Areas of high 18F-FDG uptake on preradiotherapy PET/CT identify preferential sites of local relapse after chemoradiotherapy for non-small cell lung cancer

18F-FDG-PET guided vs whole tumour radiotherapy dose escalation in patients with locally advanced non-small cell lung cancer (PET-Boost): Results from a randomised clinical trial

BACKGROUND AND PURPOSE

We aimed to assess if radiation dose escalation to either the whole primary tumour, or to an ¹⁸F-FDG-PET defined subvolume within the primary tumour known to be at high risk of local relapse, could improve local control in patients with locally advanced non-small-cell lung cancer.

MATERIALS AND METHODS

Patients with inoperable, stage II-III NSCLC were randomised (1:1) to receive dose-escalated radiotherapy to the whole primary tumour or a PET-defined subvolume, in 24 fractions. The primary endpoint was freedom from local failure (FFLF), assessed by central review of CT-imaging. A phase II 'pick-the-winner' design (alpha = 0.05; beta = 0.80) was applied to detect a 15 % increase in FFLF at 1-year.

CLINICALTRIALS

gov:NCT01024829.

RESULTS

150 patients were enrolled. 54 patients were randomised to the whole tumour group and 53 to the PET-subvolume group. The trial was closed early due to slow accrual. Median dose/fraction to the boosted volume was 3.30 Gy in the whole tumour group, and 3.50 Gy in the PET-subvolume group. The 1-year FFLF rate was 97 % (95 %CI 91-100) in whole tumour group, and 91 % (95 %CI 82-100) in the PET-subvolume group. Acute grade ≥ 3 adverse events occurred in 23 (43 %) and 20 (38 %) patients, and late grade ≥ 3 in 12 (22 %) and 17 (32 %), respectively. Grade 5 events occurred in 19 (18 %) patients in total, of which before disease progression in 4 (7 %) in the whole tumour group, and 5 (9 %) in the PET-subvolume group.

CONCLUSION

Both strategies met the primary objective to improve local control with 1-year rates. However, both strategies led to unexpected high rates of grade 5 toxicity. Dose differentiation, improved patient selection and better sparing of central structures are proposed to improve dose-escalation strategies.

[What dose escalation in the treatment of locally advanced non-small cell lung cancer?]

Despite significant therapeutic advances in the treatment of locally advanced inoperable non-small cell lung cancer (NSCLC), notably through adjuvant immunotherapy, the rate of therapeutic failure remains high. The use of positron emission tomography with fluorodeoxyglucose (FDG-PET), respiratory motion and intensity modulated radiotherapy (IMRT) have led to therapeutic improvements with reduced toxicity and better local control. The optimal dose to be delivered remains unknown due to discordant results of studies for almost 20 years and the way to define the area to benefit from a dose increase (whole volume, subvolume defined by pre- or per-radiotherapy PET).

Safety and efficacy of irradiation boost based on 18F-FET-PET in patients with newly diagnosed glioblastoma

PURPOSE

Dual timepoint FET-PET acquisition (10 and 60 minutes after FET injection) improves the definition of glioblastoma location and shape. Here we evaluated the safety and efficacy of simultaneous integrated boost (SIB) planned using dual FET-PET for postoperative glioblastoma treatment.

EXPERIMENTAL DESIGN

In this prospective pilot study (March 2017-December 2020), 17 patients qualified for FET-PET-based SIB intensity-modulated radiotherapy after resection. The prescribed dose was 78 and 60 Gy (2.6 and 2.0 Gy per fraction, respectively) for the FET-PET- and MR-based target volumes. Eleven patients had FET-PET within nine months to precisely define biological responses. Progression-free survival (PFS), overall survival (OS), toxicities, and radiation necrosis were evaluated. Six patients (35%) had tumors with MGMT promoter methylation.

RESULTS

The one- and two-year OS and PFS rates were 73% and 43% and 53% and 13%, respectively. The median OS and PFS were 24 (95%CI 9-26) and 12 (95%CI 6-18) months, respectively. Two patients developed uncontrolled seizures during radiotherapy and could not receive treatment per protocol. In patients treated per protocol, 7/15 presented with new or increased neurological deficits in the first month after irradiation. Radiation necrosis was diagnosed by MRI three months after SIB in five patients and later in another two patients. In two patients, the tumor was larger in FET-PET images after six months.

CONCLUSIONS

Survival outcomes using our novel dose escalation concept (total 78 Gy) were promising, even within the MGMTunmethylated subgroup. Excessive neurotoxicity was not observed, but radionecrosis was common and must be considered in future trials.

Comparison of Hypermetabolic and Hypoxic Volumes Delineated on [18F]FDG and [18F]Fluoromisonidazole PET/CT in Non-small-cell Lung Cancer Patients

PURPOSE

The high rates of failure in the radiotherapy target volume suggest that patients with stage II or III non-small-cell lung cancer (NSCLC) should receive an increased total dose of radiotherapy. 2-Deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) and [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO) (hypoxia) uptake on pre-radiotherapy positron emission tomography (PET)/X-ray computed tomography (CT) have been independently reported to identify intratumor subvolumes at higher risk of relapse after radiotherapy. We have compared the [¹⁸F]FDG and [¹⁸F]FMISO volumes defined by PET/CT in NSCLC patients included in a prospective study.

PROCEDURES

Thirty-four patients with non-resectable lung cancer underwent [¹⁸F]FDG and [¹⁸F]FMISO PET/CT before (pre-RT) and during radiotherapy (around 42 Gy, per-RT). The criteria were to delineate 40 % and 90 % SUVmax thresholds on [¹⁸F]FDG PET/CT (metabolic volumes), and SUV > 1.4 on pre-RT [¹⁸F]FMISO PET/CT (hypoxic volume). The functional volumes were delineated within the tumor volume as defined on co-registered CTs.

RESULTS

The mean pre-RT and per-RT [¹⁸F]FDG volumes were not statistically different (30.4 cc vs 22.2; P = 0.12). The mean pre-RT SUVmax [¹⁸F]FDG was higher than per-RT SUVmax (12.7 vs 6.5; P < 0.0001). The mean [¹⁸F]FMISO SUVmax and volumes were 2.7 and 1.37 cc, respectively. Volume-based analysis showed good overlap between [¹⁸F]FDG and [¹⁸F]FMISO for all methods of segmentation but a poor correlation for Jaccard or Dice Indices (DI). The DI maximum was 0.45 for a threshold at 40 or 50 %.

CONCLUSION

The correlation between [¹⁸F]FDG and [¹⁸F]FMISO uptake is low in NSCLC, making it possible to envisage different management strategies as the studies in progress show.

Evolutionary dynamics at the tumor edge reveal metabolic imaging biomarkers

Human cancers are biologically and morphologically heterogeneous. A variety of clonal populations emerge within these neoplasms and their interaction leads to complex spatiotemporal dynamics during tumor growth. We studied the reshaping of metabolic activity in human cancers by means of continuous and discrete mathematical models and matched the results to positron emission tomography (PET) imaging data. Our models revealed that the location of increasingly active proliferative cellular spots progressively drifted from the center of the tumor to the periphery, as a result of the competition between gradually more aggressive phenotypes. This computational finding led to the development of a metric, normalized distance from 18F-fluorodeoxyglucose (18F-FDG) hotspot to centroid (NHOC), based on the separation from the location of the activity (proliferation) hotspot to the tumor centroid. The NHOC metric can be computed for patients using 18F-FDG PET-computed tomography (PET/CT) images where the voxel of maximum uptake (standardized uptake value [SUV]max) is taken as the activity hotspot. Two datasets of 18F-FDG PET/CT images were collected, one from 61 breast cancer patients and another from 161 non-small-cell lung cancer patients. In both cohorts, survival analyses were carried out for the NHOC and for other classical PET/CT-based biomarkers, finding that the former had a high prognostic value, outperforming the latter. In summary, our work offers additional insights into the evolutionary mechanisms behind tumor progression, provides a different PET/CT-based biomarker, and reveals that an activity hotspot closer to the tumor periphery is associated to a worst patient outcome.

