An easy-to-use phantom and protocol for weekly PET quality assessment: a multicenter study

Monitoring tumour response during chemo-radiotherapy: a parametric method using FDG-PET/CT images in patients with oesophageal cancer

Background

The objective of this study is to investigate the feasibility and the additional interest of a parametric imaging (PI) method to monitor the early tumour metabolic response in a prospective series of oesophageal cancer patients who underwent positron emission tomography with fluoro-2-deoxy-d-glucose (FDG-PET/CT) before and during curative-intent chemo-radiotherapy.

Methods

Fifty-seven patients with squamous cell carcinoma (SCC) of the oesophagus prospectively underwent FDG-PET/CT before chemo-radiotherapy (CRT) (PET₁) and at 21 ± 3 days after the beginning of CRT (PET₂). The outcome was assessed at 3 months and 1 year after the completion of CRT (clinical examination, CT scan or FDG-PET/CT, biopsy). For each patient, PET₁ and PET₂ were registered using CT images. The 2 PET image sets were subtracted, so the voxels with significant changes in FDG uptake were identified. A model-based analysis of this graph was used to identify the tumour voxels in which significant changes occurred between the two scans and yielded indices characterising these changes (green and red clusters). Quantitative parameters were compared with clinical outcome at 3 months and at 1 year.

Results

The baseline tumour FDG uptake decreased significantly at PET₂ (p < 0.0001). The tumour volume significantly decreased between PET₁ and PET₂ (p < 0.02). The initial functional volume of the lesion (TV₁) was significantly lower (p < 0.02) in patients in clinical response (CR) at 3 months and 1 year. The volume of the lesion during the treatment (TV₂) was significantly lower in patients identified as in CR at 3 months (p < 0.03), but did not predict the outcome at 1 year. Multivariate analyses of outcome at 3 months showed that the risk of failure/death increased with younger age (p = 0.001), larger metabolic volume on PET₁ (p = 0.009) and larger volume with decreased FDG uptake (p = 0.047). As for outcome at 1 year, the risk of failure/death increased with younger age (p = 0.006), nodal involvement (p = 0.08) and larger volumes with increased uptake (p = 0.03).

Conclusion

A parametric method to assess tumour response on serial FDG-PET performed during chemo-radiotherapy was evaluated. Early metabolic changes, i.e. variations in FDG uptake, provided additional prognostic information in multivariate analyses ClinicalTrials.gov NCT 00934505.

Trial registration

Current Controlled Trials ISRCTN7824458

FDG PET during radiochemotherapy is predictive of outcome at 1 year in non-small-cell lung cancer patients: a prospective multicentre study (RTEP2)

PURPOSE

To assess prospectively the prognostic value of FDG PET/CT during curative-intent radiotherapy (RT) with or without concomitant chemotherapy in patients with non-small-cell lung cancer (NSCLC).

METHODS

Patients with histological proof of invasive localized NSCLC and evaluable tumour, and who were candidates for curative-intent radiochemotherapy (RCT) or RT were preincluded after providing written informed consent. Definitive inclusion was conditional upon significant FDG uptake before RT (PET₁). All included patients had a FDG PET/CT scan during RT (PET₂, mean dose 43 Gy) and were evaluated by FDG PET/CT at 3 months and 1 year after RT. The main endpoint was death (from whatever cause) or tumour progression at 1 year.

RESULTS

Of 77 patients preincluded, 52 were evaluable. Among the evaluable patients, 77% received RT with induction chemotherapy and 73% RT with concomitant chemotherapy. At 1 year, 40 patients (77 %) had died or had tumour progression. No statistically significant association was found between stage (IIIB vs. other), histology (squamous cell carcinoma vs. other), induction or concomitant chemotherapy, and death/tumour progression at 1 year. The SUVmax in the PET2 scan was the single variable predictive of death or tumour progression at 1 year (odds ratio 1.97, 95% CI 1.25 - 3.09, p = 0.003) in multivariate analysis. The area under the receiver operating characteristic curve was 0.85 (95% CI 0.73 - 0.94, p < 10(-4)). A SUVmax value of 5.3 in the PET₂ scan yielded a sensitivity of 70% and a specificity of 92% for predicting tumour progression or death at 1 year.

CONCLUSION

This prospective multicentre study demonstrated the prognostic value in terms of disease-free survival of SUVmax assessed during the 5th week of curative-intent RT or RCT in NSCLC patients (NCT01261598; RTEP2 study).

