Role of FDG-PET in the diagnosis and management of lung cancer

Positron emission tomography (PET) using [(18)F]-2-deoxy-2-fluoro-d-glucose (FDG) has emerged as a valuable diagnostic modality in patients with non-small cell lung cancer (NSCLC). Data in the literature show that the addition of FDG-PET definitely alters clinical management in patients with potentially resectable NSCLC by adequately staging the mediastinum and detecting previously unknown distant metastases. Thus, the number of noncurative thoracotomies and unnecessary mediastinoscopies is reduced. Furthermore, there is increasing evidence that FDG-PET will change radiation treatment planning by defining a biologic treatment volume, incorporating unsuspected additional locoregional disease, and avoiding overtreatment by identifying computerized tomography abnormalities as benign. For follow-up during systemic therapy, early FDG-PET appears to be predictive for the response to therapy. However, before FDG-PET-induced changes in patient management can be incorporated into clinical practice both for radiation treatment planning and chemotherapy, technical issues must be resolved, validation studies should be performed and, most importantly, randomized trials are necessary to evaluate the effect of FDG-PET on patient outcome parameters.     

Response to radiation

Computed tomography (CT) has traditionally been the standard radiographic modality for diagnosing and monitoring non-small cell; lung cancer (NSCLC) after treatment. Given the limitations of CT, the utility of 18F-fluoro-2-deoxy-glucose positron emission tomography (FDG-PET) has been investigated for the management of NSCLC, with promising findings. Its adjunctive role with CT in diagnosing and staging disease is well established. FDG-PET also has been found to be a valuable tool for radiation treatment planning because it improves the precision of lesion definition. More recently, its value for determining clinical response both during and after treatment has been explored. This review highlights the various applications of FDG-PET in the diagnosis and management of NSCLC as corroborated by clinical data, with considerations of future directions.     

Impact of FDG-PET on radiation therapy volume delineation in non-small-cell lung cancer

PURPOSE: Locoregional failure remains a significant problem for patients receiving definitive radiation therapy alone or combined with chemotherapy for non-small-cell lung cancer (NSCLC). Positron emission tomography (PET) with [(18)F]fluoro-2-deoxy-d-glucose (FDG) has proven to be a valuable diagnostic and staging tool for NSCLC. This prospective study was performed to determine the impact of treatment simulation with FDG-PET and CT on radiation therapy target volume definition and toxicity profiles by comparison to simulation with computed tomography (CT) scanning alone. METHODS: Twenty-six patients with Stages I-III NSCLC were studied. Each patient underwent sequential CT and FDG-PET simulation on the same day. Immobilization devices used for both simulations included an alpha cradle, a flat tabletop, 6 external fiducial markers, and a laser positioning system. A radiation therapist participated in both simulations to reproduce the treatment setup. Both the CT and fused PET/CT image data sets were transferred to the radiation treatment planning workstation for contouring. Each FDG-PET study was reviewed with the interpreting nuclear radiologist before tumor volumes were contoured. The fused PET/CT images were used to develop the three-dimensional conformal radiation therapy (3DCRT) plan. A second physician, blinded to the results of PET, contoured the gross tumor volumes (GTV) and planning target volumes (PTV) from the CT data sets, and these volumes were used to generate mock 3DCRT plans. The PTV was defined by a 10-mm margin around the GTV. The two 3DCRT plans for each patient were compared with respect to the GTV, PTV, mean lung dose, volume of normal lung receiving > or =20 Gy (V20), and mean esophageal dose. RESULTS: The FDG-PET findings altered the AJCC TNM stage in 8 of 26 (31%) patients; 2 patients were diagnosed with metastatic disease based on FDG-PET and received palliative radiation therapy. Of the 24 patients who were planned with 3DCRT, PET clearly altered the radiation therapy volume in 14 (58%), as follows. PET helped to distinguish tumor from atelectasis in all 3 patients with atelectasis. Unsuspected nodal disease was detected by PET in 10 patients, and 1 patient had a separate tumor focus detected within the same lobe of the lung. Increases in the target volumes led to increases in the mean lung dose, V20, and mean esophageal dose. Decreases in the target volumes in the patients with atelectasis led to decreases in these normal-tissue toxicity parameters. CONCLUSIONS: Radiation targeting with fused FDG-PET and CT images resulted in alterations in radiation therapy planning in over 50% of patients by comparison with CT targeting. The increasing availability of integrated PET/CT units will facilitate the use of this technology for radiation treatment planning. A confirmatory multicenter, cooperative group trial is planned within the Radiation Therapy Oncology Group.     

