Time Trends of Incidence and Relative Frequency of Participants in Clinical Trials
The population-based median annual age standardized incidence rate (ASR) of neuroblastoma per million children per year in Germany between the periods 1980 and 2015 was 13.2 (minimum 8.7 , incomplete registration; maximum 17.8 , last year of screening trial). For stages 1–3, the median ASR was 6.3 (minimum 3.3 ; maximum 9.5 ), and for stage 4, it was 4.6 (minimum 2.6 ; maximum 6.6 ).
The age-adjusted regression curve (Fig. 1) shows an increase in crude neuroblastoma incidence rates during the period of neuroblastoma screening (RR 1.26; 95% CI 1.17–1.36), with a 7% increase per 10 years for neuroblastoma (RR/10 years 1.07; 95% CI 1.03–1.12; data adjusted for the screening period). Much of the increase resulted mainly from stage 1–3 diagnoses (RR during screening 1.40; 2010 vs. 2000 RR 1.10; 95% CI 1.04–1.15). This was particularly evident for the group aged 1 to <2 years for stage 1–3 tumors, which showed a screening-adjusted increase of 20% from 2000 to 2010 (RR 2010 vs. 2000 1.20; 95% CI 1.03–1.40). The incidence of neuroblastoma stage 4S (<1 year of age) increased by 14% (RR 2010 vs. 2000 1.14; 95% CI 1.07–1.21), with a flattening curve in recent years. No significant change was observed over time for the total group of children with stage 4 neuroblastoma, neither during the screening period nor afterwards (RR 2010 vs. 2000 0.98, 95% CI 0.91–1.06). Among stage 4 patients, patients aged <1 year showed a small increase of 3% over a 10-year period (RR 1.03; 95% CI 0.93–1.14) and for the children aged 1 to <2 years, a 12% decrease in neuroblastoma incidence per 10-year period (RR 0.88; 95% CI 0.75–1.03) was observed. Overall, no change in incidence of stage 4 patients was seen, whereas an increase in localized stages and stage 4S was observed.
The percentage of patients who were resident in Germany, known to the nationwide German Childhood Cancer Registry during the periods 1980–2015 and participated in the neuroblastoma trials was 96.6%. The coverage was less during the early 1980s, reached more than 90% during the period 1985–1994, and was consistently ≥98% from 1995 to 2015.
Frequencies of Stages, Age at Diagnosis, and Time to Diagnosis
A total of 4463 patients were enrolled into one of the nationwide trials between 1979 and 2015. Table 1 shows the number of patients in the trials and the relative stage distribution. Half of the cohort (51%) had localized/regional neuroblastoma stages (1–3), roughly 11% stage 4S, and 38% stage 4 disease. The proportion of stage 1–3 increased during the neuroblastoma screening period .
Patients with neuroblastoma were diagnosed at an earlier age in more recent years (Table 2). The median age at diagnosis decreased from 23 months during 1980–1984 to 15 months during 2010–2014. The drop occurred continuously but was particularly evident during and following the neuroblastoma screening period (NB97 and NB2004). The median age at diagnosis is now 10 months for stages 1–3 and 32 months for stage 4 (stage 4 restricted to ≥18 months: 39 months). The median age at diagnosis of stage 4S disease was 2.5 months for all 482 registered patients.
The time from the first reported symptom to the final neuroblastoma diagnosis was 13 days in stage 4S; 21 days in low- and intermediate-risk disease; 30 days in stage 4 cases aged ≥18 months; and 24 days for all patients. Asymptomatic cases were excluded for this calculation. The frequency of asymptomatic cases, found during routine examinations of the health status or for unrelated medical conditions, increased continuously from 12% (1980–1985) to a maximum of 44% during 1995–1999 (main screening period). From 2000 to 2014, the frequency of patients without symptoms remained high (34–36%).
Frequencies of Primary and Metastatic Sites
The percentage of patients with an unknown primary tumor site decreased from 4.2 to 0.8% (Table S6 in the ESM). A total of 50% of the primaries were found at the adrenal site, 29% at other abdominal sites (including pelvic), 16% at thoracic sites, and 4% at cervical sites. The order of the frequencies for the primary sites remained stable throughout the trials.
