Indications for Adjuvant Radiation after Radical Prostatectomy as Predicted by Artificial Intelligence-Derived Dominant Intraprostatic Lesion Volume

PURPOSE/OBJECTIVE(S)

In prostate cancer, PI-RADs scores of dominant intraprostatic lesions (DILs) in multi-parametric magnetic resonance imaging (mpMRI) are prognostic; however, their inter-observer agreement is only moderate. Artificial intelligence (AI) may be a powerful tool for prognostication by analyzing a large number of scans consistently in a short amount of time. This study investigated whether the DIL volume (DILvol) provided by an AI deep-learning segmentation algorithm could predict adverse findings at radical prostatectomy (RP), some of which could warrant adjuvant radiation therapy (RT).

MATERIALS/METHODS

We conducted a retrospective study of 185 consecutive patients with localized prostate cancer who underwent an endorectal coil, high B-value (> = 1000 s/mm2), 3-Tesla mpMRI followed by RP between 2015 and 2017. Using a previously trained deep learning nnUNet algorithm for providing DIL segmentations from patients treated with definitive RT, we segmented the DIL for the RP cohort. We evaluated the association of AI DILvol with the risks of adverse pathologic factors, including positive margins, pathologic T3 (pT3) disease, and pathologic Gleason (pGS8-10) disease, using separate univariate logistic regression models. We then included AI DILvol, pT3 (vs pT2), pGS8-10 (vs pGS6-7), margin status, and pre-RP PSA for predicting post-RP PSA values utilizing multivariate linear regression analysis. Finally, we included these same factors into a multivariate logistic regression analysis for predicting the risk of meeting adjuvant RT indications (PSA persistence post-RP > = 0.1 ng/mL or positive lymph nodes).

RESULTS

The median time between RP and post-PSA value was 1.6 months. The Pearson's correlation coefficient between AI and reference DILvol (sum of manually contoured PI-RADS 3-5 lesions) was 0.86 (p < 0.001). The Pearson's correlation coefficient between AI DILvol and pathologic tumor size was 0.63 (p < 0.001). Utilizing separate univariate logistic regression models, we found that AI DILvol was significantly associated with the risks of positive margins (OR 1.31 [1.10, 1.58]; p = 0.003), pT3 (OR 1.59 [95% CI: 1.30, 1.99]; p < 0.001), and pGS8-10 (OR 1.28 [1.07, 1.56]; p = 0.01). On multivariate linear regression, AI DILvol (0.27/mL [0.25, 0.29]; p < 0.001) was significantly correlated with post-RP PSA values, after controlling for adverse factors and pre-RP PSA. On multivariate logistic regression, AI DILvol (adjusted OR 1.32 [1.05, 1.69]; p = 0.03) was the only factor significantly associated with the risk of meeting adjuvant RT indications after controlling for these same factors.

CONCLUSION

For localized prostate cancer treated with RP, AI DILvol was the only factor significantly associated with the risk of meeting adjuvant RT indications, even after controlling for pathologic factors at RP. Further studies are needed to determine if AI DILvol is prognostic for long-term oncologic outcomes after RP.

PSA Testing and Prostate Cancer Incidence Following the 2012 Update to the U.S. Preventive Services Task Force Prostate Cancer Screening Recommendation: Implications for Racial/Ethnic Disparities

