Adjuvant chemotherapy does not improve cancer-specific survival for pathologic stage II/III rectal adenocarcinoma after neoadjuvant chemoradiotherapy and surgery: evidence based on long-term survival analysis from SEER data

Effect of adjuvant chemotherapy on the oncological outcome of rectal cancer patients with pathological complete response

BACKGROUND

Locally advanced rectal cancer is typically treated using a combination of neoadjuvant chemoradiotherapy and total mesorectal resection. While achieving pathological complete response following neoadjuvant chemoradiotherapy has been recognized as a positive prognostic factor in oncology, the necessity of adjuvant chemotherapy for locally advanced rectal cancer patients with pathological complete response after surgery remains uncertain. The objective of this meta-analysis was to examine the impact of adjuvant chemotherapy on the oncological outcomes of rectal cancer patients who attain pathological complete response after neoadjuvant chemoradiotherapy.

METHODS

This meta-analysis followed the guidelines outlined in the preferred reporting items for systematic review and meta-analysis (PRISMA). The Web of Science, PubMed, and Cochrane Library databases were systematically searched to identify relevant literature.

RESULTS

A total of 34 retrospective studies, including 9 studies from the NCBD database, involving 31,558 patients with pathological complete response rectal cancer, were included in the meta-analysis. The included studies were published between 2008 and 2023. The pooled analysis demonstrated that adjuvant chemotherapy significantly improved overall survival (HR = 0.803, 95% CI 0.678-0.952, P = 0.011), and no heterogeneity was observed (I2 = 0%). Locally advanced rectal cancer patients with pathological complete response who underwent adjuvant chemotherapy exhibited a higher 5-year overall survival rate compared to those who did not receive adjuvant chemotherapy (OR = 1.605, 95% CI 1.183-2.177, P = 0.002). However, the analysis also revealed that postoperative ACT did not lead to improvements in disease-free survival and recurrence-free survival within the same patient population. Subgroup analysis indicated that pathological complete response patients with clinical stage T3/T4, lymph node positivity, and younger than 70 years of age may benefit from adjuvant chemotherapy in terms of overall survival.

CONCLUSIONS

The findings of this meta-analysis suggest that adjuvant chemotherapy has a beneficial effect on improving overall survival among rectal cancer patients with pathological complete response. However, no such association was observed in terms of disease-free survival and recurrence-free survival.

The benefits of adjuvant chemotherapy are associated with the kind of neoadjuvant therapy in stage ypI rectal cancer: evidence based on population analysis

PURPOSE

The oncological role of adjuvant chemotherapy (ACT) remains debated in locally advanced rectal cancer (RC) after neoadjuvant therapy (NAT), especially ypI RC. In this study, we used population-based data to evaluate the benefits of ACT in stage ypI RC after NAT and surgery. Moreover, we tried to differentiate what kind of NAT (radiotherapy alone or chemoradiotherapy) was administered because this may affect the further efficacy of ACT.

METHODS

All patients with stage ypI primary rectal malignancy were diagnosed in the SEER database between 2004 and 2017. The Kaplan-Meier method was applied to estimate the effects of ACT in survival analysis. Cox regression was performed to calculate the hazard ratio (HR) and the prognosis factors of survival. Propensity score matching (PSM) was used to balance the parameters between therapy groups.

RESULTS

The overall cohort's median follow-up time was 105 months. For 5-year OS and CSS, there were no significant differences between the ACT ( +) and ACT (-) groups (p = 0.105; p = 0.788). However, subgroup analyses according to the kind of NAT found that ACT improved overall survival (OS) and cancer-specific survival (CSS) in patients who received neoadjuvant radiotherapy (nRT) (p < 0.001, p = 0.015). Among patients who received neoadjuvant chemoradiotherapy (nCRT), no significant survival benefits were found between the ACT ( +) and ACT (-) groups (p = 0.526, p = 0.288).

CONCLUSION

Our population-based cohort study suggested that the efficacy of ACT was associated with the kind of NAT. The ACT provides survival benefits in stage ypI RC for patients who received nRT. However, among patients who received nCRT, ACT did not improve long-term survival.

Adjuvant chemotherapy improves long-term survival in pathologic stage III rectal mucinous adenocarcinoma after pre-operative chemoradiotherapy

PURPOSE

The benefits of adjuvant chemotherapy remain debated rectal mucinous adenocarcinoma (MC). Our study aims to delve into the efficacy of adjuvant chemotherapy in pathologic stage III rectal MC by a large population-based database.

METHODS

The Chi-square test was performed to examine the parameters between treatment groups. The overall survival (OS) and cancer-specific survival (CSS) of treatment groups were conducted by using the Kaplan-Meier method. The impact of factors on survival was assessed using Cox regression analyses. To balance the covariates and reduce the selection bias, we employed propensity score matching (PSM) to narrow the differences between treatment groups.

RESULTS

The median follow-up time for overall patients was 80 months. In the pre-operative chemoradiotherapy (pre-CRT) group, patients who received adjuvant chemotherapy had significantly better 5-year OS and CSS. Multivariate analyses found that adjuvant chemotherapy was associated with better OS (p < 0.001, HR (95% CI): 0.66 (0.51-0.86)) and CSS (p = 0.012, HR (95% CI): 0.71 (0.54-0.93)). However, adjuvant chemotherapy was not an independent prognosis factor in both OS (p = 0.149, HR (95% CI): 0.76 (0.53-1.1); Supplement Table 1) and CSS (p = 0.183, HR (95% CI): 0.74 (0.48-1.15)) in patients who did not receive pre-CRT. After PSM, similar results were found in the pre-CRT and the no pre-CRT groups.

CONCLUSION

In conclusion, our population-based retrospective cohort study indicates that the effects of adjuvant chemotherapy were associated with the pre-CRT status in patients with stage III rectal MC. In patients who underwent pre-CRT, the receipt of adjuvant chemotherapy was associated with better survival outcomes. Conversely, adjuvant chemotherapy does not seem to confer significant survival benefits to patients without pre-CRT.