The frequencies of metastatic sites are listed in Table S7 in the ESM. Stage 4 patients aged ≥18 months presented with bone marrow metastases in 89% and bone metastases in 65% of cases. Lymph nodes were involved in 21% of cases, liver in 13%, intracranial sites in 6%, lungs or pleura in 5%, and skin in <1%. In total, 95% of all patients had metastases in the bone marrow and/or bones (osteomedullary). This figure was remarkably stable over the trials (range 92–98%). Time trends were observed for an increased detection of metastases in bone marrow (by cytology plus imaging techniques) and in lung/pleura sites. A decreasing frequency was seen for liver metastases and bone lesions.
Frequencies of Risk Factors
Determination of MYCN amplification has been recommended as the initial diagnostic tool for neuroblastoma since 1990. In total, 9% of patients with localized neuroblastoma, 10% with stage 4S disease, and 40% of children with stage 4 aged <18 months had MYCN-amplified neuroblastoma (Table 3). The combined low- and intermediate-risk group (stages 1–3 all ages, stage 4S, stage 4 aged <18 months) had MYCN amplification in 13% of the cases. Clinical high-risk neuroblastoma (stage 4 aged ≥18 months) showed MYCN amplification in 31% of cases. In this subgroup, an increase from trial NB97 (27%) to trial NB2004 (35%) was observed (p = 0.026). All other differences were not statistically significant.
Table 4 demonstrates that abnormal elevations of LDH (in 60% of the patients), ferritin (in 36% of the patients), and chromosome 1p aberrations (in 28% of the patients) were found across all patients. Children with low- and intermediate-risk disease (stages 1–3, stage 4S, stage 4 aged <18 months) had fewer LDH abnormalities (46%), ferritin elevations (24%), and chromosome 1p aberrations (21%) than patients with stage 4 aged ≥18 months (LDH abnormal in 92%, ferritin in 64%, and chromosome 1p aberrant in 50%). With the exception of the screening period that included more low-risk patients (trial NB97), the proportions of abnormal LDH, ferritin, and chromosome 1p aberrations did not differ between the studies, indicating that the risk profile of the patients with neuroblastoma was mostly constant throughout the trials.
Remission Proportions after Induction Chemotherapy
Figure 2 shows the categories of achieved remission after induction chemotherapy for patients with stage 4 disease who were aged ≥18 months by trial. Considering all trials together, 16% of patients achieved complete or very good partial remission after initial chemotherapy (range 6–29%), and 78% achieved partial or mixed remission or stable disease (range 61–89%). In 6% (range 2–10%), the tumor progressed or death occurred. Considerable fluctuations between the trials were observed; however, trends for improvements over time were not detected.
Frequencies of Extent of Primary Tumor Resections
Complete macroscopic removal with and without microscopic residuals was achieved in 64% of 3985 evaluable patients (all stages, best result counted in case of more than one operation). A total of 22% had an incomplete resection at best, and 14% of patients had a biopsy. Comparing trials NB97 and NB2004, the number of complete resections decreased (from 70 to 55%), whereas the proportion of incomplete resections increased (from 20 to 23%) and the proportion of biopsies increased (from 10 to 22%).
Details of the resectability for the regional stages 1, 2, 3, and for stage 4S are not presented in this report because of the impact of spontaneous regression on the surgical decision. For patients with stage 4 disease aged ≥18 months, in 63% of the patients, the primary tumor was completely removed; in 27%, there was incomplete resection; and in 10% of the patients, only a biopsy was performed. Complete resections reached a maximum of 75% in trial NB97 (incomplete resections 18%, biopsies 7%) but decreased in the most recent trial NB2004 (58% complete, 32% incomplete, 9% biopsy) (Fig. 3).
