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Role of Repeat PET/CT Scans in Ensuring Accuracy of Staging of Locally Advanced NSCLC


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Findings from a new study highlight the importance of timing in initial staging positron-emission tomography (PET) and/or computed tomography (CT) scans for patients with locally advanced non–small cell lung cancer (NSCLC) receiving chemoradiation therapy.1

According to data presented at the 2019 Multidisciplinary Thoracic Cancers Symposium, 35% of patients had changes in management based on a repeat PET/CT performed at a median of 35 days after an initial scan. The results of the phase II study showed that upstaging to stage IV disease occurred in 10% of patients, and 25% of patients had significant changes in nodal staging and treatment volume that affected their radiation field design.

Jing Zeng, MD

Jing Zeng, MD

“Based on these data, current practice guidelines as well as insurance coverage policy should consider the cost-effectiveness of short-term repeat imaging scans to ensure we’re accurately staging and treating our patients,” said lead author of the study, Jing Zeng, MD, Associate Professor of Radiation Oncology at University of Washington School of Medicine, Seattle.

Why Repeat Scans Are Important

As Dr. Zeng explained, PET/CT is a standard-of-care tool used in the staging of NSCLC; it improves the detection of both mediastinal lymph node metastases and distant metastatic disease relative to CT scans. Nevertheless, she said, insurance companies have been reluctant to cover repeat PET/CTs for newly diagnosed patients with cancer. In 2010, the Centers for Medicare & Medicaid Services (CMS) updated its National Coverage Determinations Manual to remove the absolute frequency limitation of one PET scan. CMS will continue to nationally cover one PET scan related to the initial treatment strategy, whereas local Medicare administrative contractors will have the discretion to cover (or not) any additional PET scans as part of initial treatment.

Repeat PET/CT in Locally Advanced Lung Cancer

  • For patients with locally advanced NSCLC planned for definitive chemoradiation therapy, a repeat PET/CT performed at a median of 35 days after an initial scan led to 10% of patients being upstaged to stage IV disease.
  • An additional 25% of patients had significant changes in nodal staging and treatment volume with repeat PET/CT scans.
  • For more on the therapeutic implications of proper disease staging in non–small cell lung cancer, see an interview with Jing Zeng, MD, on The ASCO Post Newsreels at www.ascopost.com/videos.

According to Dr. Zeng, the importance of repeat PET/CT scans has been demonstrated in prior studies. A systematic review of 35 publications analyzing the use of PET/CT for radiation treatment planning showed that a repeat PET/CT scan after initial staging led to a 20% change in treatment intent to palliation and a 36% change in target definition.2

For this study, as part of the phase II FLARE-RT trial, Dr. Zeng and colleagues performed a repeat PET/CT scan for radiation treatment planning if a prior scan had not been performed within 4 weeks. Of the 20 patients who required a repeat PET/CT, there was a median of 35 days between initial and repeat scans. Despite the few days between scans, said Dr. Zeng, 10% of patients (n = 2) were found to have metastatic disease and an additional 25% (n = 5) had increased nodal involvement, increasing the size of their radiation fields.

Predicting Changes in Management?

Dr. Zeng and colleagues next tried to see whether the likelihood of upstaging could be predicted prior to performing the repeat PET/CT scan. Despite the small number of patients analyzed, the investigators observed a general trend with respect to standardized uptake values (SUVs). In patients who were upstaged, there was a higher SUVmax, SUVmean, and SUVpeak, as well as larger metabolic tumor volume and total lesion glycolysis, compared with patients whose staging remained the same.

“Not surprisingly, we found that bigger, more 18F-fluorodeoxyglucose–avid tumors were more likely to be upstaged on a repeat PET scan,” said Dr. Zeng. “Those are probably the tumors we need to be most concerned about to make sure we’re accurately staging.”

According to Dr. Zeng, these results mirror findings from a 2014 study of 47 treatment-naive patients with NSCLC; it showed that more than half of patients experienced upstaging in tumor, nodal stage, or metastatic rate.3 For a subset of patients who underwent both scans on the same instrument, SUV velocity predicted upstaging. 

DISCLOSURE: Dr. Zeng reported no conflicts of interest.

REFERENCES

1. Zeng J: Upstaging in repeat PET/CT prior to chemoradiation in locally advanced NSCLC: Implications for clinical care. 2019 Multidisciplinary Thoracic Cancers Symposium. Abstract 2. Presented March 14, 2019.

2. Hallqvist A, Alverbratt C, Strandell A, et al: Positron emission tomography and computed tomographic imaging (PET/CT) for dose planning purposes of thoracic radiation with curative intent in lung cancer patients: A systematic review and meta-analysis. Radiother Oncol 123:71-77, 2017.

3. Geiger GA, Kim MB, Xanthopoulos EP, et al: Stage migration in planning PET/CT scans in patients due to receive radiotherapy for non-small-cell lung cancer. Clin Lung Cancer 15:79-85, 2014.


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