The predictive value of treatment response using FDG PET performed on day 21 of chemoradiotherapy in patients with oesophageal squamous cell carcinoma. A prospective, multicentre study (RTEP3)

PURPOSE

FDG PET has been suggested to have predictive value in the prognosis of oesophageal carcinoma. However, the retrospective studies reported in the literature have shown discordant results. Additionally, only four studies have evaluated FDG PET during chemoradiotherapy (CRT) in patients with different histological lesions. The purpose of this study was to investigate the predictive value of FDG PET performed early during CRT (on day 21) in a population of patients with oesophageal squamous cell carcinoma.

METHODS

Included in this prospective study were 57 patients with a histological diagnosis of squamous cell carcinoma of the oesophagus. Of these 57 patients, 48 (84%) were evaluated (aged 63 ± 11 years; 44 men, 4 women). Each patient underwent FDG PET (4.5 MBq/kg) before CRT, according to the Herskovic protocol (t0; PET₁) and on day 21 ± 3 from the start of CRT (d21; PET₂). The response assessment included a clinical examination, CT scan or FDG PET and histological analysis 3 months and 1 year after PET₁. The patients were classified as showing a complete response (CR) or a noncomplete response. A quantitative analysis was carried out for PET₁ and PET₂ using the following parameters: SUVmax, SUVmean (with SUVmean40 as the 3-D volume at an SUVmax threshold of 40% and SUVmeanp as that defined by a physician), tumour volume (TV, with TV40 defined as the TV at 40% of SUVmax, and TVp as that defined by a physician); and the total lesion glycolysis (TLG, SUVmean × TV, with TLG₄₀ defined as the TLG at 40% of SUVmax, and TLGp as that defined by a physician). The differences in responses at 3 months and 1 year between PET₁ (t0) and PET₂ (d21) were assessed in terms of variations in SUV, TV and TLG using a repeated measures of variance (ANOVA).

RESULTS

SUVmax, SUVmean and TLG decreased significantly between PET₁ (t0) and PET₂ (d21; p < 0.0001). The TV significantly decreased only when assessed as TVp (p = 0.02); TV₄₀ did not decrease significantly. With respect to the predictive value of PET₁, only TV40_1 and TVp_1 values, and therefore TLG40_1 and TLGp_1, but not the SUV values, were significantly lower in patients with CR at 3 months. SUVmax1, TVp_1 and TLGp_1 were significantly lower in patients with CR at 1 year. With respect to the predictive value of PET₂, only TV40_2 and TVp_2 values, and therefore TLG40_2 and TLGp_2, but not the SUV values, were significantly lower in patients with CR at 3 months. None of the PET₂ parameters had significant value in predicting patient outcome at 1 year. The changes in SUVmax, TV₄₀, TVp, TLG₄₀ and TLGp between PET₁ and PET₂ had no relationship to patient outcome at 3 months or 1 year.

CONCLUSION

This prospective, multicentre study performed in a selected population of patients with oesophageal squamous cell cancer demonstrates that the parameters derived from baseline PET₁ are good predictors of response to CRT. Specifically, a high TV and TLG are associated with a poor response to CRT at 3 months and 1 year, and a high SUVmax is associated with a poor response to CRT at 1 year. FDG PET performed during CRT on day 21 appears to have less clinical relevance. However, patients with a large functional TV on day 21 of CRT have a poor clinical outcome (ClinicalTrials.gov NCT 00934505).

A new method for volume segmentation of PET images, based on possibility theory

18F-fluorodeoxyglucose positron emission tomography (18FDG PET) has become an essential technique in oncology. Accurate segmentation and uptake quantification are crucial in order to enable objective follow-up, the optimization of radiotherapy planning, and therapeutic evaluation. We have designed and evaluated a new, nearly automatic and operator-independent segmentation approach. This incorporated possibility theory, in order to take into account the uncertainty and inaccuracy inherent in the image. The approach remained independent of PET facilities since it did not require any preliminary calibration. Good results were obtained from phantom images [percent error =18.38% (mean) ± 9.72% (standard deviation)]. Results on simulated and anatomopathological data sets were quantified using different similarity measures and showed the method was efficient (simulated images: Dice index =82.18% ± 13.53% for SUV =2.5 ). The approach could, therefore, be an efficient and robust tool for uptake volume segmentation, and lead to new indicators for measuring volume of interest activity.

Design and construction of a quality control phantom for SPECT and PET imaging

In this article, the authors present a method for quickly and easily constructing test phantoms for PET and SPECT quality assurance. As a demonstration, they constructed a complex prototype test phantom, showing the strengths of the construction method. Images taken using a PET/CT and a SPECT scanner are presented, along with a qualitative evaluation of PET/CT using the test phantom. The construction technique provides a quick, easy, and cost effective means of constructing a phantom for use in nuclear medicine imaging.