Late divergence of survival curves in cancer immunotherapy trials: interpretation and implications

Late divergence of survival curves of treated patients and controls is commonly seen in successful cancer immunotherapy trials. Although late survival curve divergence may be caused by a delayed action of therapy, it may also be related to early effects of the treatment. We suggest that late survival divergence most often reflects a specific benefit of therapy for patients who suffer from a comparatively slow progression of disease. The occurrence of delayed survival curve divergence has important implications for the statistical analysis of immunotherapy trials. Thus, it leads to non-proportional hazard ratios that make commonly used statistical tests, e.g., the logrank test, suboptimal. It is therefore suggested that the statistical analysis of immunotherapy trials primarily should be based on a test that compares the survival curves at or after a prespecified, fixed, late time point.

Effect of radiation therapy on survival in surgically resected retroperitoneal sarcoma: a propensity score-adjusted SEER analysis

BACKGROUND

Currently no prospective randomized trial has measured the efficacy of radiation therapy for resected retroperitoneal sarcomas (RPS). Our objective was to determine the effect of radiation therapy on disease-specific and overall survival between propensity score-matched surgically resected RPS patients using the Surveillance, Epidemiology, and End Results (SEER) database.

PATIENTS AND METHODS

The study population consisted of patients with histologically confirmed RPS who underwent surgical resection between 1988 and 2006. Exclusion criteria included multiple malignancies, distant metastasis, and unknown grade or stage. Cox modeling was used to determine covariate associations with disease-specific survival. Propensity score methods were used to perform survival analysis in patients who received radiation matched with patients who underwent surgery alone.

RESULTS

Prior to matching, there were 762 patients (558 surgery only, 204 surgery with radiation). Factors independently associated with radiation therapy were age (P = 0.037), geographic region (P = 0.041), grade (P = 0.047), stage (P = 0.003), and surgery type (P = 0.01). Cox modeling demonstrated that age, sex, grade, and stage were independently associated with survival. Propensity scoring (309 matched pairs) and survival analysis using Kaplan-Meier methods demonstrated no difference between propensity score-matched patients receiving radiation therapy and those who did not (P = 0.35).

CONCLUSION

At present, SEER patients with surgically resected RPS who received radiation therapy did not demonstrate survival benefit.

Readmission after pancreatectomy for pancreatic cancer in Medicare patients

OBJECTIVE

The objective of this study was to use a population-based dataset to evaluate the number of readmissions and reasons for readmission in Medicare patients undergoing pancreatectomy for pancreatic cancer.

METHODS

We used Surveillance, Epidemiology, and End Results-Medicare linked data (1992-2003) to evaluate the initial hospitalization, readmission rates within 30 days (early), and between 30 days and 1 year (late) after initial discharge and reasons for readmission in patients 66 years and older undergoing pancreatectomy.

RESULTS

We identified 1,730 subjects who underwent pancreatectomy for pancreatic cancer. The in-hospital mortality was 7.5%. The overall Kaplan-Meier readmission rate was 16% at 30 days and 53% at 1 year, accounting for 15,409 additional hospital days. Early readmissions were clearly related to operative complications in 80% of cases and unrelated diagnoses in 20% of cases. Late readmissions were related to recurrence in 48%, operative complications in 25%, and unrelated diagnoses in 27% of cases. In a multivariate analysis, only distal pancreatic resection (P = 0.02) and initial postoperative length of stay > or =10 days (P = 0.03) predicted early readmission. When compared to patients not readmitted, patients readmitted early had worse median survival (11.8 vs.16.5 months, P = 0.04), but the 5-year survival was identical (18%). Late readmission was associated with worse median and 5-year survival (19.4 vs. 12.1 months, 12% vs. 21%, P < 0.0001).

CONCLUSIONS

Our study demonstrates overall 30-day and 1-year readmission rates of 16% and 53%. The majority of early readmissions were related to postoperative complications but not related to patient and tumor characteristics. Complications causing early readmission are a cause of early mortality and are potentially preventable. Conversely, late readmissions are related to disease progression and are a marker of early mortality and not the cause.