Comparative Role of ¹⁸F-DOPA PET/CT and ¹³¹I-MIBG Scintigraphy in Neuroblastoma and Application of Curie and SIOPEN Scoring Systems in ¹⁸F-DOPA PET/CT

Abstract

Purpose

Neuroblastoma (NB) is childhood’s most common extracranial solid malignancy. We have compared two imaging modalities, ¹³¹I-MIBG and ¹⁸F-DOPA PET/CT, to evaluate NB. Also, feasibility of the application of standardised scoring systems, SIOPEN and Curie scoring systems, in ¹⁸F-DOPA PET/CT was explored.

Methods

Patients with histopathology-proven NB underwent ¹³¹I-MIBG (planar and SPECT/CT) and ¹⁸F-DOPA PET/CT scans, as per standard imaging protocols. Duration between scans ranged from 1 to 30 days (median = 8 days). Number of lesions in Curie and SIOPEN scoring systems applied on both modalities was compared.

Results

Forty-six patients were included (M:F = 29:17) with a median age of 36 months. Both ¹³¹I-MIBG and ¹⁸F-DOPA scans were positive in 39 patients and negative in four patients. ¹⁸F-DOPA PET/CT was positive in additional three patients, in which ¹³¹I-MIBG was negative (p = 0.25). Overall, ¹⁸F-DOPA identified significantly greater number of lesions than ¹³¹I-MIBG, especially metastatic skeletal lesions (p < 0.05). Significant difference was observed between Curie scores in the two modalities, unlike SIOPEN scores. However, when the cut-off age of 18 months was taken, no significant difference was seen in either of the scoring systems in both the scans (p > 0.05). CS and SIOPEN scores were significantly higher in bone marrow-positive patients.

Conclusion

¹⁸F-DOPA PET/CT detected more lesions than ¹³¹I-MIBG but had little impact on staging of the disease. For evaluation of NB, both scans can be used interchangeably as per the availability. Furthermore, both SIOPEN and Curie scoring systems, standardised for MIBG, can also be used to semi-quantify disease extent in ¹⁸F-DOPA PET/CT.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13139-022-00762-6.

Introduction

Neuroblastoma (NB) is an extracranial solid tumour that is among most common paediatric cancers. It arises mostly from the adrenal gland, retroperitoneum, posterior mediastinum, and pelvic and cervical region. Twenty-two months is the median age at diagnosis with more than 80% of cases being diagnosed by the age of 4 years. Majority of the cases are metastatic at presentation, with bone/bone marrow being the most common site of metastasis [1–5].

Multiple imaging modalities are used to evaluate the disease. Ultrasonography (USG) is useful for primary tumour evaluation and is often the initial investigation. Computed tomography (CT) and magnetic resonance imaging (MRI) are done to evaluate distant metastasis. MRI is particularly helpful in detecting intraspinal extension of the tumour and encasement of vascular bundles, thus helping decide eligibility for surgery. MRI is more sensitive than ¹²³I-MIBG in detecting bone marrow lesions. However, it cannot distinguish between active and treated diseases [6–9]. ¹²³I-metaiodobenzylguandine (MIBG) scan is recommended as the first-line functional imaging agent for NB since it enables visualisation of the primary and metastatic lesions. It allows functional assessment to help differentiate active tumours from post-therapy changes [10, 11]. However, ¹²³I-MIBG has limited availability, and its commonly used substitute, ¹³¹I-MIBG, has lower sensitivity because of dose constraints.

Various semiquantitative scoring systems are used to evaluate disease extent. Two MIBG scoring systems that have gained popularity and can be used as a prognostic indicator are International Society of Pediatric Oncology Europe Neuroblastoma (SIOPEN) and Curie scoring (CS) systems [1, 12, 13].

^99mTc-methylene diphosphonate (MDP) bone scan and/or ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scan are recommended for evaluation of ¹²³I-MIBG-negative patients [14–16]. Other nuclear medicine modalities that can be used are ⁶⁸ Ga-labelled somatostatin receptors imaging agents, like ⁶⁸ Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic-acid-1-Nal3-octreotide (DOTANOC), ⁶⁸ Ga-DOTA-Phe¹-Tyr³-octreotide (DOTATOC), or ⁶⁸ Ga-DOTA-octreotate (DOTATATE). ¹⁸F-fluoro-dihydroxyphenylalanine (DOPA) PET/CT has shown promising results. Accelerated metabolism of catecholamines is a characteristic of NB. DOPA is a precursor of both dopamine as well as catecholamines. L-type amino acid transporter (LAT1) actively transports it into cells where the enzyme aromatic amino acid decarboxylase (AADC) converts it into dopamine [17]. Owing to its ability to follow the metabolism of catecholamines, ¹⁸F-DOPA is the most promising PET alternative to ¹²³I-MIBG in neural crest tumours [14, 18–20].