Intérêt de la tomographie par émission de positons au [18F]-fluoro-2-désoxyglucose dans la détermination des volumes cibles de radiothérapie. Application à l''irradiation conformationnelle des cancers bronchiques non à petites cellules

Traditional radiation treatment planning relies on density imaging such as Computed Tomography for anatomic information of various structures of interest including target and normal tissues. However, the difficulties to distinguish malignant from normal tissue on CT slides often leads to inaccurate outlining of the GTV and/or to geographic misses. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has shown an increase in both sensitivity and specificity over CT in locoregional staging of patients with non-small cell lung cancer (NSCLC). The co registration of FDG-PET images to the data of the CT planning offers the radiation oncologist the possibility to include functional information into the target outlining. For the treatment of patients with NSCLC, it has been shown that the use of FDG-PET images: 1) modified the shape and volume of radiation fields in 22-62% of cases, mainly due to a better nodal staging and distinction of atelectasis from tumor and; 2) significatively reduced the interobserver and intraobserver variability. This paper reviews the results reported in the literature. Challenges and proposed solutions are discussed.     

Impact of computed tomography (CT) and 18F-deoxyglucose positron emission tomography (FDG-PET) image fusion for conformal radiotherapy in esophageal carcinoma]

PURPOSE: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma. PATIENTS AND METHODS: Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due to reduction of the length of the esophageal tumor. The GTV increase was >or=25% with FDG-PET in 2 patients due to the detection of occult mediastinal lymph node involvement in one patient and an increased length of the esophageal tumor in the other patient. Modifications of the GTV affected the planning treatment volume (PTV) in 18 patients. Modifications of delineation of GTV and displacement of the isocenter of PTV by FDG-PET also affected the percentage of total lung volume receiving more than 20 Gy (VL20) in 25 patients (74%), with a dose reduction in 12 patients and a dose increase in 13 patients. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of patients with esophageal carcinoma related to modifications of GTV. The impact on treatment outcome remains to be demonstrated.     

Role of FDG-PET in the diagnosis and treatment of colorectal liver metastases

Positron emission tomography (PET) using [¹⁸F]-2-deoxy-2-fluoro-d-glucose (FDG) has emerged as a promising diagnostic modality in recurrent colorectal cancer. Data in the literature show that the addition of FDG-PET changes disease management in up to 30% of patients with potentially resectable liver metastases, mainly by detecting previously unknown extrahepatic disease. Furthermore, FDG-PET is useful in the follow-up of patients who underwent surgical procedures of the liver, since it is exquisitely sensitive in detecting residual or relapse malignancy in scarred liver tissue following both resection and local ablative techniques. For follow-up during systemic therapy, early FDG-PET appears predictive for response to therapy. However, at present, the available data are insufficient to justify the FDG-PET-driven management of patients treated with chemotherapy. FDG-PET and computerized tomography are complimentary techniques in staging and restaging patients with advanced colorectal cancer. The combination of these two modalities significantly impacts upon patient management.     

