The ASCRS Rectal Cancer Committee (RCC) wants to ensure that ASCRS members are aware of the small but exciting study published June 5, 2022, in the New England Journal of Medicine: PD-1 Blockade in Mismatch Repair-Deficient, Locally Advanced Rectal Cancer.(ref)  Cerek and colleagues from Memorial Sloan Kettering Cancer Center report on 12 patients with mismatch-repair-deficient clinical stage II or III rectal cancer treated with the PD-1 inhibitor dostarlimab.  Treatment was every 3 weeks for 6 months, and 100% of patients had a clinical complete response.  These patients are in a “watch and wait” protocol, and none have required chemoradiation or surgery at a median follow-up of 12 months.  It is important to note that only 5-10% of rectal cancers are mismatch-repair deficient.  Furthermore, careful “watch and wait” monitoring (in centers with established protocols for, and experience with, nonoperative management) is essential, given the uncertainty about the durability of these responses. 

https://www.nejm.org/doi/full/10.1056/NEJMoa2201445 
 
Reference:
Cercek A, Lumish M, Sinopoli J, Weiss J, Shia J, Lamendola-Essel M, El Dika IH, Segal N, Shcherba M, Sugarman R, Stadler Z, Yaeger R, Smith JJ, Rousseau B, Argiles G, Patel M, Desai A, Saltz LB, Widmar M, Iyer K, Zhang J, Gianino N, Crane C, Romesser PB, Pappou EP, Paty P, Garcia-Aguilar J, Gonen M, Gollub M, Weiser MR, Schalper KA, Diaz LA Jr. PD-1 Blockade in Mismatch Repair-Deficient, Locally Advanced Rectal Cancer. N Engl J Med. 2022 Jun 5. doi: 10.1056/NEJMoa2201445. Epub ahead of print. PMID: 35660797.