The present study aims to evaluate the role of ¹⁸F-DOPA PET/CT in NB and compare it with the ¹³¹I-MIBG scan. Semiquantitative evaluation of these patients using Curie score and SIOPEN scoring system in MIBG was done, and the feasibility of application of these scoring systems in ¹⁸F-DOPA PET/CT was also explored.

Materials and Methods

It was a prospective observational study. Patients with biopsy-proven NB referred for staging or restaging were included in the study, irrespective of age and gender.

Informed consent: written informed consent was taken from all patients/legally authorised representatives.

Ethical approval: ethical clearance for the study was obtained from Institute Ethics Committee (IECPG-329/18.07.2018, RT-14/30.08.2018)

All patients underwent ¹³¹I-MIBG scintigraphy and ¹⁸F-DOPA PET/CT as per the following protocol. The time interval between two modalities was within 1 month.

¹³¹I-MIBG Scintigraphy Procedure

Patients were injected 37 ± 12 MBq (1 ± 0.32 mCi) of ¹³¹I-MIBG (procured from BARC, Mumbai, India) intravenously. Lugol’s solution was given orally to the patients, starting from a day before administration of ¹³¹I-MIBG and continued for the next 5 days to protect the thyroid from any unnecessary radiation dose. Images were acquired on a large field of view dual-head single photon emission computed tomography (SPECT/CT) scanner (Discovery NM/CT 670, General Electric Company, USA). Whole-body planar images were acquired first, using high energy collimator 48–72 h post-injection, followed by SPECT/CT of the region of interest was acquired (parameters: matrix size = 128 × 128, 120 projections with 3° increments, 40 s per projection). Images were reconstructed using filtered back projection with no prefiltering, reconstruction with a ramp filter, and post-processing with low-pass filter.

¹⁸F-DOPA PET/CT Procedure

A dose of 5 MBq/kg (0.135 mCi/kg) ¹⁸F-DOPA was injected intravenously. Whole-body PET/CT (vertex to toe) was acquired 45–60 min post-injection on dedicated PET/CT scanners (Discovery 710, General Electric Company, USA and Biograph mCT, Siemens Healthcare, Henkestr, Erlangen, Germany). An initial scout (20 mA and 80 kV) of the whole-body region was obtained with the patient positioned supine on the scan table. Low-dose CT acquisition for attenuation correction was made, followed by a three-dimensional (3D) whole-body PET study performed for 2 min/bed position. Data were reconstructed using the iterative reconstruction technique. Images were viewed for interpretation on the ADW version 4.3 system.

Analysis

All scans were evaluated independently by two experienced nuclear medicine physicians for the area of abnormally increased radiotracer uptake. Uptake more than liver (background) was considered as abnormal. For per-patient analysis, scans were considered positive when at least one focus of abnormally increased uptake lesion (primary or metastatic) was seen, regardless of the number of foci. For comparison between SPECT/CT and PET/CT, PET/CT was analysed by limiting the region of analysis to the scope of SPECT/CT. The score was given to each scan according to Curie and SIOPEN scoring systems (guide to both the scoring systems is provided as “Supplement 1”).

Statistical Analysis

Various descriptive statistics such as median, range, and interquartile (IQR) were used to summarise all the subjects’ baseline clinical and demographic profiles. The normality of the distribution was checked by Shapiro–Wilk test for normality. Diagnostic performance of ¹⁸F-DOPA PET/CT and ¹³¹I-MIBG scan was compared by McNemar test. Wilcoxon and Mann–Whitney U test was used to compare two paired groups and to compare the difference between two independent groups, respectively. Analysis was done with the MedCalc Software Bvba, Ostend, Belgium (2018, version 18.2.1). p value < 0.05 was considered statistically significant.

