Oncologist Dr. Anelisa Coutinho explains a study presented at ASCO on the use of medication that
demonstrated 100% clinical response in a specific subgroup of patients with rectal cancer

When it comes to cancer, the greatest expectation is to have effective medications that can promote the cure of patients affected by this disease. Recently, the results of an important study dominated the national and international media in a surprising way.

This is a very small study that evaluated a medication called DOSTARLIMAB in patients with locally advanced rectal adenocarcinoma, stages II and III, with a genetic alteration
specifies: microsatellite instability or deficiency of DNA repair enzymes.

A microsatellites instability (MSI-H) it is an alteration found in less than 5% of patients with rectal cancer, i.e., approximately 95% of patients with this disease do not have this alteration. Based on data from studies on colorectal cancer and other tumors, it is known that patients with MSI-H are more susceptible to a form of treatment called immunotherapy, and DOSTARLIMAB It is a drug that belongs to this class of medications.

Treatment for locally advanced rectal cancer usually consists of radiation therapy, chemotherapy, and surgery. The idea of the authors of the work that was presented by Dr. Andrea Cercek at the largest American oncology congress, the ASCO congress, held in Chicago-USA this year, was to offer immunotherapy as initial treatment to patients with rectal cancer locally
advanced, assess the response after 6 months of treatment and only offer standard forms of treatment (radiotherapy, chemotherapy, followed or not by surgery) if there is no response to the experimental treatment.

The good surprise is that there was a complete clinical response, i.e. the absence of any evidence of residual tumor, in the first 14 patients evaluated.. The authors' expectation is to have a sample with at least 30 patients for this study, which is still ongoing. The number of patients is still small, the follow-up period after treatment is still short (median of 6.8 months), and
patients are still under observation. But without a doubt, this is already an excellent result, which can effectively modify the way of treating this special subgroup of patients with microsatellite instability, with a high response rate and saving them from side effects usually related to standard radiation therapy, chemotherapy and surgery.
Today, in oncological practice, microsatellite instability testing is already recommended for all patients with colorectal cancer, both for screening for a genetic syndrome called Lynch syndrome and to better guide treatment choices, as in the case of this study. The test is simple and widely available in many pathology laboratories, and is performed initially
in the tissue material from the tumor biopsy.

Science has evolved and we have learned to individualize treatments, identifying what best suits each patient and considering specific mutations that can be targeted by drugs aimed at these changes. The medical community and certainly the general population celebrated these results, which represent a lot and may favorably change the treatment perspective in this group of patients, but it should be noted that the still small number of
sample of the study, the prediction of a longer time for observing the results and the fact that it is applied to only a minority of patients with rectal cancer.

Anelisa K. Coutinho
Oncologist at AMO DASA
Member of SBOC, GTG, ASCO, ESMO