Role of positron emission tomography in the management of head and neck cancer in the molecular therapy era

F-18 fluoromisonidazole for imaging tumor hypoxia: imaging the microenvironment for personalized cancer therapy

Hypoxia in solid tumors is one of the seminal mechanisms for developing aggressive trait and treatment resistance in solid tumors. This evolutionarily conserved biological mechanism along with derepression of cellular functions in cancer, although resulting in many challenges, provide us with opportunities to use these adversities to our advantage. Our ability to use molecular imaging to characterize therapeutic targets such as hypoxia and apply this information for therapeutic interventions is growing rapidly. Evaluation of hypoxia and its biological ramifications to effectively plan appropriate therapy that can overcome the cure-limiting effects of hypoxia provides an objective means for treatment selection and planning. Fluoromisonidazole (FMISO) continues to be the lead radiopharmaceutical in PET imaging for the evaluation, prognostication, and quantification of tumor hypoxia, one of the key elements of the tumor microenvironment. FMISO is less confounded by blood flow, and although the images have less contrast than FDG-PET, its uptake after 2 hours is an accurate reflection of inadequate regional oxygen partial pressure at the time of radiopharmaceutical administration. By virtue of extensive clinical utilization, FMISO remains the lead candidate for imaging and quantifying hypoxia. The past decade has seen significant technological advances in investigating hypoxia imaging in radiation treatment planning and in providing us with the ability to individualize radiation delivery and target volume coverage. The presence of widespread hypoxia in the tumor can be effectively targeted with a systemic hypoxic cell cytotoxin or other agents that are more effective with diminished oxygen partial pressure, either alone or in combination. Molecular imaging in general and hypoxia imaging in particular will likely become an important in vivo imaging biomarker of the future, complementing the traditional direct tissue sampling methods by providing a snap shot of a primary tumor and metastatic disease and in following treatment response and will serve as adjuncts to personalized therapy.

Assessment of hypoxic subvolumes in laryngeal cancer with (18)F-fluoroazomycinarabinoside ((18)F-FAZA)-PET/CT scanning and immunohistochemistry

BACKGROUND AND PURPOSE

(18)F-fluoroazomycinarabinoside ((18)F-FAZA) is a promising hypoxia radiopharmaceutical agent with outstanding biokinetic parameters. We aimed to determine the accuracy of (18)F-FAZA-PET/CT scan in detecting hypoxic regions within the tumor using immunohistochemical markers in a pilot study.

PATIENTS AND METHODS

Eleven patients with primary or recurrent laryngeal squamous cell carcinoma were indicated for total laryngectomy (TLE). Patients underwent (18)F-FAZA-PET/CT scan before TLE. Hypoxic regions inside the laryngeal tumor were determined. After TLE, regions with high uptake on (18)F-FAZA-PET scan were selected for immunohistochemical examination for exogenous (pimonidazole) and endogenous (HIF1α, CA-IX and GLUT-1) hypoxia markers. To assess the accuracy of (18)F-FAZA-PET scanning, radiopharmacon accumulation was related with immunohistochemical expression of hypoxia markers.

RESULTS

Inter- and intratumoral heterogeneity of tumor hypoxia was observed on (18)F-FAZA-PET scan. Nine of the eleven tumors were hypoxic with (18)F-FAZA-PET. Hypoxia could also be detected with pimonidazole, HIF1α, CA-IX and GLUT-1 expression in some tumors. No clear association was observed between (18)F-FAZA uptake and hypoxia markers.

CONCLUSIONS

This pilot study could not prove the accuracy of (18)F-FAZA-PET in determining hypoxic subvolumes in laryngeal cancer. Further study is required to investigate the benefit of (18)F-FAZA-PET imaging in radiotherapy planning.

Head and neck tumor hypoxia imaging by 18F-fluoroazomycin-arabinoside (18F-FAZA)-PET: a review

Tumor hypoxia is known to be associated with poor clinical outcome; therefore, patients with hypoxic tumors might benefit from more intensive treatment approaches. This is particularly true for patients with head and neck cancer. Pretreatment assessment of hypoxia in tumors would be desirable, not only to predict prognosis but also to select patients for more aggressive treatment.As an alternative to the invasive polarographic needle electrode method, there is the possibility of using PET with radiopharmaceuticals visualizing hypoxia. Most hypoxia imaging studies on head and cancer have been performed using F-labeled fluoromisonidazole (F-FMISO). A chemically related molecule, F-fluoroazomycin-arabinoside (F-FAZA), seems to have superior kinetic properties and may therefore be the radiopharmaceutical of choice.This minireview summarizes the published literature on animal and human F-FAZA PET studies. Furthermore, future perspectives on how individualized treatment could be applied in patients with hypoxic head and neck tumors are discussed, for instance, the use of hypoxia sensitizers or special intensity-modulated radiation therapy techniques achieving tumor subvolume dose escalation.

