In this large, population-based study of nearly 2,000 pancreatic cancer patients in the San Francisco Bay Area, vital status was confirmed in >99% of patients (using active and passive follow-up methods), allowing us to compute an overall 5-year survival rate of 1.3% and a median survival of 3.8 months. The 5-year survival rate and median survival time were greater in patients who were younger, were diagnosed with localized disease, had well-differentiated tumors, and had received surgical resection. Independent prognostic factors for poor survival were consistent with published data and included older age, male sex, distant or metastatic disease, and poorly differentiated tumor. In contrast, longer survival was observed among Asian/Pacific Islanders and patients who received any active treatment at the time of diagnosis.
We computed a lower overall 5-year survival rate (1.3%) compared with that reported in several population-based studies that used the National Cancer Database (19
) and SEER data (10
). Our 5-year survival rate also was lower for some patient subgroups including those diagnosed with localized disease and those who had undergone surgical resection, compared with rates reported from studies using SEER data and hospital or clinic-based data (19
). These differences may be partly explained by effects inherent to survival analysis methods where actuarial survival rates from the Kaplan-Meier method can differ from the actual survival rate when censoring is present. In the analysis of pancreatic cancer survival data, this would result in an increase in the 5-year survival rate with increasing number of censored patients (22
). Survival estimates also may be biased (higher) if the censoring (i.e., loss to follow-up) was correlated with patient death (e.g., poor survival and a large number of censored patients). Therefore, a possible explanation for our lower survival rate is that, unlike other studies, we used both active and passive follow-up of patients in our study, and it was nearly complete with less than 1% lost to follow-up. This allowed us to compute a “true” survival rate (actuarial survival rate of 1.3% vs. actual rate of 1.2%). Survival rate discrepancies also may be attributed to study design differences, as some studies excluded patients with a zero survival time (i.e., diagnosed at death or hours prior to death, whereas these patients were included in this study) and patients with missing demographic data or tumor/treatment characteristics. If these patients had shorter than average survival, their exclusion may have resulted in slight overestimates of the overall survival.
Similar to previous studies (11
), this study found that younger age, localized disease, well-differentiated tumors, and surgical resection were related to better survival and longer median survival time. Consistent with other studies (12
), our study also found that surgical or other treatment factors were significantly related to improved survival. Because treatment is related to stage at diagnosis, we further evaluated treatment by disease stage. Results showed that, regardless of stage at diagnosis, patients who had undergone surgical resection or had received radiation/chemotherapy or other treatments had better survival compared with those who received no active treatment or whose treatment was unknown. This suggests that active initial treatment may prolong survival, even for patients with advanced disease.
Although there were few long-term survivors and even fewer patients alive at last follow-up contact, our descriptive analyses agree with the results from the few other recent studies that have described the population of patients who have lived 5 years or longer (27
). Our results also showed that tumor extent and differentiation, as well as having had a tumor resection, are key survival-related factors of this patient subgroup. More detailed clinical data were not available that would have allowed us to further define these groups (i.e., lymph-node involvement). Our results and those of other studies found that patients who survived at least 5 years tended to be somewhat younger than the overall population of pancreatic cancer patients. As early onset cancers often have a hereditary component and can be more aggressive, it is unclear whether these younger long-term survivors have fewer comorbidities and/or have other underlying/correlated factors that affected their prognosis.
This large, population-based study included all pancreatic cancer patients diagnosed from 1995 to 1999 in 6 San Francisco Bay Area counties. Our use of active follow-up (contact of physicians’ offices, hospitals, patients’ relatives, and patients) in addition to passive follow-up including SEER vital statistics data allowed for a more complete vital status and survival assessment. Our use of active follow-up also allowed us to further evaluate long-term survivors to confirm their pancreatic cancer diagnosis, something that has been shown to be critical in small clinic-based studies (27
). Although we excluded few patients (n
= 18) after follow-up, our data suggest that, in a population with few long-term survivors, misclassification of pancreatic cancer among survivors combined with loss to follow-up can impact the overall survival rates. Further, because clinical data were obtained mainly from the cancer registry, many patients were missing clinical prognostic data, although our results were consistent with those of most previously published studies. These data likely reflect the low heterogeneity in pancreatic cancer stage at diagnosis, the few effective treatment options, and the lack of “curative” treatments—each a factor that influences cancer survival.
In summary, a lower overall survival rate was observed among patients diagnosed between 1995 and 1999 in our large, population-based study compared with estimates based on registry statistics alone. This may be attributed to a nearly complete determination of vital status and dates of death as a direct result of our use of extensive active follow-up of all pancreatic cancer patients diagnosed in 6 counties of the San Francisco Bay Area of California. Our results suggest that the poor pancreatic cancer survival rates have changed little over time. Consistent with other studies, this study found that localized disease and active treatment were the best predictors of longer survival. Early detection and improved treatment strategies are needed to improve prognosis for this deadly disease.