CASE DESCRIPTION
A 5-month-old girl presented with suspected bronchiolitis, vomiting,
adenovirus positive bloody diarrhoea and an abdominal mass. An
ultrasound scan confirmed a left heterogeneous suprarenal mass (70 x 40
mm) with internal calcification crossing the midline with recognised
imaging characteristics of NB of vascular encasement of both the aorta
and superior mesenteric artery.
Urinary catecholamines were elevated; 4-hydroxy-3-methoxymandelic acid
(HMMA) to creatinine ratio of 31.8 (0-12) and
4-hydroxy-3-methoxyphenylacetic acid (HVA) to creatinine ratio of 35.9
(3-15). Magnetic resonance imaging (MRI) demonstrated a peripherally
enhancing bosselated multinodular mass (62 x 70 x 79 mm; 178 ml)
displacing the left kidney and encasing the left renal pedicle(Fig. 1A ). Tumour volume was calculated using the formula,
volume = (π/6) × antero-posterior (depth) × width × cranio-caudal
measurements.13 Completion staging with computed
tomography (CT) showed no intracranial or pulmonary metastatic
dissemination with a metaiodobenzylguanidine (MIBG) scan showing
localised uptake at the primary site with no focal bony uptake/
dissemination. An ultrasound guided biopsy confirmed favourable
histology using the International Neuroblastoma Pathology Classification
(INPC), without MYCN amplification, with triploidy and no
segmental chromosomal abnormalities (SCAs) (favourable biology)
(Fig. 2A-D ).
A diagnosis of low-risk, localised, unresectable, stage L2 neuroblastoma
was made as per the International Neuroblastoma Risk Group Staging
System (INRGSS).14 For patients aged < 18
months at diagnosis with L2 neuroblastoma, no SCAs and no life or organ
threatening features, a close surveillance strategy using 3 monthly
interval MRI scans and urinary catecholamine monitoring is
indicated.15
Surveillance MRI performed at 3 months, demonstrated interval increase
in tumour size and volume (71 x 100 x 97 mm; 358 ml) including a central
area of necrosis. However, the child remained asymptomatic, so ongoing 3
monthly MRI surveillance was planned\sout.
Five months after diagnosis, there was a > 9-fold increase
in urinary catecholamines. Active treatment with chemotherapy was
considered because of substantial tumour growth and increasing tumour
markers (Fig. 1D-E). However, symptoms remained mild and after
discussion with the family, close observation was continued.
A third MRI, 6 months after diagnosis, showed ongoing tumour growth (77
x 110 x 130 mm: 572ml, with a 50 x 50 mm central area of tumoural
necrosis) and displacement of the left kidney but no hydronephrosis.
Urine catecholamines had increased further to > 10-13 x the
diagnosis levels. Despite worsening radiological and biomarker trends,
the child was now completely asymptomatic.
Nine months after diagnosis, MRI scanning showed further interval tumour
growth but for the first time, a reduction of urinary catecholamines
(Fig. 1D ). An MRI scan 12 months after diagnosis for the first
time showed measurable reduction in tumour size in all 3 planes and with
urinary catecholamine levels continuing to fall.
Subsequent serial MRI scans at 16, 21, 27, 33 and 43 months showed
continued tumour regression followed by stabilisation. Urinary
catecholamines returned to the normal range 28 months after diagnosis
and have remained normal since then (Fig. 1D-1E).