¹⁸F-FDG-PET imaging in radiotherapy tumor volume delineation in treatment of head and neck cancer

PURPOSE

To determine the impact of (18)F-fluorodeoxyglucose positron emission tomography (PET) in radiotherapy target delineation and patient management for head and neck squamous cell carcinoma (HNSCC) compared to computed tomography (CT) alone.

MATERIALS AND METHODS

Twenty-nine patients with HNSCC were included. CT and PET/CT obtained for treatment planning purposes were reviewed respectively by a neuroradiologist and a nuclear medicine specialist who were blinded to the findings from each other. The attending radiation oncologist together with the neuroradiologist initially defined all gross tumor volume of the primary (GTVp) and the suspicious lymph nodes (GTVn) on CT. Subsequently, the same radiation oncologist and the nuclear medicine specialist defined the GTVp and GTVn on (18)F-FDG-PET/CT. Upon disagreement between CT and (18)F-FDG-PET on the status of a particular lymph node, an ultrasound-guided fine needle aspiration was performed. Volumes based on CT and (18)F-FDG-PET were compared with a paired Student's t-test.

RESULTS

For the primary disease, four patients had previous diagnostic tonsillectomy and therefore, FDG uptake occurred in 25 patients. For these patients, GTVp contoured on (18)F-FDG-PET (GTVp-PET) were smaller than the GTVp contoured on CT (GTVp-CT) in 80% of the cases, leading to a statistically significant volume difference (p=0.001). Of the 60 lymph nodes suspicious on PET, 55 were also detected on CT. No volume change was observed (p=0.08). Ten biopsies were performed for lymph nodes that were discordant between modalities and all were of benign histology. Distant metastases were found in two patients and one had a newly diagnosed lung adenocarcinoma.

CONCLUSIONS

GTVp-CT was significantly larger when compared to GTVp-PET. No such change was observed for the lymph nodes. (18)F-FDG-PET modified treatment management in three patients, including two for which no curative radiotherapy was attempted. Larger multicenter studies are needed to ascertain whether combined (18)F-FDG-PET/CT in target delineation can influence the main clinical outcomes.

Viable tumor in postchemoradiation neck dissection specimens as an indicator of poor outcome

BACKGROUND

The objective of this study was to determine the prognostic significance of viable tumor in postchemoradiation neck dissection specimens in patients with squamous cell carcinoma of the laryngopharynx.

METHODS

Retrospective analysis identified 181 patients treated with primary concurrent chemoradiation for carcinoma of the laryngopharynx at Memorial Sloan-Kettering Cancer Center between the years 1995 and 2005. Of these, 56 patients had a comprehensive neck dissection either as a planned or salvage procedure. Neck dissection specimens were analyzed by a single pathologist for the presence of viable tumor. The presence of viable tumor was correlated to the timing of neck dissection after chemoradiation and to tumor response. Overall survival (OS), disease-specific survival (DSS), and recurrence-free survival (RFS) were determined by the Kaplan-Meier method, and correlation to tumor viability was determined with the log-rank test.

RESULTS

Nineteen (33%) patients had viable tumor in their neck dissection specimens. Viable tumor was higher in patients who had a less-than-complete response to chemoradiation compared with those who had a complete response (42% vs 25%, p = .1). There was no correlation to timing of neck dissection. The 5-year OS, DSS, and RFS were significantly lower in patients who had viable tumor in their neck dissection specimens (OS 49% vs 93%, p = .0005; DSS 56% versus 93%, p = .003; RFS 40% vs 75%, p = .004).

CONCLUSIONS

Patients with viable tumor in postchemoradiation neck dissection specimens had a poorer outcome compared with patients with no viable tumor.

Prospective, blinded trial of whole-body magnetic resonance imaging versus computed tomography positron emission tomography in staging primary and recurrent cancer of the head and neck

Objectives:

To compare the use of computed tomography – positron emission tomography and whole-body magnetic resonance imaging for the staging of head and neck cancer.

Patients and methods:

From January to July 2009, 15 consecutive head and neck cancer patients (11 men and four women; mean age 59 years; age range 19 to 81 years) underwent computed tomography – positron emission tomography and whole-body magnetic resonance imaging for pre-therapeutic evaluation. All scans were staged, as per the American Joint Committee on Cancer tumour–node–metastasis classification, by two blinded consultant radiologists, in two sittings. Diagnoses were confirmed by histopathological examination of endoscopic biopsies, and in some cases whole surgical specimens.