Results

Forty-six patients (29 male; 17 female) were included in the final analysis. Data was not normally distributed as the p values were found to be significant (< 0.05). Patient characteristics are given in Table 1. Forty-two patients were referred for staging and the other four patients for restaging. The most common site for the primary was abdomen (n = 32), followed by thorax (n = 10). Head and neck primary was seen in two cases, pelvis in one case, and only metastasis with no observable primary was seen in one case.

Table 1.

Patient characteristics

Characteristics		Value
Total number of patients		46
Gender (male:female)		29:17
Age median (IQR) (months)		36 (12–51)
Indication for scan	Baseline evaluation	42
	Restaging	4
Site of primary	Abdomen	32 (69.5%)
	Thorax	10 (21.7%)
	Head and neck	2 (4.3%)
	Pelvis	1 (2.1%)
	Only metastatic	1 (2.1%)
MYCN gene amplification (n = 9)	Positive	2
	Negative	7
Urinary catecholamine levels (n = 23)	Elevated	20
	Normal	3
Bone marrow biopsy (n = 35)	Positive	14
	Negative	18
	Inadequate sample	3

Patient-Wise Analysis

Both ¹³¹I-MIBG scan and ¹⁸F-DOPA PET/CT were positive in thirty-nine studies, and both were negative in four studies. In three studies, discrepancy was seen, in which ¹⁸F-DOPA PET/CT was positive, and ¹³¹I-MIBG scan was negative (Table 2).

Table 2.

Patient-wise and lesion-wise analyses

Patient-wise analysis
	18F-DOPA negative	18F-DOPA positive	Total
131I-MIBG negative	4	3	7 (15.2%)
131I-MIBG positive	0	39	39 (84.8%)
	4 (8.7%)	42 (91.3%)	46
Lesion-wise analysis
	Skeletal lesions	Soft tissue lesions	Total
18F-DOPA MIP	273	67	340
131I-MIBG planar	195	44	239
18F-DOPA PET/CT	267	96	363
131I-MIBG SPECT/CT	157	72	229

There was no significant difference in paired proportions of positive and negative scans between ¹³¹I-MIBG and ¹⁸F-DOPA PET/CT (p = 0.25). Figure 1 shows 2-year-old boy with thoracic NB, which showed ¹⁸F-DOPA uptake in the primary tumour while no ¹³¹I-MIBG accumulation.

Fig. 1.

Baseline staging scan of 2-year-old male patient with thoracic NB. a ¹³¹I-MIBG planar showed no abnormal radiotracer uptake; b ¹⁸F-DOPA MIP showed tracer uptake in the primary tumour (white arrow); corresponding c axial CT and d SPECT/CT are not showing tracer accumulation in the right paraspinal tumour in the thorax; e PET/CT showed.¹⁸F-DOPA uptake

Lesion-Wise Analysis

¹⁸F-DOPA MIP vs.¹³¹I-MIBG Planar

The total number of lesions detected in both modalities is described in Table 2. Greater number of lesions were detected in maximum intensity projection (MIP) of ¹⁸F-DOPA scan as compared to that in planar ¹³¹I-MIBG. The difference between the two was statistically significant (p = 0.0091). On average, ¹⁸F-DOPA MIP identified more skeletal lesions than planar ¹³¹I-MIBG (p = 0.0398). The difference between the two modalities in detecting soft tissue lesions was not significant (p = 0.17).

¹⁸F-DOPA PET/CT vs.¹³¹I-MIBG SPECT/CT

Due to technical issues, SPECT/CT was available only in 43 out of 46 patients. Therefore, analysis was done in 43 patients only. Difference between the two modalities in detecting the number of total lesions was significant (p = 0.0012). ¹⁸F-DOPA PET/CT identified a greater number of skeletal lesions and total lesions than ¹³¹I-MIBG SPECT/CT (p = 0.0034) (Table 2 and Fig. 2). There was no significant difference in the number of soft tissue lesions detected by the two modalities (p = 0.12). Intraspinal extension were better visualised in ¹⁸F-DOPA PET/CT scan (Fig. 3).

Fig. 2.

Baseline staging scan of 4-month-old female patient with thoracic NB, a ¹³¹I-MIBG planar, and b ¹⁸F-DOPA MIP showed increased tracer uptake in the primary tumour in the thorax and metastatic lesions in the liver. However, ¹⁸F-DOPA images showed extensive metastatic lesions in muscle and bone/bone marrow which was not evident in.¹³¹I-MIBG, c coronal CT and d SPECT/CT; e fused PET/CT showed multiple tracer avid hypodense liver lesions and muscles metastatic lesions

Fig. 3.