Intensity threshold based solid tumour segmentation method for Positron Emission Tomography (PET) images: A review

Accurate, robust and reproducible delineation of tumour in Positron Emission Tomography (PET) is essential for diagnosis, treatment planning and response assessment. Since standardized uptake value (SUV) – a normalized semiquantitative parameter used in PET is represented by the intensity of the PET images and related to the radiotracer uptake, a SUV based threshold method is a natural choice to delineate the tumour. However, determination of an optimum threshold value is a challenging task due to low spatial resolution, and signal-to-noise ratio (SNR) along with finite image sampling constraint. The aim of the review is to summarize different fixed and adaptive threshold-based PET image segmentation approaches under a common mathematical framework Advantages and disadvantages of different threshold based methods are also highlighted from the perspectives of diagnosis, treatment planning and response assessment. Several fixed threshold values (30%–70% of the maximum SUV of the tumour (SUV_maxT)) have been investigated. It has been reported that the fixed threshold-based method is very much dependent on the SNR, tumour to background ratio (TBR) and the size of the tumour. Adaptive threshold-based method, an alternative to fixed threshold, can minimize these dependencies by accounting for tumour to background ratio (TBR) and tumour size. However, the parameters for the adaptive methods need to be calibrated for each PET camera system (e.g., scanner geometry, image acquisition protocol, reconstruction algorithm etc.) and it is not straight forward to implement the same procedure to other PET systems to obtain similar results. It has been reported that the performance of the adaptive methods is also not optimum for smaller volumes with lower TBR and SNR. Statistical analysis carried out on the NEMA thorax phantom images also indicates that regions segmented by the fixed threshold method are significantly different for all cases. On the other hand, the adaptive method provides significantly different segmented regions only for low TBR with different SNR. From this viewpoint, a robust threshold based segmentation method that will be less sensitive to SUVmaxT, SNR, TBR and volume needs to be developed. It was really challenging to compare the performance of different threshold-based methods because the performance of each method was tested on dissimilar data set with different data acquisition and reconstruction protocols along with different TBR, SNR and volumes. To avoid such difficulties, it will be desirable to have a common database of clinical PET images acquired with different image acquisition protocols and different PET cameras to compare the performance of automatic segmentation methods. It is also suggested to report the changes in SNR and TBR while reporting the response using threshold based methods.

COV is a readily available quantitative indicator of metabolic heterogeneity for predicting survival of patients with early and locally advanced NSCLC manifesting as central lung cancer

OBJECTIVES

The aim of our study was to investigate the value of a simple metabolic heterogeneity parameter, COV (coefficient of variation), by 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the prognosis prediction of central lung cancer in early and locally advanced non-small-cell lung cancer (NSCLC).

METHODS

Seventy-three patients with NSCLC manifesting as central lung cancer were included retrospectively, and we used the COV to evaluate metabolic heterogeneity. Univariate and multivariate analyses were used to evaluate the predictive value in terms of overall survival (OS) and progression-free survival (PFS).

RESULT

For all 73 patients with pathologically confirmed NSCLC, 69.9 % had SCC, and 30.1 % had ADC or other types of NSCLC. The COV was a statistically significant factor in the univariate analysis for the OS rate. The optimal cut-off value was 23.1366, with sensitivity = 0.737 and specificity = 0.771. The COV values were dichotomized by this value and included with atelectasis in the Cox multivariate analysis. Both COV and atelectasis were independent risk factors for OS as follows: for COV (HR, 3.162, P = 0.0002), the 2-year OS rate was 62.5 % and 26.9 % in the low and high COV groups, respectively. For atelectasis (HR 2.047, P = 0.041), the 2-year OS rate was 30.6 % and 65.2 % in the groups with and without atelectasis, respectively (P = 0.017). For PFS, only COV (HR, 2.636, P = 0.001) was a significant predictor. The 2-year PFS rate was 29.7 % in the low COV group and 8% in the high COV group.

CONCLUSION

The pre-treatment metabolic heterogeneity parameter COV is a simple and easy way to predict the OS and PFS of patients with NSCLC manifesting as central lung cancer. Therefore, COV plays an important role in prognostic risk classification in NSCLC. The presence of atelectasis could also be a risk factor for poor prognosis of OS.

PET and MRI guided adaptive radiotherapy: Rational, feasibility and benefit

Adaptive radiotherapy (ART) corresponds to various replanning strategies aiming to correct for anatomical variations occurring during the course of radiotherapy. The goal of the article was to report the rational, feasibility and benefit of using PET and/or MRI to guide this ART strategy in various tumor localizations. The anatomical modifications defined by scanner taking into account tumour mobility and volume variation are not always sufficient to optimise treatment. The contribution of functional imaging by PET or the precision of soft tissue by MRI makes it possible to consider optimized ART. Today, the most important data for both PET and MRI are for lung, head and neck, cervical and prostate cancers. PET and MRI guided ART appears feasible and safe, however in a very limited clinical experience. Phase I/II studies should be therefore performed, before proposing cost-effectiveness comparisons in randomized trials and before using the approach in routine practice.

Correlation Between FDG Hotspots on Pre-radiotherapy PET/CT and Areas of HNSCC Local Relapse: Impact of Treatment Position and Images Registration Method

Aim: Several series have already demonstrated that intratumoral subvolumes with high tracer avidity (hotspots) in 18F-flurodesoxyglucose positron-emission tomography (FDG-PET/CT) are preferential sites of local recurrence (LR) in various solid cancers after radiotherapy (RT), becoming potential targets for dose escalation. However, studies conducted on head and neck squamous cell carcinoma (HNSCC) found only a moderate overlap between pre- and post-treatment subvolumes. A limitation of these studies was that scans were not performed in RT treatment position (TP) and were coregistred using a rigid registration (RR) method. We sought to study (i) the influence of FDG-PET/CT acquisition in TP and (ii) the impact of using an elastic registration (ER) method to improve the localization of hotpots in HNSCC.

Methods: Consecutive patients with HNSCC treated by RT between March 2015 and September 2017 who underwent FDG-PET/CT in TP at initial staging (PET_A) and during follow-up (PET_R) were prospectively included. We utilized a control group scanned in non treatment position (NTP) from our previous retrospective study. Scans were registered with both RR and ER methods. Various sub-volumes (A_X; x = 30, 40, 50, 60, 70, 80, and 90%SUVmax) within the initial tumor and in the subsequent LR (R_X; x = 40 and 70%SUVmax) were overlaid on the initial PET/CT for comparison [Dice, Jaccard, overlap fraction = OF, common volume/baseline volume = A_XnR_X/A_X, common volume/recurrent volume = A_XnR_X/R_X].

Results: Of 199 patients included, 43 (21.6%) had LR (TP = 15; NTP = 28). The overlap between A₃₀, A₄₀, and A₅₀ sub-volumes on PET_A and the whole metabolic volume of recurrence R₄₀ and R₇₀ on PET_R showed moderate to good agreements (0.41–0.64) with OF and A_XnR_X/R_X index, regardless of registration method or patient position. Comparison of registration method demonstrated OF and A_XnR_X/R_X indices (x = 30% to 50%SUVmax) were significantly higher with ER vs. RR in NTP (p < 0.03), but not in TP. For patient position, the OF and A_XnR_X/R_X indices were higher in TP than in NTP when RR was used with a trend toward significance, particularly for x=40%SUVmax (0.50±0.22 vs. 0.31 ± 0.13, p = 0.094).

Conclusion: Our study suggested that PET/CT acquired in TP improves results in the localization of FDG hotspots in HNSCC. If TP is not possible, using an ER method is significantly more accurate than RR for overlap estimation.

Predicting per-lesion local recurrence in locally advanced non-small cell lung cancer following definitive radiation therapy using pre- and mid-treatment metabolic tumor volume

BACKGROUND

We evaluated whether pre- and mid-treatment metabolic tumor volume (MTV) predicts per lesion local recurrence (LR) in patients treated with definitive radiation therapy (RT, dose≥60 Gy) for locally advanced non-small cell lung cancer (NSCLC).

METHODS

We retrospectively reviewed records of patients with stage III NSCLC treated from 2006 to 2018 with pre- and mid-RT PET-CT. We measured the MTV of treated lesions on the pre-RT (MTVpre) and mid-RT (MTVmid) PET-CT. LR was defined per lesion as recurrence within the planning target volume. Receiver operating characteristic (ROC) curves, cumulative incidence rates, and uni- and multivariable (MVA) competing risk regressions were used to evaluate the association between MTV and LR.