Results:

Tumour staging showed a 74 per cent concordance, node staging an 80 per cent concordance and metastasis staging a 100 per cent concordance, comparing the two imaging modalities.

Conclusion:

This study found radiological staging discordance between the two imaging modalities. Whole-body magnetic resonance imaging is an emerging staging modality with superior visualisation of metastatic disease, which does not require exposure to ionising radiation.

Autofluorescence improves pretreatment mucosal assessment in head and neck cancer patients

OBJECTIVE

Panendoscopy is used in selected patients with head and neck cancer to detect second primary disease. We hypothesized that adding autofluorescence to the bronchoscopy and laryngoscopy part of this procedure could add to the detection of clinically meaningful dysplasias and carcinomas in both the head and neck and bronchus, with resultant change in management.

STUDY DESIGN

Prospective observational study on consecutive patients with head and neck cancer who had panendoscopy prior to surgery.

SETTING

Teaching hospital, tertiary referral center.

SUBJECTS AND METHODS

All patients had white-light inspection observed by ENT surgeons, followed by autofluorescence inspection of the head and neck tumor and surrounding area as well as the bronchus. Extra biopsies were taken from regions of abnormal fluorescence where there was no white-light abnormality.

RESULTS

Sixty-six patients were studied; mean age 64.9 +/- 11 years. As a result of autofluorescence, 33 mucosal biopsies were taken from the head and neck and 37 from the bronchus. Histology included three carcinoma in situ lesions and four severe dysplasias. As a result of these autofluorescence biopsies, change of management occurred in four patients (6% of the total patients). Standard panendoscopy changed management in five patients. Therefore, standard panendoscopy led to change in management in only 55 percent of cases (CI 21%-86%, P = 0.02), with the rest detected by autofluorescence.

CONCLUSION

Adding autofluorescence to panendoscopy in patients with head and neck cancer changed management in a clinically significant number of patients.

[Metabolic markers of the head and neck cancers--clinical applications and the biochemical background]

The problem of diagnosis in the field of head and neck region is still valid. Specific diagnosis and precise estimation of the tumor's size with the use of CT and MRI imaging is generally unsatisfactory. The Positron Emission Tomography (PET) supports this process with additional information about the tumor's metabolism. Numerous publications show that PET-CT has a great influence on the evaluation of the size of the tumor, presence of lymph node metastases, choice of treatment and the prognosis of the recurrence. Cancer cells represent a specific metabolic state. These cells intake large quantities of glucose and utilize it in the process of glycolysis. The oxidative phosphorylation is not efficient in the transformed cells and defects in mitochondrial functions are at the heart of malignant cell transformation. Disruption of the oxidative phosphorylation chain has been described in the neoplasms. As a consequence, in cancer the glycolysis is active even in the normoxic environment. This metabolic shift in cell transformation has been described in early XX century and so called Warburg's hypothesis profoundly influenced the present perception of cancer metabolism, positioning what is termed aerobic glycolysis in the mainstream of clinical oncology. Today we know that neoplastic cells differ at the proteomic level. A subset of different proteins such as hexokinase II or HIF are upregulated. These abnormalities might be used as the neoplastic markers.

The impact of (18)F-FDG PET-CT scanning for staging and management of Merkel cell carcinoma: results from Westmead Hospital, Sydney, Australia

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy with high mortality. Positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) has been shown to be valuable in the management of many types of cancer, and the purpose of this work was to determine its utility for patients with MCC.

OBJECTIVE

We sought to evaluate the impact of (18)F-FDG PET with simultaneous computed tomography (PET-CT) on the staging and management of patients with MCC.

METHODS

We reviewed the medical records of 18 patients with MCC who underwent 21 PET-CT scans at our institution from 2006 to 2008. The impact of PET-CT on staging and management plans were evaluated.

RESULTS

There were 12 men and 6 women with median age of 79 years (range, 54 to 85 years). All proven sites of MCC greater than 5 mm were positive on PET-CT with average maximum standardized uptake values (SUV max) of 4 in primary lesions, 5.6 in nodal disease and 11.5 in distant metastases. PET-CT contributed to altered staging in 7 patients (33%) and a change in management in 9 patients (43%). Two patients were found to have a second primary malignancy, but this did not alter management.

LIMITATIONS

This was a retrospective review. Most patients had stage II or III disease, suggesting some potential referral bias.

CONCLUSIONS

(18)F-FDG PET-CT had a high impact in the management of MCC patients in our series and this investigation merits further assessment.