JNM: PET/CT, SPECT/CT integral in cancer treatment planning
Pretherapeutic axial 68Ga-DOTATATE PET (A) and CT (B) slices, compared with posttherapeutic 68Ga-DOTATATE PET (C) and CT (D) slices, showing abdominal lymph node metastasis. Image source: SNM

A series of studies published in the September issue of the Journal of Nuclear Medicine show that molecular imaging plays a critical role in the evaluation and treatment planning for a spectrum of cancers, including thyroid cancer, neuroendocrine tumors, Hodgkin lymphoma and non-small cell lung cancer.

In the first study, Ravinder Grewal, MD, an assistant attending physician in nuclear medicine at Memorial Sloan-Kettering Cancer Center in New York City, and colleagues performed planar imaging and SPECT/CT on 148 patients with thyroid cancer. The results showed that SPECT/CT provided information that reduced the need for additional cross-sectional imaging in 29 patients and redefined the initial risk of recurrence estimates in seven of 109 postsurgical patients, thereby altering patient management recommendations in terms of frequency and intensity of follow-up studies.

“For patients with thyroid cancer, ‘one size fits all’ no longer applies,” said Grewal. “Through molecular imaging, the paradigm is changing toward more tailored and customized management of treatment. As a result, we can see how far a disease has spread and spare the patient from additional examination, time and radiation exposure,” Grewal added.

In another study, researchers from Germany used PET/CT with the radiotracer 68Ga-DOTATATE to evaluate the effectiveness of molecular imaging in monitoring patients with neuroendocrine tumors after undergoing peptide receptor radionuclide treatment (PRRT). The study evaluated 33 patients at baseline and three months after treatment began. Decreased 68Ga-DOTATATE uptake in tumors after the first cycle of PRRT predicted time to progression and correlated with an improvement in clinical symptoms among patients with well differentiated neuroendocrine tumors.

“This molecular imaging technique can help doctors to classify patients according to their prognosis and to choose a personalized follow-up strategy,” said study co-author Alexander Haug, MD, a researcher at Ludwig-Maximilians-University in Munich. “With the use of specific biomarkers, nuclear medicine provides the unique opportunity to perform diagnosis and therapy with the same tracer compound and—with the use of different biomarkers—to provide personalized tissue characterization. Nuclear medicine will be essential for the work-up of cancer patients in the near future.”

The third study also used molecular imaging to monitor treatment success and aid in planning. Researchers from Brazil evaluated 104 patients with newly diagnosed Hodgkin lymphoma using FDG PET after undergoing two cycles of chemotherapy treatment. Of these patients, 93 achieved complete remission after first-line therapy. During a median follow-up of 36 months, relapse or disease progression was seen in 22 patients. Researchers found that PET is an accurate and independent predictor of event-free survival in Hodgkin lymphoma patients.

“Our findings suggest that early interim FDG PET may play a pivotal role in Hodgkin lymphoma treatment, tailoring the therapy to an individual level, providing a less toxic treatment for patients with a low risk of failure while attempting treatment intensification for patients regarded as high risk of failure on the basis of the PET findings,” said Juliano Cerci, MD, from the division of nuclear medicine, at the Medical School of the University of São Paulo in Brazil, and corresponding author of the study.

The fourth study investigated the role of 18F-FDG PET/CT for the early identification of response to therapy in patients with non-small cell lung cancer (NSCLC). Houke M. Klomp, MD, from the department of surgery, the Netherlands Cancer Institute–Antoni van Leeuwenhoek Hospital, Amsterdam and colleagues studied 23 NSCLC patients who were treated with a molecular-targeted agent called epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) and used 18F-FDG PET/CT to monitor the disease before and at one week after administration of EGFR-TKI.

Changes in tumor 18F-FDG uptake during treatment were measured by standardized uptake values. Six patients experienced partial response, while 16 patients had stable disease and one patient had progressive disease. The results of the study suggested that early during the course of therapy, 18F-FDG PET/CT can predict response to treatment in patients with NSCLC.

Even though the study was relatively small, the results are promising and consistent with the results of preclinical studies, according to Komp and collegues. Further data in larger groups of patients are required to determine the optimal timing of response evaluation and the relevance of cut-off values of response parameters, Komp and colleagues concluded.