The 2012 U.S. Preventive Services Task Force (USPSTF) recommendation against prostate specific antigen (PSA) testing led to a decrease in prostate cancer screening, but its impact on prostate cancer racial/ethnic disparities remains unclear. Methods: The proportion of men ages 40–74 years who received a routine PSA test in the past year was estimated over time in the Behavioral Risk Factor Surveillance System (BRFSS; 2012–2018) and the National Health Interview Survey (NHIS; 2005–2018). Screening trends by race/ethnicity were evaluated using logistic regression models to estimate odds ratios (ORs) of screening adjusting for socioeconomic and healthcare-related factors. Prostate cancer incidence rates and rate ratios (IRRs) by race/ethnicity were estimated in the Surveillance, Epidemiology and End Results (SEER) registry data over time (2004–2016). Results: In the 2012 BRFSS, PSA testing rates were highest among non-Hispanic white (NHW) men (32.3%), followed by non-Hispanic black (NHB; 30.3%), Hispanic (21.8%), and Asian/Pacific Islander men (17.7%). The absolute screening frequency declined by 9.5% overall from 2012 to 2018, with a greater decline among NHB (11.6%) than NHW men (9.3%). Adjusting for socioeconomic and healthcare-related factors, the relative decline was greater among NHB (OR per year = 0.86, 95% CI 0.84–0.88) than NHW men (OR = 0.89, 95% CI 0.89–0.90; p-het. = 0.005), driven by a steeper drop among NHB men ages 40–54. In the NHIS, the 2012 update was associated with a 35% decrease in the odds of screening (OR = 0.65, 95% CI 0.51–0.82), though there was no annual change since 2012 (OR = 1.00, 95% CI 0.98–1.03). Trends in the NHIS did not differ by race/ethnicity. The NHB:NHW IRR for total prostate cancer increased from 1.73 in 2011 to 1.87 in 2012 and has remained elevated, driven by differences in the incidence of localized tumors. Disparity IRRs have been consistent since 2012 for other racial/ethnic populations. Conclusions: Although the frequency of prostate cancer screening varies by race/ethnicity, the impact of the 2012 USPSTF recommendation against PSA testing on screening trends did not robustly differ by race/ethnicity. Following 2012, there was a modest increase in the disparity for localized prostate cancer incidence between NHB and NHW men.

Racial disparities in prostate cancer outcome among prostate-specific antigen screening eligible populations in the United States

Background

In 2012, the United States Preventive Services Task Force (USPSTF) recommended against prostate-specific antigen (PSA) screening, despite evidence that Black men are at a higher risk of prostate cancer-specific mortality (PCSM). We evaluated whether Black men of potentially screening-eligible age (55-69 years) are at a disproportionally high risk of poor outcomes.

Patients and methods

The SEER database was used to study 390 259 men diagnosed with prostate cancer in the United States between 2004 and 2011. Multivariable logistic regression modeled the association between Black race and stage of presentation, while Fine-Gray competing risks regression modeled the association between Black race and PCSM, both as a function of screening eligibility (age 55-69 years versus not).

Results

Black men were more likely to present with metastatic disease (adjusted odds ratio [AOR] 1.65; 1.58-1.72; P < 0.001) and were at a higher risk of PCSM (adjusted hazard ratio [AHR] 1.36; 1.27-1.46; P < 0.001) compared to non-Black men. There were significant interactions between race and PSA-screening eligibility such that Black patients experienced more disproportionate rates of metastatic disease (AOR 1.76; 1.65-1.87 versus 1.55; 1.47-1.65; Pinteraction < 0.001) and PCSM (AHR 1.53; 1.37-1.70 versus 1.25; 1.14-1.37; Pinteraction = 0.01) in the potentially PSA-screening eligible group than in the group not eligible for screening.

Conclusions

Racial disparities in prostate cancer outcome among Black men are significantly worse in PSA-screening eligible populations. These results raise the possibility that Black men could be disproportionately impacted by recommendations to end PSA screening in the United States and suggest that Black race should be included in the updated USPSTF PSA screening guidelines.

Minimally invasive surgery and its impact on 30-day postoperative complications, unplanned readmissions and mortality

BACKGROUND

A critical appraisal of the benefits of minimally invasive surgery (MIS) is needed, but is lacking. This study examined the associations between MIS and 30-day postoperative outcomes including complications graded according to the Clavien-Dindo classification, unplanned readmissions, hospital stay and mortality for five common surgical procedures.

METHODS

Patients undergoing appendicectomy, colectomy, inguinal hernia repair, hysterectomy and prostatectomy were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Non-parsimonious propensity score methods were used to construct procedure-specific matched-pair cohorts that reduced baseline differences between patients who underwent MIS and those who did not. Bonferroni correction for multiple comparisons was applied and P < 0·006 was considered significant.

RESULTS

Of the 532 287 patients identified, 53·8 per cent underwent MIS. Propensity score matching yielded an overall sample of 327 736 patients (appendicectomy 46 688, colectomy 152 114, inguinal hernia repair 59 066, hysterectomy 59 066, prostatectomy 10 802). Within the procedure-specific matched pairs, MIS was associated with significantly lower odds of Clavien-Dindo grade I-II, III and IV complications (P ≤ 0·004), unplanned readmissions (P < 0·001) and reduced hospital stay (P < 0·001) in four of the five procedures studied, with the exception of inguinal hernia repair. The odds of death were lower in patients undergoing MIS colectomy (P < 0·001), hysterectomy (P = 0·002) and appendicectomy (P = 0·002).