RESULTS

We identified 111 patients with 387 lesions (112 lung tumors and 275 lymph nodes). Median age was 68 years, 69.4% were male, 46.8% had adenocarcinoma, 39.6% had squamous cell carcinoma, and 95.5% received concurrent chemotherapy. Median follow-up was 38.7 months. 3-year overall survival was 42.3%. 3-year cumulative incidence of LR was 26.8% per patient and 11.9% per lesion. Both MTVpre and MTVmid were predictive of LR by ROC (AUC = 0.71 and 0.76, respectively) and were significantly associated with LR on MVA (P = 0.004 and P = 7.1e-5, respectively). Among lesions at lower risk of LR based on MTVpre, higher MTVmid was associated with LR (P = 0.001).

CONCLUSION

Per-lesion, larger MTVpre and MTVmid predicted for increased risk of LR. MTVmid was more highly predictive of LR than MTVpre and if validated may allow for further discrimination of high-risk lesions at mid-RT informing dose painting strategies.

Use of Baseline 18 F-FDG PET/CT to Identify Initial Sub-Volumes Associated With Local Failure After Concomitant Chemoradiotherapy in Locally Advanced Cervical Cancer

Introduction: Locally advanced cervical cancer (CC) patients treated by chemoradiotherapy (CRT) have a significant local recurrence rate. The objective of this work was to assess the overlap between the initial high-uptake sub-volume (V1) on baseline 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scans and the metabolic relapse (V2) sites after CRT in locally advanced CC. Methods: PET/CT performed before treatment and at relapse in 21 patients diagnosed with LACC and treated with CRT were retrospectively analyzed. CT images at the time of recurrence were registered to baseline CT using the 3D Slicer TM Expert Automated Registration module. The corresponding PET images were then registered using the corresponding transform. The fuzzy locally adaptive Bayesian (FLAB) algorithm was implemented using 3 classes (one for the background and the other two for tumor) in PET1 to simultaneously define an overall tumor volume and the sub-volume V1. In PET2, FLAB was implemented using 2 classes (one for background, one for tumor), in order to define V2. Four indices were used to determine the overlap between V1 and V2 (Dice coefficients, overlap fraction, X = (V1nV2)/V1 and Y = (V1nV2)/V2). Results: The mean (±standard deviation) follow-up was 26 ± 11 months. The measured overlaps between V1 and V2 were moderate to good according to the four metrics, with 0.62-0.81 (0.72 ± 0.05), 0.72-1.00 (0.85 ± 0.10), 0.55-1.00 (0.73 ± 0.16) and 0.50-1.00 (0.76 ± 0.12) for Dice, overlap fraction, X and Y, respectively. Conclusion: In our study, the overlaps between the initial high-uptake sub-volume and the recurrent metabolic volume showed moderate to good concordance. These results now need to be confirmed in a larger cohort using a more standardized patient repositioning procedure for sequential PET/CT imaging, as there is potential for RT dose escalation exploiting the pre-treatment PET high-uptake sub-volume.

Impact of positron emission tomography with computed tomography for image-guided radiotherapy

Therapeutic effectiveness in radiotherapy is partly related to correct staging of the disease and then precise therapeutic targeting. Positron emission tomography (PET) allows the stage of many cancers to be determined and therefore is essential before deciding on radiation treatment. The definition of the therapeutic target is essential to obtain correct tumour control and limit side effects. The part of adaptive radiotherapy remains to be defined, but PET by its functional nature makes it possible to define the prognosis of many cancers and to consider radiotherapy adapted to the initial response allowing an increase over the entire metabolic volume, or targeted at a subvolume at risk per dose painting, or with a decrease in the dose in case of good response at interim assessment.

How to work together between nuclear medicine and radiotherapy departments?

Among the available imaging techniques, functional imaging provided by nuclear medicine departments represents a tool of choice for the oncoradiotherapist for targeting tumour activity, with positron emission tomography as the main modality. Before, during or after radiotherapy, functional imaging helps guide the oncoradiotherapist in making decisions and in the strategic choice of pathology management. Setting up a working group to ensure perfect coordination at all levels is the first step. Key points for a common and coordinated management between the two departments are the definition of an organizational logistic, training of personnel at every levels, standardization of nomenclatures, the choice of adapted and common equipment, implementation of regulatory controls, and research/clinical routine continuum. The availability of functional examinations dedicated to radiotherapy in clinical routine is possible and requires a convergence of teams and a pooling of tools and techniques.

Revisiting the identification of tumor sub-volumes predictive of residual uptake after (chemo)radiotherapy: influence of segmentation methods on 18F-FDG PET/CT images

Our aim was to evaluate the impact of the accuracy of image segmentation techniques on establishing an overlap between pre-treatment and post-treatment functional tumour volumes in 18FDG-PET/CT imaging. Simulated images and a clinical cohort were considered. Three different configurations (large, small or non-existent overlap) of a single simulated example was used to elucidate the behaviour of each approach. Fifty-four oesophageal and head and neck (H&N) cancer patients treated with radiochemotherapy with both pre- and post-treatment PET/CT scans were retrospectively analysed. Images were registered and volumes were determined using combinations of thresholds and the fuzzy locally adaptive Bayesian (FLAB) algorithm. Four overlap metrics were calculated. The simulations showed that thresholds lead to biased overlap estimation and that accurate metrics are obtained despite spatially inaccurate volumes. In the clinical dataset, only 17 patients exhibited residual uptake smaller than the pre-treatment volume. Overlaps obtained with FLAB were consistently moderate for esophageal and low for H&N cases across all metrics. Overlaps obtained using threshold combinations varied greatly depending on thresholds and metrics. In both cases overlaps were variable across patients. Our findings do not support optimisation of radiotherapy planning based on pre-treatment 18FDG-PET/CT image definition of high-uptake sub-volumes. Combinations of thresholds may have led to overestimation of overlaps in previous studies.

Prognostic value of post-induction chemotherapy 18F-FDG PET-CT in stage II/III non-small cell lung cancer before (chemo-) radiation

INTRODUCTION

The purpose of our present study was to assess the prognostic impact of FDG PET-CT after induction chemotherapy for patients with inoperable non-small-cell lung cancer (NSCLC).

MATERIAL AND METHODS

This retrospective study included 50 patients with inoperable stage II/III NSCLC from January 2012 to July 2015. They were treated for curative intent with induction chemotherapy, followed by concomitant chemoradiation therapy or sequential radiation therapy. FDG PET-CT scans were acquired at initial staging (PET1) and after the last cycle of induction therapy (PET2). Five parameters were evaluated on both scans: SUVmax, SUVpeak, SUVmean, TLG, MTV, and their respective deltas. The prognostic value of each parameter for overall survival (OS) and progression-free survival (PFS) was evaluated with Cox proportional-hazards regression models.

RESULTS

Median follow-up was 19 months. PET1 parameters, clinical and histopathological data were not predictive of the outcome. TLG2 and ΔTLG were prognostic factors for OS. TLG2 was the only prognostic factor for PFS. For OS, log-rank test showed that there was a better prognosis for patients with TLG2< 69g (HR = 7.1, 95%CI 2.8-18, p = 0.002) and for patients with ΔTLG< -81% after induction therapy (HR = 3.8, 95%CI 1.5-9.6, p = 0.02). After 2 years, the survival rate was 89% for the patients with low TLG2 vs 52% for the others. We also evaluated a composite parameter considering both MTV2 and ΔSUVmax. Patients with MTV2> 23cc and ΔSUVmax> -55% had significantly shorter OS than the other patients (HR = 5.7, 95%CI 2.1-15.4, p< 0.01).

CONCLUSION

Post-induction FDG PET might be an added value to assess the patients' prognosis in inoperable stage II/III NSCLC. TLG, ΔTLG as well as the association of MTV and ΔSUVmax seemed to be valuable parameters, more accurate than clinical, pathological or pretherapeutic imaging data.

PET/CT in radiation oncology

The progressive integration of positron emission tomography/computed tomography (PET/CT) imaging in radiation therapy has its rationale in the biological intertumoral and intratumoral heterogeneity of malignant lesions that require the individual adjustment of radiation dose to obtain an effective local tumor control in cancer patients. PET/CT provides information on the biological features of tumor lesions such as metabolism, hypoxia, and proliferation that can identify radioresistant regions and be exploited to optimize treatment plans. Here, we provide an overview of the basic principles of PET-based target volume selection and definition using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and then we focus on the emerging strategies of dose painting and adaptive radiotherapy using different tracers. Previous studies provided consistent evidence that integration of ¹⁸F-FDG PET/CT in radiotherapy planning improves delineation of target volumes and reduces the uncertainties and variabilities of anatomical delineation of tumor sites. PET-based dose painting and adaptive radiotherapy are feasible strategies although their clinical implementation is highly demanding and requires strong technical, computational, and logistic efforts. Further prospective clinical trials evaluating local tumor control, survival, and toxicity of these emerging strategies will promote the full integration of PET/CT in radiation oncology.

