The invited discussant of PRODIGE 13 was Tim Price, MBBS, DHthSc, Professor at the University of Adelaide, Australia, senior consultant medical oncologist, and Director of Medical Oncology and Clinical Cancer Research at the Queen Elizabeth Hospital. As he reminded listeners, the current ASCO guidelines recommend, at the basic level, CEA assessments every 6 months for at least 3 years, chest x-ray and abdominal ultrasonography twice in the first 3 years, and surveillance colonoscopy once in the first 1 to 2 years after surgery.1 These steps can be further enhanced by extending the duration of monitoring and by adding CT scans.
Tim Price, MBBS, DHthSc
ASCO guidelines aside, Dr. Price added, the recent Cochrane meta-analysis of studies using a variety of protocols found no significant advantage at this point in time for intensive monitoring (hazard ratio = 0.91).2
In PRODIGE 13, the control arm was already “a relatively intensive imaging protocol. This was not a low-use protocol, compared with the investigational arm,” he noted. Patients were randomly assigned to CEA or no CEA, then further randomly assigned to two radiologic protocols of greater and lesser intensity.
It is possible that the significant proportion of the population with stage II disease—about 50%—may have impacted the survival outcomes, noted Dr. Price. Patients with stage II disease have a relatively good prognosis despite surveillance, he added.
Although there were no differences in 5-year overall or recurrence-free survival within the time frame of the study, the use of CEA and CT did lead to more curative-intent surgery. “Remember, though, the starting point was a reasonably intensive protocol anyway,” Dr. Price pointed out.
“We also have to remember that care in 2020 is very different,” Dr. Price continued. Recent improvements in care include increased surgical interventions, interventions for oligometastatic disease, and improved systemic therapy after second surgeries. “What will be the impact of these surgeries on survival? Increasing the odds of early diagnosis may well have an impact on overall survival in the current setting, so this [improvement in resections] is an important outcome.”
Clinical Implications
Thus, Dr. Price recommended that clinicians continue to follow ASCO guidelines and not de-intensify surveillance. Ideally, clinicians will someday be able to select more intensive follow-up for higher-risk patients for whom early diagnosis will likely impact survival, perhaps by using circulating tumor DNA to guide monitoring. The greater use of targeted drugs for certain subsets will also further improve survival, he predicted.
DISCLOSURE: Dr. Price has served as a consultant or advisor to Amgen; has served as an institutional consultant or advisor to Merck Serono and Roche; has received institutional research funding from Amgen; and has been reimbursed for travel, accommodations, or other expenses by Amgen.
REFERENCES
1. Costas-Chavarri A, Nandakumar G, Temin S, et al: Treatment of patients with early-stage colorectal cancer: ASCO resource-stratified guideline. J Glob Oncol 5:1-19, 2019.
2. Jeffery M, Hickey BE, Hider PN: Follow-up strategies for patients treated for non-metastatic colorectal cancer. Cochrane Database Syst Rev 9:CD002200, 2019.
