Dostarlimab a miraculous cure for mismatch repair-deficient, locally advanced rectal cancer?

Use of dostarlimab, a single-agent programmed death 1 (PD-1) monoclonal antibody, appears to have successfully cured mismatch repair-deficient, locally advanced rectal cancer, reports a recent study.

“Neoadjuvant chemotherapy and radiation followed by surgical resection of the rectum is a standard treatment for locally advanced rectal cancer,” the researchers said.

In this prospective phase II study, dostarlimab was administered every 3 weeks for 6 months in patients with mismatch repair-deficient stage II or III rectal adenocarcinoma, followed by standard chemoradiotherapy and surgery. Those who had a clinical complete response following completion of dostarlimab therapy would proceed without chemoradiotherapy and surgery.

Sustained clinical complete response 12 months after dostarlimab treatment or pathological complete response following dostarlimab therapy with or without chemoradiotherapy and overall response to neoadjuvant dostarlimab with or without chemoradiotherapy were the primary outcomes.

Twelve patients completed the dostarlimab treatment and underwent at least 6 months of follow-up. All of them (100 percent, 95 percent confidence interval, 74‒100) achieved a clinically complete response, with no evidence of tumour on magnetic resonance imaging, ¹⁸F-fluorodeoxyglucose–positron-emission tomography, endoscopic evaluation, digital rectal examination, or biopsy.

None of the patients had received chemoradiotherapy or undergone surgery at the time of this report. There were also no cases of progression or recurrence reported during follow-up (range 6‒25 months). In addition, grade ≥3 adverse events were not reported.

“Longer follow-up is needed to assess the duration of response,” the researchers said.