Multidisciplinary consensus statement on the clinical management of patients with stage III non-small cell lung cancer

Stage III non-small cell lung cancer (NSCLC) is a very heterogeneous disease that encompasses patients with resected, potentially resectable and unresectable tumours. To improve the prognostic capacity of the TNM classification, it has been agreed to divide stage III into sub-stages IIIA, IIIB and IIIC that have very different 5-year survival rates (36, 26 and 13%, respectively). Currently, it is considered that both staging and optimal treatment of stage III NSCLC requires the joint work of a multidisciplinary team of expert physicians within the tumour committee. To improve the care of patients with stage III NSCLC, different scientific societies involved in the diagnosis and treatment of this disease have agreed to issue a series of recommendations that can contribute to homogenise the management of this disease, and ultimately to improve patient care.

Radiomics: Principles and radiotherapy applications

Radiomics is defined as the extraction of a large quantity of quantitative image features. The different radiomic indexes that have been proposed in the literature are described as well as the various factors that have an impact on the robustness of these indexes. We will see that several hundred quantitative features can be extracted per lesion and imaging modality. The ever-growing number of features studied raises the question of the statistical method of analysis used. This review addresses the research supporting the clinical use of radiomics in oncology in the staging of disease, discrimination between healthy and pathological tissues, the identification of genetic features, the prediction of patient survival, the response to treatment, the recurrence after radiotherapy and chemoradiotherapy and the side effects. Based on the existing literature, it remains difficult to identify features that should be used for current clinical practice.

Is There a Role for an 18F-fluorodeoxyglucose-derived Biological Boost in Squamous Cell Anal Cancer?

AIMS

To investigate the potential role for a biological boost in anal cancer by assessing whether subvolumes of high 18F-fluorodeoxyglucose (FDG) avidity, identified at outset, are spatially consistent during a course of chemoradiotherapy (CRT).

MATERIALS AND METHODS

FDG-positron emission tomography (FDG-PET) scans from 21 patients enrolled into the ART study (NCT02145416) were retrospectively analysed. In total, 29 volumes including both primary tumours and involved nodes >2 cm were identified. FDG-PET scans were carried out before treatment and on day 8 or 9 of CRT. FDG subvolumes were created using a percentage of maximum FDG avidity at thresholds of 34%, 40%, 50%, on the pre-treatment scans, and 70% and 80% on the subsequent scans. Both FDG-PET scans were deformably registered to the planning computed tomography scan. The overlap fraction and the vector distance were calculated to assess spatial consistency. FDG subvolumes for further investigation had an overlap fraction >0.7, as this has been defined in previous publications as a 'good' correlation.

RESULTS

The median overlap fractions between the diagnostic FDG-PET subvolumes 34%, 40% and 50% of maximum standardised uptake value (SUVmax) and subsequent FDG-PET subvolumes of 70% of SUVmax were 0.97, 0.92 and 0.81. The median overlap fraction between the diagnostic FDG-PET subvolumes 34%, 40% and 50% and subsequent FDG-PET subvolumes of 80% were 1.00, 1.00 and 0.92. The median (range) vector distance values between diagnostic FDG-PET subvolumes 34%, 40% and 50% and subsequent FDG-PET subvolumes of 80% were 0.74 mm (0.19-2.94) 0.74 mm (0.19-3.39) and 0.71 mm (0.2-3.29), respectively. Twenty of 29 volumes (69.0%) achieved a threshold > 0.7 between the FDG 50% subvolume on the diagnostic scan and the FDG 80% subvolume on the subsequent scan.

CONCLUSION

FDG-avid subvolumes identified at baseline were spatially consistent during a course of CRT treatment. The subvolume of 50% of SUVmax on the pre-treatment scan could be considered as a potential target for dose escalation.

Metabolic tumour volume is prognostic in patients with non-small-cell lung cancer treated with stereotactic ablative radiotherapy

Introduction

Stereotactic ablative radiotherapy (sabr) is a relatively new technique for the curative-intent treatment of patients with inoperable early-stage non-small-cell lung cancer (nsclc). Previous studies have demonstrated a prognostic value for positron emission tomography-computed tomography (pet/ct) parameters, including maximal standardized uptake value (suv_max), metabolic tumour volume (mtv), and total lesion glycolysis (tlg) in lung cancer patients. We aimed to determine which pet/ct parameter is most prognostic of local control (lc) and overall survival (os) in patients treated with sabr for nsclc.

Methods

We conducted a retrospective review of patients treated with sabr for stage I inoperable nsclc at BC Cancer between 2009 and 2013. The Akaike information criterion was used to compare the prognostic value of the various pet/ct parameters.

Results

The study included 134 patients with a median age of 76 years. Median tumour diameter was 2.2 cm, gross tumour volume was 8.1 mL, suv_max was 7.9, mtv was 2.4 mL, and tlg was 10.9 suv·mL. The 2-year lc was 92%, and os was 66%. On univariate and multivariate analysis, imaging variables including tumour size, gross tumour volume, suv_max, mtv, and tlg were all associated with worse lc. Tumour size was not associated with significantly worse os, but other imaging variables were. The pet/ct parameter most prognostic of lc was mtv. Compared with suv_max, tlg and mtv were more prognostic of os.

Conclusions

In patients with early-stage nsclc treated with sabr, mtv appears to be prognostic of lc and os.

Delineation of lung cancer with FDG PET/CT during radiation therapy

OBJECTIVES

To propose an easily applicable segmentation method (perPET-RT) for delineation of tumour volume during radiotherapy on interim fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with non-small cell lung cancer (NSCLC).

MATERIAL AND METHODS

Sixty-seven patients (51 primary tumours, 60 lymph nodes), from 4 prospective studies, underwent an FDG PET/CT scan during the fifth week of radiation therapy, using different generations of PET/CT. Per-therapeutic PET/CT scans were delineated in consensus by two experienced physicians leading to the gold standard threshold to be applied. The mathematical expression of Th_opt, the optimal threshold to be applied as a function of the maximum standard uptake value (SUV_max), was determined. The performance of this method (perPET-RT) was assessed by computing the DICE similarity coefficient (DSC) and was compared with 8 fixed threshold values and 3 adaptive thresholding methods.

RESULTS

Th_opt verified the following expression: Th_opt = A.ln(1/SUV_max) + B where A and B were 2 constants. A and B were independent from the generation of PET/CT, but depended on the type of lesions (primary lung tumours vs. lymph nodes). PerPET-RT showed good to very good agreement in comparison to the gold standard. The mean and standard deviation of DSC value was 0.81 ± 0.13 for lung lesions and 0.78 ± 0.15 for lymph nodes. PerPET-RT showed a significant better agreement than the other segmentation methods (p < 0.001), except for one of the adaptive thresholding method ADT (p = 0.11).

CONCLUSION

On the database used, perPET-RT has proven its reliability and accuracy for tumour delineation on per-therapeutic FDG PET/CT using only SUV_max measurement. This method may be used to delineate tumour volume for dose-escalation planning.

TRIAL REGISTRATION

NCT01261598 , NCT01261585 , NCT01576796 .

FDG and FMISO PET-guided dose escalation with intensity-modulated radiotherapy in lung cancer

Background

Concomitant chemo-radiotherapy is the reference treatment for non-resectable locally-advanced Non-Small Cell Lung Cancer (NSCLC). Increasing radiotherapy total dose in the whole tumour volume has been shown to be deleterious. Functional imaging with positron emission tomography (PET/CT) offers the potential to identify smaller and biologically meaningful target volumes that could be irradiated with larger doses without compromising Organs At Risk (OAR) tolerance. This study investigated four scenarios, based on ¹⁸FDG and ¹⁸F-miso PET/CT, to delineate the target volumes and derive radiotherapy plans delivering up to 74Gy.