Impact of computed tomography (CT) and 18F-deoxyglucose-coincidence detection emission tomography (FDG-CDET) image fusion for optimisation of conformal radiotherapy in non-small-cell lung cancers]

To report a retrospective study concerning the impact of fused 18F-fluorodeoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on three-dimensional conformal radiation therapy (3D-CRT) planning for patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: One hundred and one patients consecutively treated for stages I-III NSCLC were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. Images were coregistered using five fiducial markers. Target volume delineation was initially performed on the CT images and the corresponding FDG-PET data were subsequently used as an overlay to the CT data to define target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 8 patients making them ineligible for curative CRT (one patient presented some positive uptakes corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because fused CT/PET images demonstrated excessively extensive intrathoracic disease. The gross tumor volume (GTV) was decreased by CT/PET image fusion in 21 patients (23%) and was increased in 24 patients (26%). The GTV reduction was > or = 25% in 7 patients because CT/PET image fusion reduced pulmonary GTV in 6 patients (3 patients with atelectasis) and mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients due to an increase of the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Among 81 patients receiving a total dose > or = 60 Gy at ICRU point, after CT/PET image fusion, the percentage of total lung volume receiving more than 20 Gy (VL20) increased in 15 cases and decreased in 22 cases. The percentage of total heart volume receiving more than 36 Gy increased in 8 patients and decreased in 14 patients. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. After multivariate analysis, one single independent factor made significant effect of FDG/PET on the modification of the size of the GTV: tumor with atelectasis (P = 0.0001). Conclusion. - Our study confirms that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of patients with NSCLC. FDG images using dedicated PET scanners with modern image fusion techniques and respiration-gated acquisition protocols could improve CT/PET image coregistration. However, prospective studies with histological correlation are necessary and the impact on treatment outcome remains to be demonstrated.     

Follow-up with 18FDG-PET–CT after radical radiotherapy with or without chemotherapy allows the detection of potentially curable progressive disease in non-small cell lung cancer patients: A prospective study

BackgroundFollow-up of patients treated with curative intent for non-small cell lung cancer (NSCLC) with X-ray or CT-scans is of unproven value. Furthermore, most patients with progressive disease present with symptoms outside of follow-up visits. Because the accuracy of ¹⁸FDG-PET–CT is superior to CT, we hypothesised that FDG-PET–CT scans 3 months post-treatment could lead to early detection of progressive disease (PD) amenable for radical treatment.Patients and methodsHundred patients with NSCLC, treated with curative intent with (chemo) radiation, were prospectively evaluated. All patients underwent a planned FDG-PET–CT scan 3 months after the start of radiotherapy.ResultsTwenty four patients had PD 3 months post-treatment. 16/24 patients were symptomatic. No curative treatment could be offered to any of these patients. In 3/8 asymptomatic patients progression, potentially amenable for radical therapy was found, which were all detected with PET, not with CT only.ConclusionsPET-scanning after curative treatment for NSCLC led to the detection of progression potentially amenable for radical treatment in a small proportion (3%) of patients. Selectively offering a PET–CT scan to the patient group without symptoms could possibly lead to an effective follow-up method.     

Impact of fluorine-18 fluorodeoxyglucose positron emission tomography on patient management: first year's experience in a clinical center.

PURPOSE: To measure the impact of whole-body fluorodeoxyglucose (FDG) positron emission tomography (PET) on patient management during its first year of use in a community hospital. MATERIALS AND METHODS: First-year FDG-PET impact was determined from 463 referring physicians' evaluations of their patients' PET imaging results using two surveys. Survey 1 was given to all physicians referring patients to PET to discover whether PET changed patient management or had decision-making value in the patient's clinical algorithm. Survey 2 was given to one surgeon and one pulmonologist after therapy to determine how PET affected the surgical, chemotherapeutic, and/or radiotherapeutic treatment for the 53 cancer patients they referred. RESULTS: The 463 responses to survey 1 described 23 different PET indications. Lung (40%), head and neck (18%), and colorectal cancers (11%) were the three leading causes of referral. PET changed patient management/therapy in 45% of all patients referred and had inferential/decision-making value in another 44%. Overall, PET had some type of positive influence in 412 (89%) of the patients. Survey 2 provided a more detailed assessment of 53 referrals from two specialists. PET positively affected surgery in 31 patients (58%), prompted the addition of chemotherapy or radiation therapy in nine patients (17%), and eliminated chemotherapy or radiation therapy in four cases (8%). Overall, PET affected patient management/therapy in 70% of the cases and had some decision-making value in another 26%, for a combined PET impact on patient management of 96%. CONCLUSION: FDG-PET can be valuable for physicians in clinical practice. Its sensitivity and specificity in metabolic imaging, when combined with complementary anatomic imaging techniques, contribute significantly to the clinical treatment of cancer patients. In addition, the high accuracy of FDG-PET makes it a cost-effective radiologic procedure in the work-up of all suspected and/or recurrent cancer patients. Further research is needed to link this demonstrated impact on patient management to cost-effectiveness.     

