PET/MR imaging of pelvic malignancies

Pediatric Imaging Using PET/MR Imaging

PET/MR imaging is a one-stop shop technique for pediatric diseases allowing not only an accurate clinical assessment of tumors at staging and restaging but also the diagnosis of neurologic, inflammatory, and infectious diseases in complex cases. Moreover, applying PET kinetic analyses and sequences such as diffusion-weighted imaging as well as quantitative analysis investigating the relationship between disease metabolic activity and cellularity can be applied. Complex radiomics analysis can also be performed.

Clinical impact of PET/MRI in oligometastatic colorectal cancer

BACKGROUND

Oligometastatic colorectal cancer (CRC) is potentially curable and demands individualised strategies.

METHODS

This single-centre retrospective study investigated if positron emission tomography (PET)/magnetic resonance imaging (MR) had a clinical impact on oligometastatic CRC relative to the standard of care imaging (SCI). Adult patients with oligometastatic CRC on SCI who also underwent PET/MR between 3/2016 and 3/2019 were included. The exclusion criterion was lack of confirmatory standard of reference, either surgical pathology, intraoperative gross confirmation or imaging follow-up. SCI consisted of contrast-enhanced (CE) computed tomography (CT) of the chest/abdomen/pelvis, abdominal/pelvic CE-MR, and/or CE whole-body PET/CT with diagnostic quality (i.e. standard radiation dose) CT. Follow-up was evaluated until 3/2020.

RESULTS

Thirty-one patients constituted the cohort, 16 (52%) male, median patient age was 53 years (interquartile range: 49-65 years). PET/MR and SCI results were divergent in 19% (95% CI 9-37%) of the cases, with PET/MR leading to management changes in all of them. The diagnostic accuracy of PET/MR was 90 ± 5%, versus 71 ± 8% for SCI. In a pairwise analysis, PET/MR outperformed SCI when compared to the reference standard (p = 0.0412).

CONCLUSIONS

These findings suggest the potential usefulness of PET/MR in the management of oligometastatic CRC.

[Lymph node management in endometrial cancer]

In 2018, around 382,100 new cases of endometrial cancer (EC) were reported worldwide, accounting for about 4.4% of all new cases of cancer in women. In France, in 2018, the EC is the first gynecological cancer in incidence and the fourth cancer in women. The rationale for the therapeutic management of EC is based on the estimation of a theoretical risk of recurrence and lymph node metastasis using MRI and preoperative biopsy criteria. However, lymph node status remains the determining factor of adjuvant treatment. In order to reduce the morbidity of lymphadenectomy, the concept of sentinel lymph node biopsy (SLN) has been developed. The SLN technique has evolved in recent years, thanks to the advent of robotics and the creation of fluorescence detection cameras. It has been shown that detection of SLN with Indocyanine Green (ICG) allows for more frequent bilateral migration of 88 to 100% and better detection of pelvic GS in 97% of cases with a decrease in morbidity. Recently, in view of the absence of a therapeutic role of lymph node staging, the operational risks and the delay of adjuvant treatments, in case of pelvic lymph node metastasis on definitive histological examination, the question of secondarily performing paraaortic lymphadenectomy arises. The SLN procedure, extended to all early-stage endometrial cancers, should lead to a major reduction in the use of secondary staging and better adaptation of adjuvant therapy.

Clinical impact of PET/MR in treated colorectal cancer patients

PURPOSE

The primary aim of the present study was to evaluate if PET/MR induced management changes versus standard of care imaging (SCI) in treated colorectal cancer patients. The secondary aim was to assess the staging performance of PET/MR and of SCI versus the final oncologic stage.

METHODS

Treated CRC patients who underwent PET/MR with ¹⁸F-FDG and SCI between January 2016 and October 2018 were enrolled in this retrospective study. Their medical records were evaluated to ascertain if PET/MR had impacted on their clinical management versus SCI. The final oncologic stage, as reported in the electronic medical record, was considered the true stage of disease.

RESULTS

A total of 39 patients who underwent 42 PET/MR studies were included, mean age 56.7 years (range 39-75 years), 26 males, and 13 females. PET/MR changed clinical management 15/42 times (35.7%, standard error ± 7.4%); these 15 changes in management were due to upstaging in 9/42 (21.5%) and downstaging in 6/42 (14.2%). The differences in management prompted by SCI versus PET/MR were statistically significant, and PET/MR outperformed SCI (P value < 0.001; odds ratio = 2.8). In relation to the secondary outcome, PET/MR outperformed the SCI in accuracy of oncologic staging (P value = 0.016; odds ratio = 4.6).

CONCLUSIONS

PET/MR is a promising imaging tool in the evaluation of treated CRC and might change the management in these patients. However, multicenter prospective studies with larger patient samples are required in order to confirm these preliminary results.

Technical and instrumentational foundations of PET/MRI

This paper highlights the origins of combined positron emission tomography (PET) and magnetic resonance imaging (MRI) whole-body systems that were first introduced for applications in humans in 2010. This text first covers basic aspects of each imaging modality before describing the technical and methodological challenges of combining PET and MRI within a single system. After several years of development, combined and even fully-integrated PET/MRI systems have become available and made their way into the clinic. This multi-modality imaging system lends itself to the advanced exploration of diseases to support personalized medicine in a long run. To that extent, this paper provides an introduction to PET/MRI methodology and important technical solutions.