Solitary pulmonary nodule and <sup>18</sup>F-FDG PET/CT. Part 2: accuracy, cost-effectiveness, and current recommendations

A solitary pulmonary nodule is a common, often incidental, radiographic finding. The investigation and differential diagnosis of solitary pulmonary nodules remain complex, because there are overlaps between the characteristics of benign and malignant processes. There are currently many strategies for evaluating solitary pulmonary nodules. The main objective is to identify benign lesions, in order to avoid exposing patients to the risks of invasive methods, and to detect cases of lung cancer accurately, in order to avoid delaying potentially curative treatment. The focus of this study was to review the evaluation of solitary pulmonary nodules, to discuss the current role of ¹⁸F-fluorodeoxyglucose positron-emission tomography, addressing its accuracy and cost-effectiveness, and to detail the current recommendations for the examination in this scenario.

Keywords:
Solitary pulmonary nodule; Positron-emission tomography

Authorship

Marcos Pretto Mosmann

MD, MSc, Nuclear Medicine Physician at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.Liga Norte-Riograndense Contra o CâncerBrazilNatal, RN, BrazilMD, MSc, Nuclear Medicine Physician at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.

Marcelle Alves Borba

MD, Radiologist at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.Liga Norte-Riograndense Contra o CâncerBrazilNatal, RN, BrazilMD, Radiologist at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.

Francisco Pires Negromonte de Macedo

Adriano de Araujo Lima Liguori

Arthur Villarim Neto

PhD, Nuclear Medicine Physician at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.Liga Norte-Riograndense Contra o CâncerBrazilNatal, RN, BrazilPhD, Nuclear Medicine Physician at Liga Norte-Riograndense Contra o Câncer, Natal, RN, Brazil.

Kenio Costa de Lima

Post Doc Fellow, Professor, Programa de Pós-Graduação em Saúde Coletiva - Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil.Universidade Federal do Rio Grande do NorteBrazilNatal, RN, BrazilPost Doc Fellow, Professor, Programa de Pós-Graduação em Saúde Coletiva - Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil.

Mailing address: Dr. Marcos Pretto Mosmann. Avenida Senador Salgado Filho, 1787, Lagoa Nova. Natal, RN, Brazil, 59056-000. E-mail: mosmann@gmail.com.

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (3)
Tables (1)

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Figure 1
A: Axial fused ¹⁸F-FDG PET/CT image. B: Axial PET image. Patient with history of epidermoid cervical carcinoma, referred for indeterminate pulmonary nodule research. Upon ¹⁸F-FDG PET/CT examination, the nodule displayed increased glycolytic metabolism (SUVmax = 5.6). She was submitted to surgery, which confirmed the hypothesis of involvement of the underlying disease.

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Figure 2
A: Axial fused ¹⁸F-FDG PET/CT image. ^B: Axial PET image. Patient with no history of cancer referred for investigation of an indeterminate pulmonary nodule. Upon ¹⁸F-FDG PET/CT examination, the pulmonary nodule showed no anomalous accumulation of the tracer.

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Figure 3
A: Axial fused ¹⁸F-FDG PET/CT image. B: Axial chest CT image. C: Axial fused ¹⁸F-FDG PET/CT image. D: PET axial image. Patient with a history of gastrointestinal stromal tumor presenting with indeterminate pulmonary nodule in the right lower lobe in a previous CT scan. Upon ¹⁸F-FDG PET/CT examination, the nodule displayed slightly increased glycolytic metabolism when compared with normal lung parenchyma (arrows in A and B), together with hypermetabolic ipsilateral hilar lymph nodes (C and D). The patient underwent surgery, which further confirmed the diagnosis of tuberculosis.

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Table 1
Summary of recommendations for the management of patients with indeterminate solitary pulmonary nodules.

Figure 1 A: Axial fused ¹⁸F-FDG PET/CT image. B: Axial PET image. Patient with history of epidermoid cervical carcinoma, referred for indeterminate pulmonary nodule research. Upon ¹⁸F-FDG PET/CT examination, the nodule displayed increased glycolytic metabolism (SUVmax = 5.6). She was submitted to surgery, which confirmed the hypothesis of involvement of the underlying disease.

Figure 2 A: Axial fused ¹⁸F-FDG PET/CT image. ^B: Axial PET image. Patient with no history of cancer referred for investigation of an indeterminate pulmonary nodule. Upon ¹⁸F-FDG PET/CT examination, the pulmonary nodule showed no anomalous accumulation of the tracer.