Successfully resected stage IIIA non-small cell lung cancer with mediastinal lymphnode metastasis after chemotherapy of cisplatin and docetaxel combined with concurrent radiation

A 47-year-old man with no symptoms was admitted to our hospital for the treatment of NSCLC, which was incidentally detected by an X-ray examination at the mass screening. Computed tomography (CT) of the chest and FDG-PET revealed a 3.6 cm tumor in the right upper lobe with multiple lymphadenopathy in the right mediastinum. Based on these clinical findings, we classified this case as a T2N2M0, stage IIIA NSCLC. The patient consented to and received 2 courses of systemic chemotherapy consisting of cisplatin (CDDP 40 mg/m(2); day 1, 8) and docetaxel (DOC 40 mg/m(2); day 1, 8) combined with concurrent radiation (2 Gy/day; total 46 Gy) with no severe adverse events. His tumors responded well to the treatment, and restaging chest CT showed marked regression of mediastinal lymphadenopathy, and partial response to the lung tumor. Then, acurative surgical resection was performed. Finally, the case was diagnosed as a T1N1M0, stage IIA NSCLC pathologically. Our chemotherapy regimen consisting of CDDP and DOC combined with concurrent radiation might be as potent as neo-adjuvant therapy for clinical stage III NSCLC.     

18F-fluoro-2-deoxy-D-glucose positron emission tomographic imaging: recent developments in head and neck cancer

PURPOSE OF REVIEW: Positron emission tomography using 18F-fluoro-2-deoxy-D-glucose (18FDG-PET) is well established in clinical routine as a metabolism-based whole-body imaging tool for cancer diagnosis and follow-up. Several reports have appeared indicating the potential and limitations of this technique in head and neck cancer (HNC). This review limits its scope to the recent advances using 18FDG-PET in the clinical management of HNC. RECENT FINDINGS: The combination of 18FDG-PET and sentinel node biopsy has been explored for the surgical treatment planning of oral and oropharyngeal cancer. Recent reports indicate that multimodality imaging combining PET with high-end CT scanning increases the diagnostic accuracy. 18FDG-PET has a potential for use in radiation treatment planning and for the prediction of response and early evaluation of treatment efficacy. SUMMARY: Increasingly 18FDG-PET is used as a clinical imaging modality in the different stages of the management of HNC. In particular, its clinical value in initial staging of neck lymph nodes and in the evaluation of recurrent or residual disease is well established. In these settings 18FDG-PET has been shown to be more accurate than conventional imaging. Recent studies indicate that 18FDG-PET could be of additional value in staging the N0 neck, in radiation treatment planning, and in prediction of treatment efficacy.     