CONCLUSION

MIS was associated with significantly fewer 30-day postoperative complications, unplanned readmissions and deaths, as well as shorter hospital stay, in patients undergoing colectomy, prostatectomy, hysterectomy or appendicectomy. No benefits were noted for inguinal hernia repair.

The prognostic role of preoperative serum C-reactive protein in predicting the biochemical recurrence in patients treated with radical prostatectomy

BACKGROUND

To assess the prognostic value of preoperative C-reactive protein (CRP) serum levels for prognostication of biochemical recurrence (BCR) after radical prostatectomy (RP) in a large multi-institutional cohort.

METHODS

Data from 7205 patients treated with RP at five institutions for clinically localized prostate cancer (PCa) were retrospectively analyzed. Preoperative serum levels of CRP within 24 h before surgery were evaluated. A CRP level ⩾0.5 mg dl(-1) was considered elevated. Associations of elevated CRP with BCR were evaluated using univariable and multivariable Cox proportional hazards regression models. Harrel's C-index was used to assess prognostic accuracy (PA).

RESULTS

Patients with higher Gleason score on biopsy and RP, extracapsular extension, seminal vesicle invasion, lymph node metastasis, and positive surgical margins status had a significantly elevated preoperative CRP compared to those without these features. Patients with elevated CRP had a lower 5-year BCR survival proportion as compared to those with normal CRP (55% vs 76%, respectively, P<0.0001). In pre- and postoperative multivariable models that adjusted for standard clinical and pathologic features, elevated CRP was independently associated with BCR (P<0.001). However, the addition of preoperative CRP did not improve the accuracy of the standard pre- and postoperative models for prediction of BCR (70.9% vs 71% and 78.9% vs 78.7%, respectively).

CONCLUSIONS

Preoperative CRP is elevated in patients with pathological features of aggressive PCa and BCR after RP. While CRP has independent prognostic value, it does not add prognostically or clinically significant information to standard predictors of outcomes.

Medical androgen deprivation therapy and increased non-cancer mortality in non-metastatic prostate cancer patients aged ≥66 years

PURPOSE

To examine the potential relationship between androgen deprivation therapy and other-cause mortality (OCM) in patients with prostate cancer treated with medical primary-androgen deprivation therapy, prostatectomy, or radiation.

METHODS

A total of 137,524 patients with non-metastatic PCa treated between 1995 and 2009 within the Surveillance Epidemiology and End Results Medicare-linked database were included. Cox-regression analysis tested the association of ADT with OCM. A 40-item comorbidity score was used for adjustment.

RESULTS

Overall, 9.3% of patients harbored stage III-IV disease, and 57.7% of patients received ADT. The mean duration of ADT exposure was 22.9 months (median: 9.1; IQR: 2.8-31.5). Mean and median follow-up were 66.9, and 60.4 months, respectively. At 10 years, overall-OCM rate was 36.5%; it was 30.6% in patients treated without ADT vs. 40.1% in patients treated with ADT (p < 0.001). In multivariable-analysis, ADT was associated with an increased risk of OCM (Hazard-ratio [HR]: 1.11, 95% Confidence-interval [95% CI]: 1.08-1.13). Patients with no comorbidity (10-year OCM excess risk: 9%) were more subject to harm from ADT than patients with high comorbidity (10-year OCM excess risk: 4.7%).

CONCLUSIONS

In patients with PCa, treatment with medical ADT may increase the risk of mortality due to causes other than PCa. Whether this is a simple association or a cause-effect relationship is unknown and warrants further study in prospective studies.

Incidence and determinants of 1-month mortality after cancer-directed surgery

BACKGROUND

Death within 1 month of surgery is considered treatment related and serves as an important health care quality metric. We sought to identify the incidence of and factors associated with 1-month mortality after cancer-directed surgery.

PATIENTS AND METHODS

We used the Surveillance, Epidemiology and End Results Program to study a cohort of 1 110 236 patients diagnosed from 2004 to 2011 with cancers that are among the 10 most common or most fatal who received cancer-directed surgery. Multivariable logistic regression analyses were used to identify factors associated with 1-month mortality after cancer-directed surgery.