Figure 3 A: Axial fused ¹⁸F-FDG PET/CT image. B: Axial chest CT image. C: Axial fused ¹⁸F-FDG PET/CT image. D: PET axial image. Patient with a history of gastrointestinal stromal tumor presenting with indeterminate pulmonary nodule in the right lower lobe in a previous CT scan. Upon ¹⁸F-FDG PET/CT examination, the nodule displayed slightly increased glycolytic metabolism when compared with normal lung parenchyma (arrows in A and B), together with hypermetabolic ipsilateral hilar lymph nodes (C and D). The patient underwent surgery, which further confirmed the diagnosis of tuberculosis.

Table 1 Summary of recommendations for the management of patients with indeterminate solitary pulmonary nodules.

Patient with a solid indeterminate solitary pulmonary nodule with a diameter > 0.8 cm

• A functional image, preferably PET, is suggested for nodule characterization, in an individual with low to moderate pre-test probability (5% to 65%).
• PET can be indicated with the aim of pre-treatment staging and not for characterizing the nodule in a patient with high pre-test probability (> 65%).
• Follow-up with CT (3 to 6 months, 9 to 12 months and 18 to 24 months, using low dose technique without contrast ) is suggested in the following circumstances: – when the clinical probability of malignancy is very low (< 5%);
- when the clinical probability is low (< 30% to 40%) and the results of the functional image tests are negative, resulting in a very low post-test probability of malignancy;
– when the biopsy is inconclusive and the injury is not hypermetabolic on PET;
– when the patient prefers a nonsurgical approach.
• Biopsy and/or surgical resection is suggested in individuals with evidence of malignant growth in serial images (unless there are specific contraindications).
• Biopsy is suggested in the following circumstances: – when the pre-test clinical probability and imaging findings are discordant;
– when the probability of malignancy is low to moderate (10% a 60%);
– when there is suspicion of a benign lesion that requires specific medical treatment;
– when the patient desires proof of a malignant diagnosis prior to surgery, especially if the risk of surgical complications is high .
• Surgery is suggested in the following circumstances: – when the clinical probability of malignancy is high (> 65%);
– when the nodule is intensely hypermetabolic on PET or positive on another functional image test;
– when the biopsy is suggestive of malignancy;
– when the patient prefers to undergo a definitive diagnostic procedure.

Patient with a solid indeterminate solitary pulmonary nodule with a diameter ≤ 0.8 cm and no risk factors for lung cancer

• Nodules ≤ 0.4 cm do not need to be monitored, but the patient must be informed of the potential risks and benefits.
• Nodules measuring > 0.4 cm and ≤ 0.6 cm should be reevaluated after 12 months without the need for follow-up if they remain unchanged.
• Nodules > 0.6 cm and ≤ 0.8 cm should be reevaluated after 6 to 12 months and again after 18 to 24 months if they remain unchanged.

Patient with a solid indeterminate solitary pulmonary nodule with a diameter ≤ 0.8 cm and one or more risk factors for lung cancer

• Nodules ≤ 0.4 cm should be reevaluated after 12 months, without the need for follow-up if they remain unchanged.
• Nodules measuring > 0.4 cm and ≤ 0.6 cm should be reevaluated after 6 to 12 months and again after 18 to 24 months if they remain unchanged.
• Nodules > 0.6 cm and ≤ 0.8 cm should be reevaluated after 3 to 6 months, after 9 to 12 months and again after 24 months if they remain unchanged.

Patient with a non-solid (ground-glass) indeterminate pulmonary nodule

• For nodules ≤ 0.5 cm, monitoring is not mandatory.
• Nodules > 0.5 cm should be monitored annually for at least three years.

Patient with a part-solid (> 50% ground-glass) indeterminate pulmonary nodule

• For nodules ≤ 0.8 cm, it is suggested that the patient be reevaluated after approximately 3, 12, and 24 months, and that annual CT scans be obtained for an additional 1 to 3 years.
• For nodules > 0.8 cm, it is suggested that the chest CT scan be repeated after 3 months, and that that be followed by evaluation by PET, biopsy, or surgical resection for any remaining nodules.
• Nodules > 1.5 cm should immediately be submitted to evaluation by PET, biopsy, or surgical resection.

Adapted from American College of Chest Physicians⁽³⁴34 Gould MK, Donington J, Lynch WR, et al. Evaluation of patients with pulmonary nodules: when is it lung cancer? Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2013;143(5 Suppl):e93S-120S.⁾.

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