Baseline staging scan of 2-year-old male patient with retroperitoneal NB, a ¹³¹I-MIBG planar, and b.¹⁸F-DOPA MIP showed increased tracer uptake in the right abdomen region. c Axial CT and d axial SPECT/CT showed tracer accumulation in the primary, and e axial PET/CT showed tracer accumulation in the primary as well as intra-spinal extension. This lesion was more evident in f sagittal SPECT/CT, which did not show any tracer uptake, whereas g sagittal PET/CT showed tracer uptake in the intraspinal region

Scoring Analysis

Curie and SIOPEN Scores in ¹³¹I-MIBG and.¹⁸F-DOPA Scan

Curie and SIOPEN scores in ¹⁸F-DOPA PET/CT and ¹³¹I-MIBG planar are shown in detail in Table 3. Overall median Curie score in MIBG and DOPA scan was 2 and 3, respectively. Difference between the Curie scores of both scans was found to be statistically significant (p = 0.0235). However, the difference between the SIOPEN scores of both scans was not significant (p = 0.19), the overall median SIOPEN score being 0 in both MIBG as well as DOPA scan.

Table 3.

Curie and SIOPEN scores of all patients in the study, categorised in bone marrow positive and negative patients, and categorised in patients ≤ 18 and > 18 months of age

	All patients median (IQR)	BM positive (median)	BM negative (median)	p value	Age ≤ 18 months (median)	Age > 18 months (median)	p value
CS
131I-MIBG	2 (1–8)	12 (4–24)	1.5 (1–3)	0.008	3 (0.5–5)	2 (1–13)	0.650
18F-DOPA	3 (1–16)	18.5 (5–24)	2.5 (1–3)	0.004	3 (1–4)	3 (1–21)	0.324
SIOPEN score
131I-MIBG	0 (0–7)	18.5 (1–37)	0 (0–0)	0.001	0 (0–3)	0 (0–21)	0.294
18F-DOPA	0 (0–15)	20 (4–46)	0 (0–0)	0.000	0 (0–1)	0 (0–28)	0.109

BM, bone marrow; CS, Curie score

Distribution of scores based on age as risk factor—out of 46 patients, 12 patients (26%) were below or equal to 18 months, and 34 (74%) patients were above 18 months. There was no significant difference in scores between the two age groups (Table 3). In MIBG scan, median Curie score in age group of ≤ 18 months and > 18 months was 3 and 2, respectively (p = 0.65) and in DOPA scan, the same was 3 for both age groups (p = 0.32). Median SIOPEN score was 0 for both the scans for both the age groups (p > 0.05).

Distribution of scores based on findings of bone marrow biopsy—out of 46 patients, bone marrow biopsy was performed in 35 patients; of which, 14 were positive for malignant cells, 18 were negative, and in three cases, bone marrow samples were inadequate for opinion and were not analysed. Scores between both groups were compared for both scans. On both the modalities, there was a significant difference between BM positive and negative groups in Curie as well as SIOPEN scoring systems (Table 3). In MIBG scan, median CS in BM positive and negative group was 12 and 1.5 (p = 0.008) and that in DOPA scan was 18.5 and 2.5 (p = 0.004), respectively. Median SIOPEN score in MIBG scan in BM positive and negative group was 18.5 and 0 (p = 0.001) and that in DOPA scan was 20 and 0 (0.0003). Bone marrow biopsy positive patients have significantly higher CS and SIOPEN indicating greater extent of the disease, with a minimum ratio of 3.9, that is, on average, at least 3.9 times increase in extent can be expected in BM positive patients compared to when bone marrow biopsy is negative (details provided as “Supplementary 2”).

Discussion

Staging and metastatic evaluation of NB tumours are done before starting treatment, using multiple modalities, including radiology and nuclear medicine scans. ¹²³I-MIBG is mandatory for staging according to International Neuroblastoma Risk Group Staging System (INRGSS) and is the preferred imaging modality for staging and response assessment in NB. Earlier, ¹³¹I-MIBG was used for imaging of NB, as ¹²³I-MIBG was not Food and Drug Administration (FDA) approved. But now ¹²³I-MIBG is preferred due to its better imaging quality and lesser radiation dose to the patient. However, due to its unavailability in India, ¹³¹I-MIBG is used as an alternative for imaging of NB [21].

