Editorial commentary
In the editorial, Dr. Sanoff emphasized that the approach remains experimental and should not replace current curative treatment. She noted that cancer recurrences have been seen in other studies using both chemotherapy and immunotherapy.
For example, with chemotherapy and radiation, those patients who achieve a clinical complete response have a better prognosis compared with those who do not, but she cautioned that “cancer regrowth occurs in 20% to 30% of such patients when the cancer is managed nonoperatively.”
Dr. Sanoff noted that recurrences were seen when this approach of PD-1 inhibition has been used for metastatic colorectal cancer with dMMR. In the KEYNOTE-177 trial with pembrolizumab (Keytruda), only 55% of patients were reported to be alive without cancer progression at 12 months, and of the patients who initially had a strong response, only 70% had an ongoing response 3 years later.
“These recurrence dynamics may (or may not) differ between immunotherapy and chemoradiotherapy and between early and late-stage disease,” Dr. Sanoff said.
“In fact, very little is known about the duration of time needed to find out whether a clinical complete response to dostarlimab equates to cure,” she added.
In addition, Dr. Sanoff warned that the decision not to pursue further treatment and to follow patients with observation alone requires very close monitoring.
The current study was conducted at a top U.S. cancer center, Memorial Sloan Kettering Cancer Center. The authors noted that the complete responses (after a minimum of 6 months of follow-up) were measured by the combination of rectal MRI, visual endoscopic inspection, and digital rectal examination.
The completeness of these responses was further supported by the absence of residual tumor on serial endoscopic biopsies and the resolution of 18F-fluorodeoxyglucose uptake on PET scans, the authors added.
In the editorial, Dr. Sanoff said that “safe nonoperative management [also] involves access to specialty care for direct intraluminal visualization and expertise in interpretation of rectal magnetic resonance imaging ... Such expertise is not available in all communities and without it, patients could miss the opportunity for curative resection if tumor regrowth occurred.”
The study was sponsored by the Simon and Eve Colin Foundation, GlaxoSmithKline, and Stand Up to Cancer, among others.
A version of this article first appeared on Medscape.com.