the method using 99mTc-MDP; 15-30min after 18FNa and 2-3h after 99mTc-MDP
    8. 18F-FLT (fluorothymidine) - cellular proliferation marker 
      • Also accumulates in inflammatory changes
      • Evalation of the response to treatment (earlier than in case of FDG)
      • Detecting of lung and CNS tumors, differentiation of gliomas with low and high malignancy levels
    9. 124I-cG250- an antibody directed towards the carbonic anhydrase IX antigen overexpressed in clear cell cancer
      • Pre-identification of the type of renal tumor
    10. 18F-MISO (fluoromisonidazole); 62Cu-ATSM (nitroimidazole compound)
      • evaluation of the oxygen concentration in tumors (hypoxia results in resistance to radiation and certain types of chemotherapy)
    11. 18F-florbetapir (Amyvid)/ 18F-florbetaben/ 18F-flutemetamol
      • Used in brain imaging to determine the presence of large quantities of beta-amyloid plaques observed in patients suffering from various types of dementia ( Alzheimer's disease, dementia with Lewy bodies, dementia associated with Parkinson's disease)
      • A negative result showing a small amount of amyloid plaques indicates a low probability for the patient to be suffering from Alzheimer’s desease
      • A positive result is not sufficient for the diagnosis of Alzheimer's disease, as in other dementias can also show large amounts of amyloid plaques
    12. 18F16α-17β-fluoroestradiol (FES)- diagnostics of expression of estrogen receptors
      • Prognosis of response to endocrine therapy in breast cancer