Definition:

Increase in diameter of a mass compared to its baseline by a minimum of 5 mm AND depending on the time interval between examinations, by the following amounts:

• <6 months: >50% diameter increase 
• >6 months: >100% diameter increase

Usage

• Applies to masses; it does not apply to observations that are not masses (e.g., perfusion alterations, hepatic fat deposition).
• Major feature for categorization of masses that are neither definite benign entities nor probable benign entities and that lack features of non-HCC malignancy or tumor in vein.
• Growth should be assessed on images acquired in the same plane and, if possible, the same phase or sequence.
• If margins are sharply demarcated on more than one sequence or phase, do not measure in the arterial phase.
• Cross modality comparison (CT vs MR) should be used with caution to assess growth.
• A new > 10 mm mass also represents threshold growth, regardless of the time interval.
• A new < 10 mm mass does not represent threshold growth.

Background

• Interval growth is predictive of HCC and follow-up imaging is used to assess the rate of growth. HCC demonstrate a large range of growth rates, with tumor volume doubling times ranging from less than 20 days to over one year. Examining HCC initially presenting as a smaller than 2 cm lesion, Furlan et al found a tumor volume doubling time of 210 days, suggesting an optimal follow-up of six months. Initially hypovascular nodules with a high growth rate also had a higher incidence of hypervascularization on subsequent follow-up (Hyodo et al)

• UNOS/OPTN recognizes growth only as ≥ 50% increase in diameter in ≤ 6 months.  In addition, the observation must have been seen on a previous exam to demonstrate growth.  A new observation does not demonstrate growth according to UNOS/OPTN policy.

Potential pitfalls and challenges

• As shown in Table, masses with threshold growth, but without arterial phase hyperenhancement cannot be categorized LR-5.

References:

Jeong YY et al, Small (<20 mm) enhancing hepatic nodules seen on arterial phase MR imaging of the cirrhotic liver: clinical implications. AJR Am J Roentgeno 2002; 178(6);1327-34.

Taouli B et al, Growth rate of hepatocellular carcinoma: evaluation with serial computed tomography or magnetic resonance imaging. J Comput Assist Tomogr 2005; 29(4): 425-9

Cucchetti A et al, Tumor doubling time predicts recurrence after surgery and describes the histological pattern of HCC on cirrhosis. J of Hepatology 2005; 43(2):310-6

Hwang SH et al, Small hypervascular enhancing lesions on arterial phase images of multiphase dynamic computed tomography in cirrhotic liver: fate and implications. J Comput Assist Tomogr 2008;32(1):39-45

Khalili K et al, Indeterminate 1-2 cm nodules found on hepatocellular carcinoma surveillance: biopsy for all, some, or none? Hepatology 2011; 54(6): 2048-54

Furlan A et al, Hepatocellular carcinoma presenting at contrast-enhanced multi-detector-row computed tomography or gadolinium-enhanced magnetic resonance imaging as a small (≤2 cm), indeterminate nodule: growth rate and optimal interval time for imaging follow-up. J Comput Assist Tomogr 2012; 36(1): 20-5

Hyodo T et al, Hypovascular nodules in patients with chronic liver disease: risk factors for development of hypervascular hepatocellular carcinoma. Radiology 2013; 266(2): l480-90