Method

Twenty-one NSCLC patients, selected from a prospective phase II trial, had ¹⁸FDG- and ¹⁸F-miso PET/CT before the start of radiotherapy and ¹⁸FDG PET/CT during the radiotherapy (42Gy). The plans were based planned on a standard plan delivering 66 Gy (plan 1) and on three different boost strategies to deliver 74Gy total dose in pre-treatment ¹⁸FDG hotspot (70% of SUV_max) (plan 2), pre-treatment ¹⁸F-miso target (SUV_max > 1.4) (plan 3) and per-treatment ¹⁸FDG residual (40% of SUV_max). (plan 4).

Results

The mean target volumes were 4.8 cc (± 1.1) for ¹⁸FDG hotspot, 38.9 cc (± 14.5) for ¹⁸F-miso and 36.0 cc (± 10.1) for per-treatment ¹⁸FDG. In standard plan (66 Gy), the mean dose covering 95% of the PTV (D95%) were 66.5 (± 0.33), 66.1 (± 0.32) and 66.1 (± 0.32) Gy for ¹⁸FDG hotspot, ¹⁸F-miso and per-treatment ¹⁸FDG. In scenario 2, the mean D95% was 72.5 (± 0.25) Gy in ¹⁸FDG hotspot versus 67.9 (± 0.49) and 67.9 Gy (± 0.52) in ¹⁸F-miso and per-treatment ¹⁸FDG, respectively. In scenario 3, the mean D95% was 72.2 (± 0.27) Gy to ¹⁸F-miso versus 70.4 (± 0.74) and 69.5Gy (± 0.74) for ¹⁸FDG hotspot and per-treatment ¹⁸FDG, respectively. In scenario 4, the mean D95% was 73.1 (± 0.3) Gy to ¹⁸FDG per-treatment versus 71.9 (± 0.61) and 69.8 (± 0.61) Gy for ¹⁸FDG hotspot and ¹⁸F-miso, respectively. The dose/volume constraints to OARs were matched in all scenarios.

Conclusion

Escalated doses can be selectively planned in NSCLC target volumes delineated on ¹⁸FDG and ¹⁸F-miso PET/CT functional images. The most relevant strategy should be investigated in clinical trials.

Trial registration

(RTEP5, NCT01576796, registered 15 june 2012)

Treatment Outcome Prediction for Cancer Patients based on Radiomics and Belief Function Theory

In this study, we proposed a new radiomics-based treatment outcome prediction model for cancer patients. The prediction model is developed based on belief function theory (BFT) and sparsity learning to address the challenges of redundancy, heterogeneity, and uncertainty of radiomic features, and relatively small-sized and unbalanced training samples. The model first selects the most predictive feature subsets from relatively large amounts of radiomic features extracted from pre- and/or in-treatment positron emission tomography (PET) images and available clinical and demographic features. Then an evidential k-nearest neighbor (EK-NN) classifier is proposed to utilize the selected features for treatment outcome prediction. Twenty-five stage II-III lung, 36 esophagus, 63 stage II-III cervix, and 45 lymphoma cancer patient cases were included in this retrospective study. Performance and robustness of the proposed model were assessed with measures of feature selection stability, outcome prediction accuracy, and receiver operating characteristics (ROC) analysis. Comparison with other methods were conducted to demonstrate the feasibility and superior performance of the proposed model.

Stereotactic radiotherapy boost after definite chemoradiation for non-responding locally advanced NSCLC based on early response monitoring 18F-FDG-PET/CT

Background and purpose

Prognosis of locally advanced non-small cell lung cancer remains poor despite chemoradiation. This planning study evaluated a stereotactic boost after concurrent chemoradiotherapy (30 × 2 Gy) to improve local control. The maximum achievable boost directed to radioresistant primary tumor subvolumes based on pre-treatment fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) (pre-treatment-PET) and on early response monitoring ¹⁸F-FDG-PET/CT (ERM-PET) was compared.

Materials and methods

For ten patients, a stereotactic boost (VMAT) was planned on ERM-PET (PTV_boost;ERM) and on pre-treatment-PET (PTV_{boost;pre-treatment}), using a 70% SUV_max threshold with 7 mm margin to segmentate radioresistant subvolumes. Dose was escalated till organ at risk (OAR) constraints were met, aiming to plan at least 18 Gy in 3 fractions (EQD₂ 84 Gy/BED 100.8 Gy).

Results

In five patients, PTV_boost;ERM was 9-40% smaller relative to PTV_{boost;pre-treatment}. Overlap of PTV_boost;ERM with OARs decreased also compared to overlap of PTV_{boost;pre-treatment} with OARs. However, any overlap with OAR remained in 4/5 patients resulting in minimal differences between planned dose before and during treatment. Median dose (EQD₂) covering 99% and 95% of PTV_boost;ERM were 15 Gy and 18 Gy respectively. Median boost volume receiving a physical dose of  ≥ 18 Gy (V18) was 88%. V18 was ≥ 80% for PTV_boost in six patients.

Conclusions

A significant stereotactic boost to volumes with high initial or persistent ¹⁸F-FDG-uptake could be planned above 60 Gy chemoradiation. Differences between planned dose before and during treatment were minimal. However, as an ERM-PET also monitors changes in tumor position, we recommend to plan the boost on the ERM-PET.

Image-guided adaptive radiotherapy in patients with locally advanced non-small cell lung cancer: the art of PET

With a worldwide annual incidence of 1.8 million cases, lung cancer is the most diagnosed form of cancer in men and the third most diagnosed form of cancer in women. Histologically, 80-85% of all lung cancers can be categorized as non-small cell lung cancer (NSCLC). For patients with locally advanced NSCLC, standard of care is fractionated radiotherapy combined with chemotherapy. With the aim of improving clinical outcome of patients with locally advanced NSCLC, combined and intensified treatment approaches are increasingly being used. However, given the heterogeneity of this patient group with respect to tumor biology and subsequent treatment response, a personalized treatment approach is required to optimize therapeutic effect and minimize treatment induced toxicity. Medical imaging, in particular positron emission tomography (PET), before and during the course radiotherapy is increasingly being used to personalize radiotherapy. In this setting, PET imaging can be used to improve delineation of target volumes, employ molecularly-guided dose painting strategies, early response monitoring, prediction and monitoring of treatment-related toxicity. The concept of PET image-guided adaptive radiotherapy (IGART) is an interesting approach to personalize radiotherapy for patients with locally advanced NSCLC, which might ultimately contribute to improved clinical outcomes and reductions in frequency of treatment-related adverse events in this patient group. In this review, we provide a comprehensive overview of available clinical data supporting the use of PET imaging for IGART in patients with locally advanced NSCLC.

Local failure after radical radiotherapy of non-small cell lung cancer in relation to the planning FDG-PET/CT

OBJECTIVES

Local recurrence (rec) in lung cancer is associated with poor survival. This study examined whether the pattern of failure is associated with the most PET avid volume in the planning-FDG-PET/CT scan (p-PET/CT).

METHODS

162 consecutive inoperable NSCLC patients (pts) receiving radiotherapy between January 2012 and April 2014 were reviewed. Radiotherapy was delivered in 2 Gy/fraction (5f/week) to a total dose of 60-66 Gy. Pts were followed with CT scans every third month. Patients with local rec as first event were analyzed. For the primary tumor (T) the overlap-fraction (OF) between 50% of SUV_peak on p-PET/CT and the volume of T-rec was calculated: OF = (SUV_p50∩T-rec)/min(SUV_p50, T-rec). Similarly for the GTV on the p-CT: OF = (GTV∩T-rec)/min(GTV, T-rec). OF was based on a rigid registration between p-PET/CT and rec-CT with PET guided delineation of T- rec. For lymph nodes (LN), the correlation between the location of treated-LN and the location of recurrence-LN was evaluated.

RESULTS

67 patients developed local rec. 51 pts had rec in T-site, 45 pts in LN-site. Due to anatomical changes, reliable registration between p-CT and rec-CT was only obtained in 26 pts with T-rec. The median OF_SUVp50 was 52, 8% [range 26; 100%] and the median OF_GTV was 80.5% [19.7; 100%]. Eleven pts had higher OF_SUVp50 than OF_GTV. LN-rec predominantly occurred in the station 2R (32%), 4R (46%), 7 (46%) and right hilum (36%). Pts with malignant LNs in station 4R or 7 on p-CT had a high risk of rec in these stations; 4R (55%) and 7 (83%).