Patient-Wise Analysis

In our study, out of 46 paired scans, ¹⁸F-DOPA PET/CT was found positive in 42 patients (91.3%) while ¹³¹I-MIBG scan was positive in 39 patients (84.8%). In three studies, ¹⁸F-DOPA PET/CT scan showed uptake in the primary lesion, whereas there was no ¹³¹I-MIBG accumulation. In a study done by Piccardo et al. in 19 patients with stage 3 and 4 NB, the disease was confirmed in 16 patients (94%) by ¹⁸F-DOPA PET/CT scan and in 11 patients (65%) by ¹²³I-MIBG scan [22]. In our study, although ¹⁸F-DOPA PET/CT detected more patients with the disease, however, statistically, there was no significant difference between the two modalities.

Lesion-Wise Analysis

Comparison of Planar vs MIP

The total number of lesions and skeletal lesions detected on MIP of ¹⁸F-DOPA scan was significantly greater, likely due to its higher resolution than the planar ¹³¹I-MIBG scintigraphy. Similar findings were also demonstrated by Piccardo et al.. In their study, 156 NB lesions were identified in 28 paired ¹²³I-MIBG and ¹⁸F-DOPA scans, of which ¹⁸F-DOPA detected 141 and ¹²³I-MIBG detected 88 lesions [22]. Like previous studies, in our study too, we observed that the number of total lesions and skeletal lesions detected on ¹⁸F-DOPA MIP was more than that on the ¹³¹I-MIBG planar images. However, there was no significant difference in detecting soft tissue lesions.

SPECT/CT vs PET/CT

The total number of lesions and skeletal lesions detected on the ¹⁸F-DOPA PET/CT scan was significantly higher than the ¹³¹I-MIBG SPECT/CT scan (Table 2). This can be explained by the fact that PET/CT has a higher resolution than SPECT/CT. Further, SPECT/CT is known to have an incremental benefit over planar images. Studies done by Rozovsky et al., Fukuoka et al., and Liu et al. demonstrated that SPECT/CT gave additional information, anatomical localisation over planar, and also increased confidence over image interpretation [23–25]. However, in our study, whole-body (vertex to toe) planar detected more lesions than SPECT/CT, since only a limited region SPECT/CT was performed.

Scoring Analysis

A scoring system in MIBG scan helps in semi-quantifying the extent of uptake in individual patients, in addition to serving as an imaging biomarker for predicting the outcome of the disease. Currently, Curie and SIOPEN scoring systems are used for MIBG. Scan type, i.e. ¹²³I-MIBG or ¹³¹I-MIBG, has no effect on outcome prediction at diagnosis or post-induction [26].

For PET scans, semiquantitative analysis using standardised uptake values (SUVs) is well established. However, in MIBG intensity of uptake is difficult to measure visually. Semiquantification, therefore, is done using the extent of MIBG uptake. For ¹⁸F-DOPA PET/CT, no such scoring system, based on just the extent of disease, has been previously reported. Piccardo et al. used a scoring system for both ¹²³I-MIBG scan and ¹⁸F-DOPA PET/CT for evaluation of NB. For ¹²³I-MIBG, they used the SIOPEN method three scoring system, and for ¹⁸F-DOPA, they used whole-body metabolic burden (WBMB). WBMB was calculated using SUVmean and the SIOPEN and Curie scores. They found good agreement between the ¹⁸F-DOPA WBMB score and the ¹²³I-MIBG score, and post-therapeutic ¹⁸F-DOPA WBMB was the only risk factor associated with disease progression, in a time-to-event analysis [18].

In this study, only the extent of disease was taken for scoring the ¹⁸F-DOPA PET/CT. The same method was applied on both the ¹⁸F-DOPA PET/CT and ¹³¹I-MIBG scan. The intensity of uptake was not included. In our study, there was a significant difference between CS but no difference between SIOPEN scores of both the scans. Curie and SIOPEN scoring systems have not been validated for ¹⁸F-DOPA PET/CT scans in any of the previous studies and hence there is no parallel in literature to draw a comparison. However, probable reason for the observed difference can be that Curie scoring system takes into account both soft tissue as well as skeletal disease burden while SIOPEN system is based entirely on skeletal burden. Further, MIBG planar scan involves whole body 2D acquisition and SPECT is acquired only over a particular region of interest, unlike DOPA PET scan that involves whole body 3D volume acquisition. Inclusion of soft tissue in Curie score and lower resolution of MIBG scan may cause subtle soft tissue lesions to be missed on MIBG thereby affecting its Curie scores.

