Serial Evaluation of Increased Chest Wall F-18 Fluorodeoxyglucose (FDG) Uptake Following Radiation Therapy in Patients With Bronchogenic Carcinoma

Clinical Positron Imaging

Volume 1, Issue 3, Summer 1998, Pages 185-191

Abstract

Purpose: Following radiation therapy for bronchogenic carcinoma, increased FDG accumulation within the irradiated tissue can be identified. This finding has not been well characterized. Therefore, we retrospectively evaluated the time course, frequency, and intensity of increased FDG uptake over a one-year period in patients who had been treated with radiation therapy. Materials and Methods: Serial FDG-PET studies (n = 38) were performed in patients (n = 12) with bronchogenic carcinoma before and after radiation therapy. Regions of interest (ROIs) were placed in the chest wall and activity concentrations of posttherapy studies were compared to pretherapy studies. FDG uptake was also described qualitatively relative to mediastinal activity (1–4 scale) by two observers blinded from clinical information. Results: Chest wall radiation port ROI uptake was 18% higher in the 2-month (P = 0.08), 40% higher in the 6-month (P = 0.003), and 32% higher in the 12-month (P = 0.04) posttherapy studies than in non-port ROIs. In 6 patients that clinically had radiation-induced chest wall fibrosis or pneumonitis, visual interpretation identified abnormal chest wall or pleural region FDG uptake in 5/6. In 2/6 patients without clinical chest wall fibrosis, abnormal, chest wall FDG uptake was seen. Conclusions: Radiation therapy occasionally causes modestly increased soft tissue FDG uptake within irradiated soft tissue in patients being treated for bronchogenic carcinoma, which persists for up to one year after therapy.

Introduction

Radiation therapy has been the treatment of choice for patients with unresectable non-small cell lung cancer. Such patients who have typically been treated with doses of 6,000–7,000 rad have a median survival of 12 months and patients with all types of lung cancer have a 5-year survival of 5–10%.1, 2 The local control rates achieved in such patients have been difficult to assess but are generally poor.³ These results have prompted efforts to improve local control, and possibly survival, through dose escalation.⁴ The accurate assessment of the therapeutic effect of chemotherapy and radiation therapy is of great importance if survival from lung cancer is to be improved. A typical radiation dose for treating non-small cell carcinoma is 6,000 rads. Few patients are cured by this dose. If the incomplete responders without metastases could be identified, escalating the radiation dose could be considered.

Anatomic imaging is of little help in evaluating the effect of radiation or chemotherapy.⁵ The pulmonary changes from persistent tumor, scarring, atelectasis, and necrosis after therapy cannot be differentiated by CT or MRI. Tumor size can decrease after therapy but may not be an accurate indicator of tumor response. Tissue biopsy is subject to sampling error.

Increased glucose metabolism is a well-described property of malignant tumor cells,6, 7, 8 and several studies have demonstrated the utility of positron emission tomography (PET) and F-18 fluorodeoxyglucose (FDG) in distinguishing benign from malignant abnormalities in the thorax9, 10 and in identifying tumor recurrence.11, 12

In evaluating tumor recurrence in patients who have received radiation therapy, we occasionally identify increased FDG uptake in thoracic structures presumably due to the inflammatory reaction following radiation therapy. Studies have shown increased FDG accumulation at the sties of infection or inflammation.9, 10, 11, 12, 13 Presumably, increased FDG accumulation will diminish after completion of radiation therapy with diminution of inflammation. The time course or duration of increased FDG uptake following radiation therapy has not been described and is important in the evaluation of recurrent disease. We, therefore, retrospectively evaluated serial FDG-PET studies to determine the time course, frequency, and intensity of increased FDG uptake over a one-year period in patients who had been treated with radiation.

Section snippets

Patients

Patients (n = 12) with bronchogenic carcinoma who were to received radiation therapy (average dose = 7,101 ± 465 rads) were referred for evaluation by FDG-PET. FDG-PET studies (n = 38) were performed before and serially after radiation therapy in all patients as part of other FDG-PET/radiation therapy protocols. Posttherapy studies were performed at 2 months (mean = 70 ± 30 days) in 9 patients, 6 months (mean = 195 ± 47 days) in 11 patients, and 12 months (mean = 342 ± 102 days) in 5 patients.