CONCLUSIONS

This study indicates that the most PET active volume on p-PET-CT is a driver for rec at T-site. LN-recurrences predominantly appear in station 2R, 4R, 7 and right hilum. Additional confirmatory studies regarding lymph node mapping and selective lymph node irradiation is needed.

Rationale and Protocol for a Canadian Multicenter Phase II Randomized Trial Assessing Selective Metabolically Adaptive Radiation Dose Escalation in Locally Advanced Non-small-cell Lung Cancer (NCT02788461)

We explain the rationale for metabolically adaptive radiation dose escalation in stage III non-small-cell lung cancer and describe the design of a Canadian phase II randomized trial investigating this approach. In the trial, patients are randomized to either conventional chemoradiation treatment (60 Gy in 30 fractions) or metabolically adaptive chemoradiation, where fluorodeoxyglucose-avid tumor sub-volumes receive an integrated boost dose to a maximum of 85 Gy in 30 fractions. The trial sample size is 78 patients, and the target population is patients with newly diagnosed, inoperable stage III non-small-cell lung cancer treated with radical intent chemoradiation. The primary objective of the trial is to determine if dose escalation to metabolically active sub-volumes will reduce 2-year local-regional failure rate from 42.3% to 22.3%, when compared with standard treatment. The secondary objectives are to determine the effect of dose escalation on overall survival, progression-free survival, quality of life, and rate of grade 3 to 5 toxicities.

Use of baseline 18F-FDG PET scan to identify initial sub-volumes with local failure after concomitant radio-chemotherapy in head and neck cancer

Introduction

Head and neck squamous cell carcinoma (HNSCC) treated by radio-chemotherapy have a significant local recurrence rate. It has been previously suggested that 18F-FDG PET could identify the high uptake areas that can be potential targets for dose boosting. The purpose of this study was to compare the location of initial hypermetabolic regions on baseline scans with the metabolic relapse sites after radio-chemotherapy in HNSCC.

Results

The initial functional tumor volume was significantly higher for patients with proven local recurrence or residual disease (23.5 cc vs. 8.9 cc; p = 0.0005). The overlap between baseline and follow-up sub-volumes were moderate with an overlap fraction ranging from 0.52 to 0.39 between R40 and I30 to I60.

Conclusion

In our study the overlap between baseline and post-therapeutic metabolic tumor sub-volumes was only moderate. These results need to be investigated in a larger cohort acquired with a more standardized patient repositioning protocol for sequential PET imaging.

Methods

Pre and post treatment PET/CT scans of ninety four HNSCC patients treated with radio-chemotherapy were retrospectively reviewed. Follow-up 18F-FDG PET/CT images were registered to baseline scans using a rigid body transformation. Seven metabolic tumor sub-volumes were obtained on the baseline scans using a fixed percentage of SUV_max (I30, I40, I50, I60, I70, I80, and I90) and were subsequently compared with two post-treatment sub-volumes (R40, R90) in 38 cases of local recurrence or residual metabolic disease. Overlap fraction, Dice and Jaccard indices, common volume/baseline volume and common volume/recurrent volume were used to determine the overlap of the different estimated sub-volumes.

18F-deoxyglucose positron emission tomography/computed tomography to predict local failure in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) patients are at risk for local failure (LF) following treatment. Predicting tumor regions at high risk for local failure before radiotherapy may increase treatment efficacy by permitting an escalated radiation dose specifically to those regions critical for tumor control. Forty-one patients with non-resectable locally advanced ESCC underwent ¹⁸F-deoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging before concurrent chemoradiotherapy (CCRT). After CCRT, a second (failure) FDG PET/CT was performed in cases of relapse. Failure FDG PET/CT scans were fused to pre-treatment scans to identify tumor regions at high risk for LF. Within a median follow-up time of 26 months, 20 patients (48.8%) had LF. In 19 patients, the failure occurred within a pre-treatment high FDG uptake region; the failure occurred outside these regions in only one patient. Pre-treatment metabolic tumor volume (MTV) was independently associated with LF (P<0.001, HR 1.128, 95% CI: 1.061–1.198). LF was more likely in patients with MTVs ≥27 cm³. In initial PET/CT images, when 50% maximum standardized uptake value (SUV_max) was used as the threshold, delineated subvolumes overlapped LF regions. These results confirm that LF occurs most commonly within pre-treatment high FDG uptake regions.

Target volume delineation of anal cancer based on magnetic resonance imaging or positron emission tomography

Purpose

To compare target volume delineation of anal cancer using positron emission tomography (PET) and magnetic resonance imaging (MRI) with respect to inter-observer and inter-modality variability.

Methods

Nineteen patients with anal cancer undergoing chemoradiotherapy were prospectively included. Planning computed tomography (CT) images were co-registered with 18F–fluorodexocyglucose (FDG) PET/CT images and T2 and diffusion weighted (DW) MR images. Three oncologists delineated the Gross Tumor Volume (GTV) according to national guidelines and the visible tumor tissue (GTV_T). MRI and PET based delineations were evaluated by absolute volumes and Dice similarity coefficients.

Results

The median volume of the GTVs was 27 and 31 cm³ for PET and MRI, respectively, while it was 6 and 11 cm³ for GTV_T. Both GTV and GTV_T volumes were highly correlated between delineators (r = 0.90 and r = 0.96, respectively). The median Dice similarity coefficient was 0.75 when comparing the GTVs based on PET/CT (GTV_PET) with the GTVs based on MRI and CT (GTV_MRI). The median Dice coefficient was 0.56 when comparing the visible tumor volume evaluated by PET (GTV_{T_PET}) with the same volume evaluated by MRI (GTV_{T_MRI}). Margins of 1–2 mm in the axial plane and 7–8 mm in superoinferior direction were required for coverage of the individual observer’s GTVs.

Conclusions

The rather good agreement between PET- and MRI-based GTVs indicates that either modality may be used for standard target delineation of anal cancer. However, larger deviations were found for GTV_T, which may impact future tumor boost strategies.

Correlation analysis of [18F]fluorodeoxyglucose and [18F]fluoroazomycin arabinoside uptake distributions in lung tumours during radiation therapy

BACKGROUND

PET-guided dose painting (DP) aims to target radioresistant tumour regions in order to improve radiotherapy (RT) outcome. Besides the well-known [¹⁸F]fluorodeoxyglucose (FDG), the hypoxia positron emission tomography (PET) tracer [¹⁸F]fluoroazomycin arabinoside (FAZA) could provide further useful information to guide the radiation dose prescription. In this study, we compare the spatial distributions of FDG and FAZA PET uptakes in lung tumours.

MATERIAL AND METHODS

Fourteen patients with unresectable lung cancer underwent FDG and FAZA 4D-PET/CT on consecutive days at three time-points: prior to RT (pre), and during the second (w2), and the third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP). The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUV_max), and the hypoxic volume (HV: FAZA SUV > 1.4) were delineated within the gross tumour volume (GTV_CT). FDG and FAZA intratumoral PET uptake distributions were subsequently pairwise compared, using both volume-, and voxel-based analyses.

RESULTS

Volume-based analysis showed large overlap between MTV and HV: median overlapping fraction was 0.90, 0.94 and 0.94, at the pre, w2 and w3 time-points, respectively. Voxel-wise analysis between FDG and FAZA intratumoral PET uptake distributions showed high correlation: median Spearman's rank correlation coefficient was 0.76, 0.77 and 0.76, at the pre, w2 and w3 time-points, respectively. Interestingly, tumours with high FAZA uptake tended to show more similarity between FDG and FAZA intratumoral uptake distributions than those with low FAZA uptake.

CONCLUSIONS

In unresectable lung carcinomas, FDG and FAZA PET uptake distributions displayed unexpectedly strong similarity, despite the distinct pathways targeted by these tracers. Hypoxia PET with FAZA brought very little added value over FDG from the perspective of DP in this population.

Local Radiotherapy Intensification for Locally Advanced Non-small-cell Lung Cancer - A Call to Arms

Chemoradiotherapy, the standard of care for locally advanced non-small-cell lung cancer (NSCLC), often fails to eradicate all known disease. Despite advances in chemotherapeutic regimens, locally advanced NSCLC remains a difficult disease to treat, and locoregional failure remains common. Improved radiographic detection can identify patients at significant risk of locoregional failure after definitive treatment, and newer methods of escalating locoregional treatment may allow for improvements in locoregional control with acceptable toxicity. This review addresses critical issues in escalating local therapy, focusing on using serial positron emission tomography-computed tomography to select high-risk patients and employing stereotactic radiotherapy to intensify treatment. We further propose a clinical trial concept that incorporates the review's findings.