PET-CT fusion in radiation management of patients with anorectal tumors

PURPOSE: To compare computed tomography (CT) with positron emission tomography-CT (PET-CT) scans with respect to anorectal tumor volumes, correlation in overlap, and influence on radiation treatment fields and patient care. PATIENTS AND METHODS: From March to November 2003, 20 patients with rectal cancer and 3 patients with anal cancer were treated with preoperative or definitive chemoradiation, respectively. Computed tomography simulation data generated a CT gross tumor volume (CT-GTV) and CT planning target volume (CT-PTV) and (18)F-fluoro-2-deoxy-glucose PET (FDG-PET) created a PET-GTV and PET-PTV. The PET-CT and CT images were fused using manual coregistration. Patients were treated with three-dimensional conformal therapy to traditional doses. The PET, CT, and overlap volumes (OVs) were measured in cubic centimeters. RESULTS: Mean PET-GTV was smaller than the mean CT-GTV (91.7 vs. 99.6 cm(3)). The mean OV was 46.7%. As tumor volume increased, PET and CT OV correlated significantly (p < 0.001). In 17% of patients PET-CT altered the PTV, and in 26% it changed the radiation treatment plan. For 25% of patients with rectal cancer, PET detected distant metastases and changed overall management. Ten rectal cancer patients underwent surgery. When the pretreatment PET standardized uptake value was >10 and the posttreatment PET standardized uptake value was <6, 100% achieved pathologic downstaging (p = 0.047). CONCLUSIONS: Variation in volume was significant, with 17% and 26% of patients requiring a change in treatment fields and patient management, respectively. Positron emission tomography can change the management for anorectal tumors by early detection of metastatic disease or disease outside standard radiation fields.     

Clinical utility of integrated positron emission tomography/computed tomography imaging in the clinical management and radiation treatment planning of locally advanced rectal cancer

PurposeThe role of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in the staging and radiation treatment planning of locally advanced rectal cancer is ill defined. We studied the role of integrated PET/CT in the staging, radiation treatment planning, and use as an imaging biomarker in rectal cancer patients undergoing multimodality treatment.Methods and materialsThirty-four consecutive patients with T3-4N0-2M0-1 rectal adenocarcinoma underwent FDG-PET/CT scanning for staging and radiation treatment planning. Planned clinical management was compared before and after the addition of PET/CT information. Three radiation oncologists independently delineated CT-based gross tumor volumes (GTVCT) using clinical information and CT imaging data, as well as gradient autosegmented PET/CT-based GTVs (GTV_PETCT). The mean GTV, interobserver concordance index (CCI), and proximal and distal margins were compared. The maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), and dual-time point PET parameters were correlated with clinicopathologic endpoints.ResultsClinical management was altered by PET/CT in 18% (n = 6) of patients with clinical upstaging in 6 patients and radiation treatment planning altered in 5 patients. Of the 30 evaluable preoperative patients, the mean GTV_PETCT was significantly smaller than the mean GTV_CT volumes: 88.1 versus 102.8 cc (P = .03). PET/CT significantly increased interobserver CCI in contouring GTV compared with CT only-based contouring: 0.56 versus 0.38 (P < .001). The proximal and distal margins were altered by a mean of 0.4 ± 0.24 cm and −0.25 ± 0.18 cm, respectively. MTV was inversely associated with 2-year progression-free survival (PFS) and overall survival (OS): smaller MTVs (< 33 cc) had superior 2-year PFS (86% vs 60%, P = .04) and OS (100% vs 45%, P < .01) compared with larger MTVs (> 33 cc). SUVmax and dual-time point PET parameters did not correlate with any endpoints.ConclusionsFDG-PET/CT imaging impacts overall clinical management and is useful in the radiation treatment planning of rectal cancer patients by decreasing interobserver variability in contouring target boost volumes. Pretreatment MTV may provide useful prognostic information and requires further study.     

The role of positron emission tomography in management of small cell lung cancer

Accurate radiological staging of small-cell lung cancer (SCLC) is of paramount importance in selection of individual patients with limited stage disease for potentially curative treatment while avoiding toxic treatment in those with distant metastatic disease. [¹⁸F] flurodeoxy-d-glucose (FDG) positron emission tomography (PET) is an attractive tool for this purpose but there is limited evidence to support its use in the routine staging of SCLC. Whether therapeutic decisions based on FDG-PET imaging should be made remains uncertain. There is only preliminary evidence for use of FDG-PET as a prognostic biomarker, in the assessment of response to treatment and delineation of disease in conformal radiation planning.     