Results

Chest wall ROI uptake in the irradiated regions was 18% higher in the 2-month (P = 0.08), 40% higher in the 6-month (P = 0.003), and 32% higher in the 12-month (P = 0.04) posttherapy studies than in non-port ROIs Figure 2, Figure 3. The mean standardized uptake ratio (SUR) for the 7 patients with increased FDG uptake (from selected port regions with the most uptake) was 1.8 ± 0.6. Two patients showed SURs of 2.5 or greater (2.6 and 2.6).

No patients had clinical evidence of metastatic disease to

Discussion

In this report, we describe patients treated with radiation therapy for bronchogenic carcinoma who had serial FDG-PET studies. FDG-PET imaging may be a valuable tool in the treatment of patients with locally advanced lung cancer. FDG-PET could possibly assist in radiation therapy planning by focusing radiation fields to precise areas of tumor activity, preventing both irradiation of uninvolved areas and omission of regions of active tumor from radiation ports. FDG-PET imaging also provides

Conclusion

Patients evaluated with FDG-PET for recurrence of bronchogenic carcinoma after having received radiation therapy may have abnormal FDG uptake in radiation port regions that can persist for at least one year after therapy and is probably due to inflammation and tissue regeneration. The uptake is generally of minimal intensity but in a few cases may be similar to that seen with malignant disease. Review of radiation port locations is recommended in the evaluation of FDG-PET data in these patients.

Acknowledgements

The authors wish to thank Thomas C. Hawk for his dedication in performing the ROI measurements for this study.

References (15)

D.G. Bragg
Current applications of imaging procedures in the patient with lung cancer
Int. J. Radiat. Oncol. Biol. Phys.
(1991)
G.L. Becker et al.
The impact of thoracic computed tomography in clinically staged T1, N0, M0 chest lesions
Arch. Intern. Med.
(1990)
D. Recine et al.
Combined modality therapy for locally advanced non-small cell lung carcinoma
Cancer
(1990)
R.J. Ginsberg et al.
Cancer of the Lung
J.D. Cox et al.
A randomized phase I/II trial of hyperfractionated radiation therapy with total doses of 60.0 Gy to 79.2 Gy. Possible survival benefit with > 69.9 Gy in favorable patients with Stage III non-small cell lung cancerReport of Radiation Therapy Oncology Group 83-11
J. Clin. Oncol.
(1990)
O. Warburg
The metabolism of tumors
(1930)
G. Weber
Enzymology of cancer cells. Part I
N. Engl. J. Med.
(1977)

There are more references available in the full text version of this article.

Cited by (18)