Evolution of [18F]fluorodeoxyglucose and [18F]fluoroazomycin arabinoside PET uptake distributions in lung tumours during radiation therapy

BACKGROUND

Dose painting (DP) aims to improve radiation therapy (RT) outcome by targeting radioresistant tumour regions identified through functional imaging, e.g., positron emission tomography (PET). Importantly, the expected benefit of DP relies on the ability of PET imaging to identify tumour areas which could be consistently targeted throughout the treatment. In this study, we analysed the spatial stability of two potential DP targets in lung cancer patients undergoing RT: the tumour burden surrogate [¹⁸F]fluorodeoxyglucose (FDG) and the hypoxia surrogate [¹⁸F]fluoroazomycin arabinoside (FAZA).

MATERIALS AND METHODS

Thirteen patients with unresectable lung tumours underwent FDG and FAZA 4D-PET/CT before (pre), and during the second (w2) and third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP) for further analysis. The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUV_max) and the hypoxic volume (HV: FAZA SUV >1.4) were delineated within the gross tumour volume (GTV_CT). The stability of FDG and FAZA PET uptake distributions during RT was subsequently assessed through volume-overlap analysis and voxel-based correlation analysis.

RESULTS

The volume-overlap analysis yielded median overlapping fraction (OF) of 0.86 between MTV_pre and MTV_w2 and 0.82 between MTV_pre and MTV_w3. In patients with a detectable HV, median OF was 0.82 between HV_pre and HV_w2 and 0.90 between HV_pre and HV_w3. The voxel-based correlation analysis yielded median Spearman's correlation coefficient (r_S) of 0.87 between FDG_pre and FDG_w2 and 0.83 between FDG_pre and FDG_w3. Median r_S was 0.78 between FAZA_pre and FAZA_w2 and 0.79 between FAZA_pre and FAZA_w3.

CONCLUSIONS

FDG and FAZA PET uptake distributions were spatially stable during the 3 first weeks of RT in patients with unresectable lung cancer, both based on volume- and voxel-based indicators. This might allow for a consistent targeting of high FDG or FAZA PET uptake regions as part of a DP strategy.

[Analysis of the Role of PET/CT SUVmax in Prognosis and Its Correlation with Clinicopathological Characteristics in Resectable Lung Squamous Cell Carcinoma]

背景与目的

肺癌居于全球男性及女性癌症相关死亡原因的首位，大多数患者在确诊时已属晚期，5年生存率仅为18%。肺癌可分为非小细胞肺癌（non-small cell lung carcinoma, NSCLC）和小细胞癌（small cell lung carcinoma, SCLC），其中NSCLC占肺癌的80%-85%，NSCLC根据组织学可主要分为腺癌（约占40%），鳞状细胞癌（20%-30%）和大细胞癌（10%），针对驱动基因的靶向治疗在肺腺癌中取得一定成绩，但在肺鳞癌的治疗中收效甚微，肺鳞癌的诊治更需得到关注，¹⁸F-脱氧葡萄糖（fluorodeoxyglucose, FDG）正电子发射断层扫描/计算机体层摄影（positron emission tomography/computed tomography, PET/CT）越来越多地应用于肺癌的诊断与分期中，本研究旨在探讨¹⁸F-FDG PET/CT原发灶最大标准摄取值（maximum standardized uptake value, SUVmax）在肺鳞癌患者术后预后中的意义及与临床病理特征的关系。

方法

回顾分析2005年5月-2014年10月收治的182例初治、接受PET/CT检查、行根治术的原发肺鳞癌患者的临床影像病理及随访资料。采用Kaplan-Meier法及Cox模型分析患者生存情况，并分析原发灶SUVmax与各临床病理因素的关系。

结果

182例肺鳞癌患者原发灶SUVmax以13.0为界分为两组，SUVmax > 13.0组与≤13.0组患者的中位总生存期分别为56个月和87个月，差异具有统计学意义（P=0.022）。原发灶SUVmax与性别、肿瘤最大径、肿瘤-淋巴结-转移（tumor-node-metastasis, TNM）分期、中性粒细胞、中性粒细胞/淋巴细胞比例（neutrophil-lymphocyte ratio, NLR）存在正相关性，与血红蛋白呈负相关（P < 0.05）。Cox多因素分析显示SUVmax（HR=1.714, 95%CI: 1.021-2.876, P=0.042）、TNM分期（HR=1.677, 95%CI: 1.231-2.284, P=0.001）均为患者生存的独立预后影响因子，提示SUVmax有独立于病理TNM分期之外的预后价值。而且，SUVmax在Ⅰ期肺鳞癌患者的预后中有意义（P=0.045）。

结论

PET/CT SUVmax对肺鳞癌患者术后生存的预测有重要的价值，是独立于TNM分期之外的一个重要预后因素，并且原发灶SUVmax与多个临床病理因素间存在相关性。

Correlation between fluorodeoxyglucose hotspots on pretreatment positron emission tomography/CT and preferential sites of local relapse after chemoradiotherapy for head and neck squamous cell carcinoma

BACKGROUND

The potential benefits of ¹⁸ F-fluoro-2-deoxy-D-glucose-positron emission tomography/CT (FDG-PET/CT) imaging for radiotherapy (RT) treatment planning of head and neck squamous cell carcinoma (HNSCC) are increasingly being recognized. It has been suggested that intratumoral subvolumes with high FDG avidity ("hotspots") are potential targets for selected dose escalation. The purposes of this study were to demonstrate that pre-RT FDG-PET/CT can identify intratumoral sites at increased risk of local relapse after RT and to determine an optimal threshold to delineate smaller RT target volumes that would facilitate RT dose escalation without impaired tolerance.

METHODS

Seventy-two consecutive patients with locally advanced HNSCC treated by RT ± chemotherapy were included in this study. All patients underwent FDG-PET/CT at initial staging (PET_A ) and during systematic follow-up (PET_R ). FDG-PET/CT was coregistered on the initial CT scan with a rigid method. Various subvolumes (A_X ; × = 30%, 40%, 50%, 60%, 70%, 80%, and 90% standardized uptake value maximum [SUVmax] thresholds) within the primary tumor and in the subsequent local relapse (R_X ; × = 40% and 70% SUVmax thresholds) were compared together (Dice, Jaccard, overlap fraction, common volume/baseline volume, and common volume/recurrent volume).

RESULTS

Nineteen patients (26%) had local relapses. Using a 40% SUVmax threshold, the initial metabolic tumor volume was significantly higher in patients with local relapses than in controlled patients (10.4 ± 8.6 vs 5.1 ± 4.9 cc; p = .002) as well as total lesion glycolysis (117.9 ± 88.6 vs 60.6 ± 80.4; p = .013). For both methods, the overlap index among A₃₀ , A₄₀ , and A₅₀ subvolumes on PET_A and the whole metabolic volume of recurrence R₄₀ and R₇₀ on PET_R showed a moderate agreement (0.52 to 0.43).

CONCLUSION

Our study does not find high overlap index values between the initial tumor and recurrence subvolumes, probably because of a suboptimal coregistration. Our results also confirm that metabolic tumor volume and total lesion glycolysis are independently correlated with recurrence-free survival in patients with HNSCC. Further larger prospective studies with FDG-PET/CT performed in the same RT position and with a validated elastic registration method are needed. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1155-1165, 2017.

