European Radiology: The value of PET/CT in evaluating the effectiveness of radiotherapy in patients with metastatic nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a common malignancy with nearly 130,000 new cases worldwide each year, endemic in southern China, with most cases linked
to EBV infection.
About 10% of newly diagnosed nasopharyngeal carcinomas are new-onset metastatic nasopharyngeal carcinomas (mNPCs), with a poor
clinical prognosis.

Clinically, patient response to palliative chemotherapy (PCT) is the most important prognostic factor
.
Final radiotherapy (DRT) of the nasopharynx and neck may greatly improve the survival outcomes of those patients with nasopharyngeal carcinoma who are satisfied with the PCT response.

Therefore, in daily clinical work, local treatment decisions
are mainly made based on the patient's response to PCT.
However, mNPC responses after PCT are usually determined by computed tomography (CT) and/or magnetic resonance imaging (MRI).

However, these modalities reflect only morphological and anatomical changes in the primary tumor and distant metastasis sites, and therefore have limited
ability to assess response to treatment.

In addition, it is difficult to assess the site
of bone metastases with CT or MRI scans.
Functional imaging methods, such as PET/CT (positron emission tomography/computed tomography) imaging, have great advantages
in detecting treatment response and recurrence.

However, although most NPCs are poorly differentiated squamous cell carcinomas that show high uptake of 2-deoxy-2-[18F]fluoro-D-glucose (2-[18F]FDG on 2-[18F]FDG PET/CT imaging, PET/CT imaging has not been widely used for post-treatment evaluation
of mNPCs.
In PET/CT imaging, the use of standardized uptake values (SUVs) is the most important factor
in quantifying PET data and assessing glucose metabolism in lesions.
The Deauville score is based on metabolic activity in the tumor relative to the mediastinal blood pool and liver, is reproducible, and has good predictive power
compared to non-standard visual examination.
However, the prognostic significance of the Deauville score regarding mNPCs has not been adequately addressed
.

In addition to post-PCT reactions, EBV DNA has also been studied as an important factor
in guiding DRT in patients with mNPC.
Plasma EBV DNA has been recognized as the most important biomarker of NPC risk and an effective method
for tumor surveillance after treatment.
However, to date, no studies have focused on the use
of the above combinations in mNPC risk classification or to guide DRT in mNPC patients.

Recently, a study published in the journal European Radiology identified the patients with mNPC who may benefit from receiving DRT by evaluating the Deauville score and EBV DNA after PCT, providing a reference for the development of personalized clinical treatment plans
.

A total of 570 patients
with mNPC treated with PCT or PCT+DRT were included in this study.
Risk stratification was performed based on recursive zoning analysis (RPA), EBV DNA levels, and post-PCT Deauville scores.


There was a clear difference in survival between patients with Deauville scores of 1-3 and 4-5 (2-year progression-free survival (PFS): 23.
4% vs 8.
5%, P < 0.
001; 2-year overall survival (OS): 56.
8%) vs18.
8%, P < 0.
001).

RPA produced three distinct groups, with increased risk sequentially (Deauville scores for all RPA I-II were in the 1-3 range).

(1) RPA I: EBV DNA level concentration before treatment ≤ 4000 copies/ml, and undetectable after PCT;

(2) RPA II: EBV DN level pre-treatment concentration > 4000 copies/ml or pre-treatment concentration ≤4000 copies/ml, and detectable after PCT;

(3) RPA III: Deauville score 4-5.

Although patients with RPA I and RPA II had significantly higher PFS rates when treated with PCT+DRT than when treated with PCT alone (RPA I: 72.
7% vs.
13.
4%, RPA II: 37.
8% vs.
6.
3%), patients with RPA III did not have this PFS advantage (6.
5% vs.
9.
7%)
.

 Figure Kaplan-Meier survival estimates vary
with treatment modality and RPA stratification.
PCT, palliative chemotherapy; DRT, definitive radiotherapy

This study shows that the Deauville score is appropriate for risk classification
in patients with mNPC.
In addition, using the Deauville score, this study constructed a new, RPA-based model that classifies patients with mNPC into three risk tiers
.
While DRT confers a clear prognostic advantage (in terms of improving PFS and OS rates) for patients in the low- and intermediate-risk tiers, this benefit does not extend to patients in the high-risk tier

Original source:

Zhen-Chong Yang,Ying-Ying Hu,Li-Ting Liu,et al.
Determining the suitability of definitive radiation therapy in patients with metastatic nasopharyngeal carcinoma based on PET/CT: a large cohort study.
DOI:10.
1007/s00330-022-08814-3