RESULTS

A total of 53 498 patients (4.8%) died within 1 month of cancer-directed surgery. Patients who were married, insured, or who had a top 50th percentile income or educational status had lower odds of 1-month mortality from cancer-directed surgery {[adjusted odds ratio (AOR) 0.80; 95% confidence interval (CI) 0.79-0.82; P < 0.001], (AOR 0.88; 95% CI 0.82-0.94; P < 0.001), (AOR 0.95; 95% CI 0.93-0.97; P < 0.001), and (AOR 0.98; 95% CI 0.96-0.99; P = 0.043), respectively}. Patients who were non-white minority, male, or older (per year increase), or who had advanced tumor stage 4 disease all had a higher risk of 1-month mortality after cancer-directed surgery, with AORs of 1.13 (95% CI 1.11-1.15), P < 0.001; 1.11 (95% CI 1.08-1.13), P < 0.001; 1.02 (95% 1.02-1.03), P < 0.001; and 1.89 (95% CI 1.82-1.95), P < 0.001 respectively.

CONCLUSIONS

Unmarried, uninsured, non-white, male, older, less educated, and poorer patients were all at a significantly higher risk for death within 1 month of cancer-directed surgery. Efforts to reduce 1-month surgical mortality and eliminate sociodemographic disparities in this adverse outcome could significantly improve survival among patients with cancer.

Perioperative outcomes and hospital reimbursement by type of radical prostatectomy: results from a privately insured patient population

BACKGROUND

With the increasing use of robotic surgery in the United States, the comparative effectiveness and differences in reimbursement of minimally invasive radical prostatectomy (MIRP) and open prostatectomy (ORP) in privately insured patients are unknown. Therefore, we sought to assess the differences in perioperative outcomes and hospital reimbursement in a privately insured patient population who were surgically treated for prostate cancer.

METHODS

Using a large private insurance database, we identified 17,610 prostate cancer patients who underwent either MIRP or ORP from 2003 to 2010. The primary outcomes were length of stay (LOS), perioperative complications, 90-day readmissions rates and hospital reimbursement. Multivariable regression analyses were used to evaluate for differences in primary outcomes across surgical approaches.

RESULTS

Overall, 8981 (51.0%) and 8629 (49.0%) surgically treated prostate cancer patients underwent MIRP and ORP, respectively. The proportion of patients undergoing MIRP markedly rose from 11.9% in 2003 to 72.5% in 2010 (P<0.001 for trend). Relative to ORP, MIRP was associated with a shorter median LOS (1.0 day vs 3.0 days; P<0.001) and lower adjusted odds ratio of perioperative complications (OR: 0.82; P<0.001). However, the 90-day readmission rates of MIRP and ORP were similar (OR: 0.99; P=0.76). MIRP provided higher adjusted mean hospital reimbursement compared with ORP (US $19,292 vs. US $17,347; P<0.001).

CONCLUSIONS

Among privately insured patients diagnosed with prostate cancer, robotic surgery rapidly disseminated with over 70% of patients undergoing MIRP by 2009-2010. Although MIRP was associated with shorter LOS and modestly better perioperative outcomes, hospitals received higher reimbursement for MIRP compared with ORP.

The effect of age at diagnosis on prostate cancer mortality: a grade-for-grade and stage-for-stage analysis

OBJECTIVE

To evaluate the effect of advancing age on cancer-specific mortality (CSM) after radical prostatectomy (RP).

MATERIALS AND METHODS

Overall, 205,551 patients with PCa diagnosed between 1988 and 2009 within the Surveillance Epidemiology and End Results (SEER) database were included in the study. Patients were stratified according to age at diagnosis: ≤ 50, 51-60, 61-70, and ≥ 71 years. The 15-year cumulative incidence CSM rates were computed. Competing-risks regression models were performed to test the effect of age on CSM in the entire cohort, and for each grade (Gleason score 2-4, 5-7, and 8-10) and stage (pT2, pT3a, and pT3b) sub-cohorts.