Impact of hybrid fluorodeoxyglucose positron-emission tomography/computed tomography on radiotherapy planning in esophageal and non-small-cell lung cancer

PURPOSE: The aim of this study was to investigate the impact of a hybrid fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) scanner in radiotherapy planning for esophageal and non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: A total of 30 patients (16 with esophageal cancer, 14 with NSCLC) underwent an FDG-PET/CT for radiotherapy planning purposes. Noncontrast total-body spiral CT scans were obtained first, followed immediately by FDG-PET imaging which was automatically co-registered to the CT scan. A physician not involved in the patients' original treatment planning designed a gross tumor volume (GTV) based first on the CT dataset alone, while blinded to the FDG-PET dataset. Afterward, the physician designed a GTV based on the fused PET/CT dataset. To standardize PET GTV margin definition, background liver PET activity was standardized in all images. The CT-based and PET/CT-based GTVs were then quantitatively compared by way of an index of conformality, which is the ratio of the intersection of the two GTVs to their union. RESULTS: The mean index of conformality was 0.44 (range, 0.00-0.70) for patients with NSCLC and 0.46 (range, 0.13-0.80) for patients with esophageal cancer. In 10 of the 16 (62.5%) esophageal cancer patients, and in 12 of the 14 (85.7%) NSCLC patients, the addition of the FDG-PET data led to the definition of a smaller GTV. CONCLUSION: The incorporation of a hybrid FDG-PET/CT scanner had an impact on the radiotherapy planning of esophageal cancer and NSCLC. In future studies, we recommend adoption of a conformality index for a more comprehensive comparison of newer treatment planning imaging modalities to conventional options.     

Posttreatment assessment of response using FDG-PET/CT for patients treated with definitive radiation therapy for head and neck cancers

PURPOSE: The goal of this study was to evaluate coregistered [18F] fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) for the detection of persistent disease after definitive radiation therapy in head and neck cancer. METHODS AND MATERIALS: Posttreatment FDG-PET/CT was performed in 28 patients on average 8 weeks (range, 4 to 15.7 weeks) after completing definitive radiation therapy. FDG-PET/CT was visually analyzed for the entire patient group and at two time points (4-8 and >8 weeks) after treatment. The contrast-enhanced CT portion of PET/CT was separately analyzed blinded to the results of coregistered FDG-PET/CT and classified as negative or positive for residual locoregional disease. Pathologic findings and clinical follow-up served as the reference standard. RESULTS: Follow-up data were available for all 28 patients (median, 17.6 months). Regarding the detection of residual disease, the overall sensitivity and specificity of FDG-PET/CT was 76.9% and 93.3%, respectively, compared with 92.3% and 46.7% for contrast-enhanced CT. The accuracy of FDG-PET/CT was 85.7%, compared with 67.9% for CT alone. All false-negative (n = 3) and false-positive (n = 1) FDG-PET/CT results occurred between 4 and 8 weeks after treatment. At 8 weeks or later after treatment, the specificity of CT was 28%, compared with 100% for FDG-PET/CT. CONCLUSIONS: The metabolic-anatomic information from coregistered FDG-PET/CT provided the most accurate assessment for treatment response when performed later than 8 weeks after the conclusion of radiation therapy. FDG-PET/CT excelled by a higher specificity and overall diagnostic performance than CT imaging alone. These results support a potential clinical role of FDG-PET/CT in the early assessment of therapy response after definitive radiation therapy.     