Earlier, diagnosis at the age of > 12 months was considered as the indicator of unfavourable outcome, which was later increased to > 18 months [27]. Riaz et al. showed a positive correlation between poor prognostic indicators and MIBG CS and SIOPEN scores in stage 4 NB. They reported significantly higher CS and SIOPEN scores of patients who were diagnosed at the age of > 18 months [28]. In our study, we considered the cut-off of 18 months as a risk factor and found no significant difference between the two groups in either of the scoring systems for both scans. Unlike previous studies, we could not find any positive correlation between the age > 18 months and CS and SIOPEN scores (Table 3). This might be due to heterogeneity in our sample with respect to disease stage.

In infants, presence of bone/bone marrow metastasis in NB is classified as intermediate risk, whereas in children > 12 months of age, it is classified as high risk [29]. CS shows disease extent in both soft tissues as well as bone/bone marrow, whereas the SIOPEN scoring system exclusively shows skeletal metastasis burden. Accordingly, in our study also, we observed that BM positive patients had extensive bone marrow involvement and greater disease extent, thus having significantly higher CS and SIOPEN scores on both MIBG as well as DOPA scans (Table 3).

There are certain limitations to both the modalities used in the present study. Firstly, intense physiological uptake of ¹⁸F-DOPA in the gall bladder, biliary tract, and pancreas makes the interpretation of primary lesion and liver metastasis difficult. Also, the cost is relatively high, making it less affordable. On the other hand, the ¹³¹I-MIBG scan has low resolution, and hence smaller lesions may be missed if not reported carefully. SPECT/CT is done to overcome the problem and characterise the lesion. However, as mentioned earlier, it is usually a regional scan. Image-defined risk factors (IDRFs) such as intraspinal extension are better visualised and appreciated on ¹⁸F-DOPA scan (Fig. 3). The ¹³¹I-MIBG scan is time-consuming and takes 48 to 72 h from injection to the scan and requires thyroid blockage with Lugol’s iodine. In contrast, the ¹⁸F-DOPA scan is a single-day process and requires no pre-scan preparation. So far as the present study is concerned, although the results are encouraging, a larger, more homogenous sample could further validate the results, and a long-term follow-up is required to correlate scoring with prognosis.

Conclusion

In our study, we concluded that both the ¹⁸F-DOPA and ¹³¹I-MIBG scan can be done interchangeably for the evaluation of NB. Even though the total number of lesions detected, especially skeletal lesions, by ¹⁸F-DOPA PET/CT was higher than the ¹³¹I-MIBG scan, it did not change the overall staging of the patient. Being a theragnostic agent, ¹³¹I-MIBG has an added advantage over ¹⁸F-DOPA PET/CT. While the SIOPEN score can be applied in ¹⁸F-DOPA PET/CT to evaluate disease burden, as it mainly considers skeletal involvement, application of the Curie score in the ¹⁸F-DOPA scan needs to be further studied in detail. Furthermore, long-term follow-up is required to correlate the scoring with prognosis.

Supplementary Information

Below is the link to the electronic supplementary material.

Author Contribution

The study was designed by Chandrasekhar Bal and Nishikant Avinash Damle. Material preparation and data collection were performed by Angel Hemrom and Geetanjali Arora. The data analysis was performed by Angel Hemrom and Chandrasekhar Bal. The first draft of the manuscript was written by Angel Hemrom and Geetanjali Arora and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data Availability

Data may be available from the corresponding author upon reasonable data requests.

Declarations

Conflict of Interest

Angel Hemrom, Geetanjali Arora, Nishikant Avinash Damle, and Chandrasekhar Bal declare no conflict of interest.

Ethics Approval and Consent to Participate

The study was approved by the institutional ethics committee of All India Institute of Medical Sciences, New Delhi, India (IECPG329/18.07.2018, RT-14/30.08.2018), and informed consent was obtained from all individual participants included in the study. All procedures performed in studies involving human participants were in accordance with the Helsinki declaration as revised in 2013 and its later amendments.

Consent for Publication

Not applicable.