RESULTS

Advancing age was associated with higher 15-year CSM rates (2.3 vs. 3.4 vs. 4.6 vs. 6.3% for patients aged ≤ 50 vs. 51-60 vs. 61-70 vs. ≥ 71 years, respectively; P < 0.001). In multivariable analyses, age at diagnosis was a significant predictor of CSM. This relationship was also observed in sub-analyses focusing on patients with Gleason score 5-7, and/or pT2 disease (all P ≤ 0.05). Conversely, age failed to reach the independent predictor status in men with Gleason score 2-4, 8-10, pT3a, and/or pT3b disease.

CONCLUSIONS

Advancing age increases the risk of CSM. However, when considering patients affected by more aggressive disease, age was not significantly associated with higher risk of dying from PCa. In high-risk patients, tumor characteristics rather than age should be considered when making treatment decisions.

Diabetes mellitus without metformin intake is associated with worse oncologic outcomes after radical nephroureterectomy for upper tract urothelial carcinoma

AIMS

Evidence suggests a detrimental effect of diabetes mellitus (DM) on cancer incidence and outcomes. To date, the effect of DM and its treatment on prognosis in upper tract urothelial carcinoma (UTUC) remains uninvestigated. We tested the hypothesis that DM and metformin use impact oncologic outcomes of patients treated with radical nephroureterectomy (RNU) for UTUC.

METHODS

Retrospective analysis of 2492 patients with UTUC treated at 23 institutions with RNU without neoadjuvant therapy. Cox regression models addressed the association of DM and metformin use with disease recurrence, cancer-specific mortality and any-cause mortality.

RESULTS

A total of 365 (14.3%) patients had DM and 194 (7.8%) patients used metformin. Within a median follow-up of 36 months, 663 (26.6%) patients experienced disease recurrence, 545 patients (21.9%) died of UTUC and 884 (35.5%) patients died from any cause. Diabetic patients who did not use metformin were at significantly higher risk of disease recurrence and cancer-specific death compared to non-diabetic patients and diabetic patients who used metformin. In multivariable Cox regression analyses, DM treated without metformin was associated with worse recurrence-free survival (HR: 1.44, 95% CI 1.10-1.90, p = 0.009) and cancer-specific mortality (HR: 1.49, 95% CI 1.11-2.00, p = 0.008).

CONCLUSIONS

Diabetic UTUC patients without metformin use have significantly worse oncologic outcomes than diabetics who used metformin and non-diabetics. The possible mechanism behind the impact of DM on UTUC biology and the potentially protective effect of metformin need further elucidation.

Accuracy of the EORTC risk tables and of the CUETO scoring model to predict outcomes in non-muscle-invasive urothelial carcinoma of the bladder

Background:

The European Organization for Research and Treatment of Cancer (EORTC) risk tables and the Spanish Urological Club for Oncological Treatment (CUETO) scoring model are the two best-established predictive tools to help decision making for patients with non-muscle-invasive bladder cancer (NMIBC). The aim of the current study was to assess the performance of these predictive tools in a large multicentre cohort of NMIBC patients.

Methods:

We performed a retrospective analysis of 4689 patients with NMIBC. To evaluate the discrimination of the models, we created Cox proportional hazard regression models for time to disease recurrence and progression. We incorporated the patients calculated risk score as a predictor into both of these models and then calculated their discrimination (concordance indexes). We compared the concordance index of our models with the concordance index reported for the models.

Results:

With a median follow-up of 57 months, 2110 patients experienced disease recurrence and 591 patients experienced disease progression. Both tools exhibited a poor discrimination for disease recurrence and progression (0.597 and 0.662, and 0.523 and 0.616, respectively, for the EORTC and CUETO models). The EORTC tables overestimated the risk of disease recurrence and progression in high-risk patients. The discrimination of the EORTC tables was even lower in the subgroup of patients treated with BCG (0.554 and 0.576 for disease recurrence and progression, respectively). Conversely, the discrimination of the CUETO model increased in BCG-treated patients (0.597 and 0.645 for disease recurrence and progression, respectively). However, both models overestimated the risk of disease progression in high-risk patients.

Conclusion:

The EORTC risk tables and the CUETO scoring system exhibit a poor discrimination for both disease recurrence and progression in NMIBC patients. These models overestimated the risk of disease recurrence and progression in high-risk patients. These overestimations remained in BCG-treated patients, especially for the EORTC tables. These results underline the need for improving our current predictive tools. However, our study is limited by its retrospective and multi-institutional design.