Phase II Study of a Radiotherapy Total Dose Increase in Hypoxic Lesions Identified by 18F-Misonidazole PET/CT in Patients with Non-Small Cell Lung Carcinoma (RTEP5 Study)

See an invited perspective on this article on page 1043.This multicenter phase II study investigated a selective radiotherapy dose increase to tumor areas with significant ¹⁸F-misonidazole (¹⁸F-FMISO) uptake in patients with non-small cell lung carcinoma (NSCLC). Methods: Eligible patients had locally advanced NSCLC and no contraindication to concomitant chemoradiotherapy. The ¹⁸F-FMISO uptake on PET/CT was assessed by trained experts. If there was no uptake, 66 Gy were delivered. In ¹⁸F-FMISO-positive patients, the contours of the hypoxic area were transferred to the radiation oncologist. It was necessary for the radiotherapy dose to be as high as possible while fulfilling dose-limiting constraints for the spinal cord and lungs. The primary endpoint was tumor response (complete response plus partial response) at 3 mo. The secondary endpoints were toxicity, disease-free survival (DFS), and overall survival at 1 y. The target sample size was set to demonstrate a response rate of 40% or more (bilateral α = 0.05, power 1-β = 0.95). Results: Seventy-nine patients were preincluded, 54 were included, and 34 were ¹⁸F-FMISO-positive, 24 of whom received escalated doses of up to 86 Gy. The response rate at 3 mo was 31 of 54 (57%; 95% confidence interval [CI], 43%-71%) using RECIST 1.1 (17/34 responders in the ¹⁸F-FMISO-positive group). DFS and overall survival at 1 y were 0.86 (95% CI, 0.77-0.96) and 0.63 (95% CI, 0.49-0.74), respectively. DFS was longer in the ¹⁸F-FMISO-negative patients (P = 0.004). The radiotherapy dose was not associated with DFS when adjusting for the ¹⁸F-FMISO status. One toxic death (66 Gy) and 1 case of grade 4 pneumonitis (>66 Gy) were reported. Conclusion: Our approach results in a response rate of 40% or more, with acceptable toxicity. ¹⁸F-FMISO uptake in NSCLC patients is strongly associated with poor prognosis features that could not be reversed by radiotherapy doses up to 86 Gy.

The Role of PET/CT Molecular Imaging in the Diagnosis of Recurrence and Surveillance of Patients Treated for Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide and its prognosis remains poor. Molecular imaging with ¹⁸F-FDG PET/CT can metabolically characterize the nature of lesions as benign or malignant, allowing a better staging at the diagnosis of this kind of patient. This advantage can also be applied in the re-staging due to the suspicion of recurrent disease. Many patients have a recurrence of the disease, including surgically treated patients. In the current context, with new personalized oncological treatments, the surveillance for recurrence and its accurate diagnosis are crucial to improve their survival. In this paper, we revise the current knowledge about the clinical and molecular factors related to the recurrent disease. In the context of new, promising, available personalized treatments, the role of molecular imaging with PET/CT and ¹⁸F-FDG and non-¹⁸F-FDG radiotracers in the follow-up of NSCLC-treated patients is especially attractive and interesting.

[Role of functional imaging in the definition of target volumes for lung cancer radiotherapy]

Functional imaging with positron emission tomography (PET) is interesting to optimize lung radiotherapy planning, and probably to deliver a heterogeneous dose or adapt the radiation dose during treatment. Only fluorodeoxyglucose (FDG) PET-computed tomography (CT) is validated for staging lung cancer and planning radiotherapy. The optimal segmentation methods remain to be defined as well as the interest of "dose painting" from pre-treatment PET (metabolism: FDG) or hypoxia (fluoromisonidazole: FMISO) and the interest of replanning based on pertherapeutic PET.

Local respiratory motion correction for PET/CT imaging: Application to lung cancer

PURPOSE

Despite multiple methodologies already proposed to correct respiratory motion in the whole PET imaging field of view (FOV), such approaches have not found wide acceptance in clinical routine. An alternative can be the local respiratory motion correction (LRMC) of data corresponding to a given volume of interest (VOI: organ or tumor). Advantages of LRMC include the use of a simple motion model, faster execution times, and organ specific motion correction. The purpose of this study was to evaluate the performance of LMRC using various motion models for oncology (lung lesion) applications.

METHODS

Both simulated (NURBS based 4D cardiac-torso phantom) and clinical studies (six patients) were used in the evaluation of the proposed LRMC approach. PET data were acquired in list-mode and synchronized with respiration. The implemented approach consists first in defining a VOI on the reconstructed motion average image. Gated PET images of the VOI are subsequently reconstructed using only lines of response passing through the selected VOI and are used in combination with a center of gravity or an affine/elastic registration algorithm to derive the transformation maps corresponding to the respiration effects. Those are finally integrated in the reconstruction process to produce a motion free image over the lesion regions.

RESULTS

Although the center of gravity or affine algorithm achieved similar performance for individual lesion motion correction, the elastic model, applied either locally or to the whole FOV, led to an overall superior performance. The spatial tumor location was altered by 89% and 81% for the elastic model applied locally or to the whole FOV, respectively (compared to 44% and 39% for the center of gravity and affine models, respectively). This resulted in similar associated overall tumor volume changes of 84% and 80%, respectively (compared to 75% and 71% for the center of gravity and affine models, respectively). The application of the nonrigid deformation model in LRMC led to over an order of magnitude gain in computational efficiency of the correction relative to the application of the deformable model to the whole FOV.

CONCLUSIONS

The results of this study support the use of LMRC as a flexible and efficient correction approach for respiratory motion effects for single lesions in the thoracic area.

Performance of automatic image segmentation algorithms for calculating total lesion glycolysis for early response monitoring in non-small cell lung cancer patients during concomitant chemoradiotherapy

BACKGROUND AND PURPOSE

This study evaluated the use of total lesion glycolysis (TLG) determined by different automatic segmentation algorithms, for early response monitoring in non-small cell lung cancer (NSCLC) patients during concomitant chemoradiotherapy.

MATERIALS AND METHODS

Twenty-seven patients with locally advanced NSCLC treated with concomitant chemoradiotherapy underwent (18)F-fluorodeoxyglucose (FDG) PET/CT imaging before and in the second week of treatment. Segmentation of the primary tumours and lymph nodes was performed using fixed threshold segmentation at (i) 40% SUVmax (T40), (ii) 50% SUVmax (T50), (iii) relative-threshold-level (RTL), (iv) signal-to-background ratio (SBR), and (v) fuzzy locally adaptive Bayesian (FLAB) segmentation. Association of primary tumour TLG (TLGT), lymph node TLG (TLGLN), summed TLG (TLGS=TLGT+TLGLN), and relative TLG decrease (ΔTLG) with overall-survival (OS) and progression-free survival (PFS) was determined using univariate Cox regression models.

RESULTS

Pretreatment TLGT was predictive for PFS and OS, irrespective of the segmentation method used. Inclusion of TLGLN improved disease and early response assessment, with pretreatment TLGS more strongly associated with PFS and OS than TLGT for all segmentation algorithms. This was also the case for ΔTLGS, which was significantly associated with PFS and OS, with the exception of RTL and T40.

CONCLUSIONS

ΔTLGS was significantly associated with PFS and OS, except for RTL and T40. Inclusion of TLGLN improves early treatment response monitoring during concomitant chemoradiotherapy with FDG-PET.

Fluorodeoxyglucose Uptake on Positron Emission Tomography Is a Useful Predictor of Long-Term Pain Control After Palliative Radiation Therapy in Patients With Painful Bone Metastases: Results of a Single-Institute Prospective Study

PURPOSE

To determine whether fluorodeoxyglucose positron emission tomography (FDG-PET) before and after palliative radiation therapy (RT) can predict long-term pain control in patients with painful bone metastases.

METHODS AND MATERIALS

Thirty-one patients with bone metastases who received RT were prospectively included. Forty painful metastatic treatment fields were evaluated. All patients had undergone pre-RT and post-RT PET/CT scanning. We evaluated the relationships between the pre-RT, post-RT, and changes in maximum standardized uptake value (SUVmax) and the pain response, and between SUVmax and pain relapse of the bone metastases in the treatment field. In addition, we compared the SUVmax according to the length of time from the completion of RT to pain relapse of the bone metastases.

RESULTS

Regarding the pain response at 4 weeks after the completion of RT, there were 36 lesions of 27 patients in the responder group and 4 lesions of 4 patients in the nonresponder group. Changes in the SUVmax differed significantly between the responder and nonresponder groups in both the early and delayed phases (P=.0292 and P=.0139, respectively), but no relationship was observed between the pre-RT and post-RT SUVmax relative to the pain response. The responder group was evaluated for the rate of relapse. Thirty-five lesions of 26 patients in the responder group were evaluated, because 1 patient died of acute renal failure at 2 months after RT. Twelve lesions (34%) showed pain relapse, and 23 lesions (66%) did not. There were significant differences between the relapse and nonrelapse patients in terms of the pre-RT (early/delayed phases: P<.0001/P<.0001), post-RT (P=.0199/P=.0261), and changes in SUVmax (P=.0004/P=.004).

CONCLUSIONS

FDG-PET may help predict the outcome of pain control in the treatment field after palliative RT for painful bone metastases.