Adjuvant chemotherapy is associated with improved overall survival in patients with rectal cancer and pathological complete response after neoadjuvant chemotherapy and resection, according to results from two studies of the National Cancer Database (NCDB).
The standard treatment for locally advanced rectal cancer includes neoadjuvant chemoradiation, surgical resection and adjuvant chemotherapy (ACT). The added impact of ACT on outcomes remains unclear, so patients who achieve a pathological complete response (pCR) are less likely to undergo ACT than those with residual disease after neoadjuvant therapy.
In one study, Dr. Sami A. Chadi from Toronto Western Hospital, in Canada, and colleagues used NCDB data to investigate whether ACT is associated with improved overall survival in 2,455 patients with pCR of their rectal cancer.
Just over a quarter of these patients received ACT, and 667 of these were paired with patients who did not receive adjuvant treatment for propensity-score-matched analyses.
Three-year and five-year overall survival rates were 97.6% and 95.0%, respectively, for patients treated with ACT and 94.0% and 88.2%, respectively, for patients who did not receive ACT, Dr. Chadi's team reports in JAMA Oncology, online April 19.
Clinically node-negative patients treated with ACT did not have significantly improved overall survival compared with those who did not receive ACT. In contrast, ACT was associated with significantly improved overall survival in clinically node-positive patients.
"Our study demonstrates that the use of adjuvant treatment should be considered in patients treated with neoadjuvant chemoradiotherapy who achieve pCR," the researchers conclude. "Recognizing the trade-offs between improving survival and the toxic effects of chemotherapy, the decision to administer ACT in this subset of patients with excellent survival should be individualized."
In the second study, also online April 19 in JAMA Oncology, Dr. Patricio M. Polanco from the University of Texas Southwestern Medical Center, in Dallas, and colleagues undertook a similar propensity-score-matched analysis of 741 pairs of patients with rectal cancer with pCR included in NCDB between 2006 and 2012.
Overall survival rates at one, three, and five years were 99.7%, 97.1%, and 94.7%, respectively, for the ACT group versus 99.2%, 93.6%, and 88.4% for the group that did not receive ACT.
In subgroup analyses, patients with clinical stage T3/T4, especially those with node-positive disease, benefited from ACT, although there was no significant overall survival difference among T/N subgroups.
Dr. George J. Chang from the University of Texas MD Anderson Cancer Center, in Houston, who wrote an editorial accompanying the reports, told Reuters Health by email, "I think we should take a critical view when interpreting the findings of observational studies of treatment effect on survival within registry data and ask, 'Do the findings make sense and are there potential alternative explanations to the observed findings?' And given that the group of patients with pCR are also the patients with the most favorable prognosis with a low risk for recurrence, the toxicity risk of adjuvant chemotherapy is not insignificant and can have long-lasting adverse effects on quality of life."
"I don't think that we should alter our current management for patients with rectal cancer based on these findings," he said. "Data from randomized trials do not support these conclusions, particularly in this group of patients who have very favorable prognosis already and in whom the absolute benefit of adjuvant therapy would be expected to be very small."
"We often find larger effects during retrospective analysis of large registries because there are a number of factors that contribute to the decision for treatment that are not represented by the available data, leading to overestimation of treatment effects," he explained. "For example, healthier patients are more likely to receive adjuvant therapy. However, when we are able to employ methodology that can adequately account for such biases through appropriate statistical methodology, we see that many of these relatively large effects are no longer observed."
"We should continue to work to generate new evidence to help inform these decisions, including identifying the patients who are at risk and sparing those who are not," Dr. Chang said.
Dr. Chadi did not respond to a request for comments, and Dr. Polanco was unable to provide comments in time for publication.
SOURCE: https://bit.ly/2HQP9GF, https://bit.ly/2qZIFLN and https://bit.ly/2FhVOo5
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