Risk stratification of pT1-3N0 patients after radical cystectomy for adjuvant chemotherapy counselling

BACKGROUND

In pT1-T3N0 urothelial carcinoma of the bladder (UCB) patients, multi-modal therapy is inconsistently recommended. The aim of the study was to develop a prognostic tool to help decision-making regarding adjuvant therapy.

METHODS

We included 2145 patients with pT1-3N0 UCB after radical cystectomy (RC), naive of neoadjuvant or adjuvant therapy. The cohort was randomly split into development cohort based on the US patients (n=1067) and validation cohort based on the Europe patients (n=1078). Predictive accuracy was quantified using the concordance index.

RESULTS

With a median follow-up of 45 months, 5-year recurrence-free and cancer-specific survival estimates were 68% and 73%, respectively. pT-stage, ge, lymphovascular invasion, and positive margin were significantly associated with both disease recurrence and cancer-specific mortality (P-values ≤ 0.005). The accuracies of the multivariable models at 2, 5, and 7 years for predicting disease recurrence were 67.4%, 65%, and 64.4%, respectively. Accuracies at 2, 5, and 7 years for predicting cancer-specific mortality were 69.3%, 66.4%, and 65.5%, respectively. We developed competing-risk, conditional probability nomograms. External validation revealed minor overestimation.

CONCLUSION

Despite RC, a significant number of patients with pT1-3N0 UCB experience disease recurrence and ultimately die of UCB. We developed and externally validated competing-risk, conditional probability post-RC nomograms for prediction of disease recurrence and cancer-specific mortality.

Distribution of metastatic sites in renal cell carcinoma: a population-based analysis

BACKGROUND

We assessed the distribution of site-specific metastases in patients with renal cell carcinoma (RCC) according to age. Moreover, we evaluated recommendations proposed by guidelines and focused specifically on bone and brain metastases.

PATIENTS AND METHODS

Patients with metastatic RCC (mRCC) were abstracted from the Nationwide Inpatient Sample (1998-2007). Age was stratified into four groups: <55, 55-64, 65-74 and ≥ 75 years. Cochran-Armitage trend test and multivariable logistic regression analysis tested the relationship between age and the rate of multiple metastatic sites. Finally, we examined the rates of brain or bone metastases according to the presence of other metastatic sites.

RESULTS

In 11,157 mRCC patients, the rate of multiple metastatic sites decreased with increasing age (P < 0.001). This phenomenon was confirmed in patients with lung, bone, liver and brain metastases (all P ≤ 0.01). The rate of bone metastases was 10% in patients with exclusive abdominal metastases and 49% in patients with abdominal, thoracic and brain metastases. The rate of brain metastases was 2% in patients with exclusive abdominal metastases and 16% in patients with thoracic and bone metastases.

CONCLUSIONS

The proportion of patients with multiple metastatic sites is higher in young patients. The rates of bone (10%-49%) and brain (2%-16%) metastases are nonnegligible in mRCC patients.

Emergence of rare sapovirus genotype among infants and children with acute gastroenteritis in Japan

A total of 1,154 fecal specimens from infants and children with acute gastroenteritis in five cities in Japan (Maizuru, Tokyo, Sapporo, Saga, and Osaka), collected from July 2003 to June 2005, were tested for the presence of diarrheal viruses by reverse transcriptase multiplex PCR. Overall, 469 of 1,154 (40.6%) were positive for diarrheal viruses, of which 49 (10.4%) were positive for sapovirus. The peak of sapovirus infection shifted from April-June in 2003-2004 to October-December in 2004-2005. The observations show that maximum sapovirus prevalence can occur during warmer seasons. Sapovirus was subjected to molecular genetic analysis by sequencing. The results indicated that sapovirus genogroup I was a dominant group (100%). Sapovirus strains detected in this study were further classified into four genotypes (GI/1, GI/4, GI/6, and GI/8). Of these, sapovirus GI/1 was the most predominant, followed by sapovirus GI/6; these accounted for 93% (13 of 14) and 7% (1 of 14), respectively, in 2003-2004. However, it was noteworthy that sapovirus GI/6 suddenly emerged to become the leading genotype, accounting for 77% (27 of 35) of isolates in 2004-2005. This is believed to be the first report of the changing distribution of sapovirus genotypes and of the emergence of the rare sapovirus GI/6.