PET imaging of head and neck cancer
2022, Nuclear Medicine and Molecular Imaging: Volume 1-4
Head and neck cancers (HNC) are the sixth most common cancer worldwide. An estimated 630,000 patients are diagnosed annually, resulting in more than 350,000 deaths annually. The advent of positron emission tomography (PET) has improved the staging, treatment evaluation, and detection of recurrent disease in patients with HNSCC’s. The role of PET/CT in oncology has revolutionized our understanding and ability to diagnose and treat HNC’s. As with any modality limitations exist and these can only be addressed through more extensive research. Learning the anatomical landmarks and the distinction between normal and abnormal FDG physiologic uptake patterns will ensure that radiologists and nuclear medicine physicians make accurate decisions at all stages of patient care.
PET/CT Variants and Pitfalls in Head and Neck Cancers Including Thyroid Cancer
2021, Seminars in Nuclear Medicine
Citation Excerpt :
FDG uptake is increased in recently irradiated tissues and is more intense in tissues that received a higher radiation dose. The increased uptake can last for 12-16 months post radiotherapy.165 Overlap in the SUVmax values demonstrated in radiation related inflammatory change and that of recurrent disease can lead to diagnostic uncertainty, particularly early on (less than 2 months post therapy).166,167
PET/CT imaging is a dual-modality diagnostic technology that merges metabolic and structural imaging. There are several currently available radiotracers, but ¹⁸F-FDG is the most commonly utilized due to its widespread availability. ¹⁸F-FDG PET/CT is a cornerstone of head and neck squamous cell carcinoma imaging. ⁶⁸Ga-DOTA-TOC is another widely used radiotracer. It allows for whole-body imaging of cellular somatostatin receptors, commonly expressed by neuroendocrine tumors and is the standard of reference for the characterization and staging of neuroendocrine tumors.
The normal biodistribution of these PET radiotracers as well as the technical aspects of image acquisition and inadequate patient preparation affect the quality of PET/CT imaging. In addition, normal variants, artifacts and incidental findings may impede accurate image interpretation and can potentially lead to misdiagnosis. In order to correctly interpret PET/CT imaging, it is necessary to have a comprehensive knowledge of the normal anatomy of the head and neck and to be cognizant of potential imaging pitfalls. The interpreter must be familiar with benign conditions which may accumulate radiotracer potentially mimicking neoplastic processes and also be aware of malignancies which can demonstrate low radiotracer uptake.
Appropriate use of structural imaging with either CT, MR or ultrasound can serve a complimentary role in several head and neck pathologies including local tumor staging, detection of bone marrow involvement or perineural spread, and classification of thyroid nodules. It is important to be aware of the role of these complementary modalities to maximize diagnostic accuracy and patient outcomes.
The purpose of this article is to outline the basic principles of PET/CT imaging, with a focus on ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA PET/CT. Basic physiology, variant imaging appearances and potential pitfalls of image interpretation are presented within the context of common use cases of PET technology in patients with head and neck cancers and other pathologies, benign and malignant.
Role of 18F-FDG-PET/CT in evaluation of carcinoma epidermoid of head and neck. Lebanese experience with review of the literature
2015, Medecine Nucleaire
Depuis son application dans l’évaluation et le suivi des cancers épidermoïdes de la tête et du cou, la TEP/TDM est devenue la modalité d’imagerie de choix pour cette catégorie fournissant des informations anatomiques et métaboliques à la fois. La 18F-FDG-TEP/TDM est utile dans l’identification d’un primitif non déjà connu, la délimitation de l’extension de la tumeur primitive, la détection d’une atteinte ganglionnaire régionale même avec des ganglions de petite taille, la détection d’une atteinte métastatique à distance et parfois dans la détection d’un second primitif synchrone. Elle assure un rôle primordial dans l’évaluation de la réponse au traitement, dans le suivi de la récurrence à long terme et récemment dans la planification de la radiothérapie.
Since its implementation in the evaluation and monitoring of squamous cell carcinoma of the head and neck, PET/CT has become the imaging modality of choice for this category providing anatomical and metabolic information at once. 18F-FDG-PET/CT is useful in identifying a cancer of unknown primary, extension of the primary tumor, detection of regional lymph node involvement even with infracentimetric lymph node, detecting a metastatic lesion and in few instances identifying a synchronous primitive tumor. It provides a vital role in assessing the response to treatment, monitoring the long-term recurrence and recently in planning radiotherapy.
Non-Small Cell Lung Cancer
2015, Clinical Radiation Oncology
Non-Small Cell Lung Cancer
2012, Clinical Radiation Oncology: Third Edition
Non–Small Cell Lung Cancer
2011, Clinical Radiation Oncology, Third Edition

View all citing articles on Scopus

View full text

ORIGINAL ARTICLESerial Evaluation of Increased Chest Wall F-18 Fluorodeoxyglucose (FDG) Uptake Following Radiation Therapy in Patients With Bronchogenic Carcinoma

Abstract

Introduction

Section snippets

Patients

Results

Discussion

Conclusion

Acknowledgements

Int. J. Radiat. Oncol. Biol. Phys.

The impact of thoracic computed tomography in clinically staged T1, N0, M0 chest lesions

Arch. Intern. Med.

Combined modality therapy for locally advanced non-small cell lung carcinoma

Cancer

Cancer of the Lung

A randomized phase I/II trial of hyperfractionated radiation therapy with total doses of 60.0 Gy to 79.2 Gy. Possible survival benefit with > 69.9 Gy in favorable patients with Stage III non-small cell lung cancerReport of Radiation Therapy Oncology Group 83-11

J. Clin. Oncol.

The metabolism of tumors

Enzymology of cancer cells. Part I

N. Engl. J. Med.

ORIGINAL ARTICLE
Serial Evaluation of Increased Chest Wall F-18 Fluorodeoxyglucose (FDG) Uptake Following Radiation Therapy in Patients With Bronchogenic Carcinoma