Frequencies of Sparing Chemotherapy for Patients with Low- and Intermediate-Risk Disease
The concept of avoiding chemotherapy has been applied to an increasingly greater number of patients (Tables S2 and S3 in the ESM). Figure 4 shows the increasing percentage of patients who never received chemotherapy, neither at initial treatment nor, in the event of recurrence or progression, for second-line therapy. In trials NB79 and NB82, 17% of patients with stage 4S and 35% of stage 1–3 disease (all ages) received no chemotherapy. The figures increased to 41% for stage 4S and to 60% for stages 1–3 (NB2004).
Event-Free and Overall Survival
The 10-year EFS of all 4463 patients was 57%, increasing from 44% (NB79) to 55% (NB2004). The 10-year OS was 67% for all patients, increasing from 46% (NB79) to 72% (NB2004) (Fig. 5a, b; Tables S8 and S9 in the ESM).
Survival by Stage
Children with localized neuroblastoma (stages 1–3) had similar rates of EFS throughout the trials. OS increased by roughly 8% (Table S9 in the ESM), although the therapeutic intensity decreased (Table S2 in the ESM).
Infants with stage 4S had a 10-year EFS of 74% and a 10-year OS of 85%. The lowest 10-year EFS was 67% (NB82), and the highest was 76% (NB97 and NB2004). The 10-year OS proportions increased from 71% (NB82) to 87% (NB2004) despite reduced chemotherapeutic intensity (Table S3 in the ESM).
Stage 4 patients aged ≥18 months with and without MYCN amplification improved from a 3% 10-year EFS (NB79) to 29% (NB97) and 24% (NB2004). The 10-year OS increased from 2% (NB79) to 33% (NB97) and 38% (NB2004) (Fig. 5c, d; Tables S8 and S9 in the ESM).
Survival by MYCN Amplification
Figure 5e, f demonstrate that the outcome was inferior for patients with MYCN amplification and stage 4 aged ≥18 months (10-year EFS 21%, 10-year OS 26%) compared with stages 1, 2, 3, 4S, and 4 aged <18 months (10-year EFS 37%, 10-year OS 48%) (log-rank test for EFS p = 0.005, for OS p = 0.002). In the MYCN-amplified group, the EFS was not influenced by single stages 1, 2, 3, and 4S (range 40–51%), with the exception of patients with stage 4 disease aged <18 months, who had a lower 10-year EFS (29%) (Table S8 in the ESM). In contrast, OS was stage dependent in MYCN-amplified cases: the 10-year OS was 92% for stage 1, 57% and 56% for stages 2 and 3, 41% for stage 4S, and 37% for stage 4 aged <18 months (log-rank p < 0.001) (Table S9 in the ESM). Notably, the frequency of MYCN amplification in the group of patients with stage 4 aged <18 months was 40% (Table 3).
If the MYCN oncogene was non-amplified, children with stage 4 aged >18 months had clearly inferior EFS and OS compared with all other stage/age groups (Fig. S2, Tables S8 and S9 in the ESM). Recurrences or progression were not necessarily fatal in these cohorts, e.g., stage 3 neuroblastoma without MYCN amplification had a 10-year EFS of 64% and a 10-year OS of 86%.
Survival by the Grade of Remission in Stage 4 Aged ≥18 Months and High-Risk Patients
The impact of remission categories on survival is shown in Fig. 6a, b for the 1139 patients with stage 4 neuroblastoma aged ≥18 months (all trials NB79–NB2004). Children with partial remission/mixed response/stable disease (PR/MR/SD) had a 10-year EFS of 21% compared with 32% for those with complete remission (CR)/very good partial remission (VGPR) (log-rank test p = 0.002). The 10-year OS figures were 27% for PR/MR/SD and 36% for CR/VGPR (log-rank test p = 0.021).
The influence of the remission status on the survival was trial dependent and detectable for trials NB90 and NB2004 on EFS and for trials NB90, NB97, and NB2004 on OS. No impact on EFS was seen for trials NB79, NB82, NB85, and NB97, and no impact on OS for trials NB79, NB82, and NB85.