PET-CT in the staging and treatment of non-small-cell lung cancer

Positron emission tomography with 2-(¹⁸F)-fluoro-2-deoxy-D-glucose (FDG-PET) is a metabolic imaging technique. FDG-PET is more accurate than CT for the evaluation of mediastinal involvement in patients with nonsmall-cell lung cancer, offering a high negative predictive value. It can detect occult metastases in 11% of patients, although the etiology of the extrathoracic isolated uptakes needs confirmation. Theoretically, FDG-PET can influence the planning volume for radiotherapy, primarily in patients with atelectasis. Quantification of metabolic activity using FDG-PET is influenced by the size of the lesion, glucose levels and the time elapsed since the isotope injection. More clinical trials are required to standardize the methods for performing PET, assess its use as a prognostic factor and for the evaluation of treatment response.     

Dosimetric implications of the addition of 18 fluorodeoxyglucose-positron emission tomography in CT-based radiotherapy planning for non-small-cell lung cancer

The aim of this study was to assess the impact of F-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) CT on radiotherapy planning parameters for patients treated curatively with radiotherapy for non-small-cell lung cancer (NSCLC). Five patients with stages I–III NSCLC underwent a diagnostic FDG-PET CT (dPET CT), planning FDG-PET CT (pPET CT) and a simulation CT (RTP CT). For each patient, three radiation oncologists delineated a gross tumour volume based on RTP CT alone, and fused with dPET CT and pPET CT. Standard expansions were used to generate PTVs, and a 3D conformal plan was created. Normal tissue doses were compared between plans. Coverage of pPET CT PTV by the plans based on RTP CT and dPET CT was assessed, and tumour control probabilities were calculated. Mean PTV was similar between RTP CT, dPET CT and pPET CT, although there were significant inter-observer differences in four patients. The plans, however, showed no significant differences in doses to lung, oesophagus, heart or spinal cord. The RTP CT plan and dPET CT plan significantly underdosed the pPET PTV in two patients with minimum doses ranging from 12 to 63% of prescribed dose. Coverage by the 95% isodose was suboptimal in these patients, but this did not translate into poorer tumour control probability. The effect of fused FDG-PET varied between observers. The addition of dPET and pPET did not significantly change the radiotherapy planning parameters. Although FDG-PET is of benefit in tumour delineation, its effect on normal tissue complication probability and tumour control probability cannot be predicted.     

FDG-PET scans in patients with lymphoma

Lymphoma comprises a complex set of diseases, including Hodgkin and non-Hodgkin subtypes. An expected goal of management is chronic disease control over decades in most patients with indolent subtypes, and cure is a realistic target for aggressive histologies, including Hodgkin lymphoma. Making methods available to better assess prognosis and to more specifically tailor therapy toward individual subtypes is a priority. Positron emission tomography using the tracer ¹⁸fluoro-2-deoxyglucose (FDG-PET) has become a valuable tool in the care of patients with lymphoma; it contributes information on staging and response assessment that has the potential to affect and improve patient care. This imaging modality is also being explored as an early response assessor, potentially allowing early prediction of an individual’s response to a specific therapy. This information ultimately may lead to modifications of treatment to improve efficacy or reduce toxicity. Although FDG-PET offers valuable information, it is important to recognize its limitations as well as areas that require further exploration in order to optimally integrate its use into the clinical management of lymphoma patients.     

An evidence-based review on the value of interim FDG-PET in assessing response to therapy in lymphoma

Assessing response to therapy in lymphoma is important for determining patients’ prognosis, guiding subsequent treatment, and may be used as an outcome measure of prognostic and therapeutic trials. Traditionally, computed tomography was the mainstay for response assessment and was predominantly performed at the end of treatment, whereas the most recent guidelines propose ¹⁸F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) for this purpose. However, the value of FDG-PET performed during treatment (interim FDG-PET) is still a topic of debate. The purpose of this scientific communication is to provide an evidence-based overview of the value of interim FDG-PET in patients with lymphoma. The article first describes the development of imaging-based response assessment in lymphoma, the rationale and limitations of using FDG-PET for this purpose, and continues with the evidence-based clinical utility of interim FDG-PET in three major lymphoma subtypes (Hodgkin lymphoma, diffuse large B-cell lymphoma, and follicular lymphoma), and finishes with conclusions and recommendations for standard care and future research.