Data for detailed remission categories were available from the year 1990 onwards. The CR group was best for EFS and OS but was small (6.1% of patients). The EFS and OS curves did not differ from the CR and VGPR groups in trials NB90 and NB 2004. Only in trial NB97 did patients with CR have a better EFS and OS than patients with VGPR. Categories MR (2.4% of all patients) and SD (3.3% of all patients) were grouped together with the PR category (68.7%).
The high-risk group yielded a similar result: patients with PR/MR/SD had an inferior EFS and OS compared with patients with CR/VGPR (n = 1126; NB90, NB97, NB2004, log-rank p < 0.0001).
Survival by the Grade of Primary Tumor Resection in Stage 4 Patients Aged ≥18 Months
Figure 6c, d demonstrate that if “biopsy” was the best achieved operation result in patients with stage 4 disease aged ≥18 months, the 10-year EFS (10%) and 10-year OS (12%) were inferior compared with those with higher degrees of resection (incomplete removal: 20% EFS, 30% OS; macroscopically complete removal 24% EFS, 29% OS). Complete versus incomplete removal was not statistically different in the total stage 4 aged ≥18 months group or in single trials, with one exception: In the NB82 trial, complete resection (n = 32) had a better EFS and OS than did incomplete resection (n = 19) (log-rank for EFS p = 0.017, for OS p = 0.025).
Frequencies of Death from Toxicity
Table 5 shows a proportion of 6% for toxic death during the time of protocol therapy for patients with stage 4 neuroblastoma aged ≥18 months (maximum was 11.6% in trial NB85, minimum was 3.8% in trial NB2004). Most toxic deaths in this group were caused by chemotherapy (including myeloablative chemotherapy; 88%), some by surgical complications (9%), and rarely by other causes (3%). Children with stage 1, 2, 3, 4S, or stage 4 aged <18 months at diagnosis (low and intermediate group) had a proportion of 2% for toxic death (maximum was 9% in trial NB79, minimum was 1% in trial NB2004). Within this group, chemotherapy was the cause of toxic death in 41% of cases, surgical complications in 38%, and other events in 22%. The decrease in the frequency of toxic death in the more recent trials is significant. Inclusion of the tumor/toxicity cases (discrimination of the causes "by toxicity" and/or "by tumor progression" impossible) adds 2% to the high-risk and 1% to the group with stages 1, 2, 3, 4S, or 4 aged <18 months.
MYCN status has been available since 1990: the proportion of toxic deaths for high-risk patients was 4.4% (90% by chemotherapy, 9% by operation, 1% by other). Among children with normal MYCN status and clinically low and intermediate risks, the proportion of toxic deaths was 1% (22/2042; 54% by operations, 41% by chemotherapy, 5% by other causes).
Time Intervals between Chemotherapy Cycles as a Measure of Toxicity
The median time interval from day 1 of the first cycle to day 1 of the second chemotherapy cycle was 24 days (all trials). The time interval increased to 26 days from the second to the third cycle (day 1/day 1). The intervals were 21/23 days in trial NB79, 23/23 days for NB82, 26/28 days for NB85, 28/28 days for NB90, 23/24 days for NB97, and 24/25 days for NB2004.
Frequencies of Late Sequelae
The most frequent late sequelae among all 3869 patients surviving ≥1 year after diagnosis were renal dysfunctions (5.9%), hypothyroidism (4.7%), auditory impairment (4.1%), spine deformities (3.1%), second malignancies (2.0%), other growth abnormalities, e.g., short stature (1.8%), hepatic dysfunction (1.1%), cardiologic impairment (0.9%), and neurological sequelae (0.4%).
Table 6 demonstrates the frequencies restricted to the group of patients with stage 4 disease aged ≥18 months. The ranking order is similar but the frequency is significantly higher. Differences between the trials were noticed. Renal dysfunctions were most frequently observed in trial NB90 and decreased thereafter. In contrast, hypothyroidism and hearing impairment were increasingly detected. An exorbitant proportion of second malignancies (8.9%) was observed in trial NB90, mainly in the maintenance chemotherapy arm. They were diagnosed up to 22 years after diagnosis. After closing that arm, the risk dropped back to 1–2% (maximum follow-up time was 19 years).