Is pretreatment with chemotherapy effective at shrinking colon tumors?

This study examined how effective pretreatment with chemotherapy is at shrinking colon tumors. The study also investigated how comparable internal examination and external imaging are at grading the patients’ tumor.

For patients with locally advanced colon cancer, preoperative chemotherapy (neoadjuvant chemotherapy) is a new therapeutic approach. Doctors aim to only provide neoadjuvant therapy to patients who need it. This minimizes the risk of overtreatment of patients with less advanced tumors.

A number of tests are performed to diagnose which patients have sufficiently advanced tumors to need neoadjuvant chemotherapy. The clinician can perform an endoscopy (nonsurgical procedure which can be used to examine the digestive tract from the inside) to visualize the colon and take samples (biopsy) for laboratory analysis. This information is then used to grade the colon tumor (grade T1 to T4 – an indicator of how quickly the tumor is likely to spread) and the level of spread to the lymph nodes (grade N0-N2). Non-invasive images can also be taken using a computed tomography (CT) scan (a type of x-ray) to classify the tumor grade and lymph node grade. The accuracy of these techniques is essential for accurately choosing patients who will benefit from neoadjuvant therapy.

This study included 44 patients with locally advanced colon cancer who received neoadjuvant chemotherapy (oxaliplatin [Eloxatin] and fluoropyrimidines [such as Efudex]). All patients were staged before and after receiving neoadjuvant chemotherapy. Diagnosis consisted of a physical examination, endoscopy with biopsy (pathology report) and computed tomography (CT) scan. The more precise positron emission tomography/CT (PET/CT) scan (an imaging test that uses a radioactive substance, known as a tracer, to look for disease) was also performed for 15 patients.

At the beginning of the study 29 patients (65.9%) had stage II colon cancer, indicating that the tumor has spread to the outermost layer of the intestine but has not yet spread to the nodes. 15 patients (34.1%) had stage III cancer, indicating that the cancer has spread to the nodes but has not reached distant organs. The disease did not progress for any patients over the course of chemotherapy treatment.

Based on the CT scans all patients achieved tumor reduction after chemotherapy. The average tumor volume was 51.0 cc before chemotherapy and 18.4 cc after treatment. The tumor volume decreased by over 50% in 61.9% of patients.

The CT report supported the results from the pathology report well. It accurately classified the tumor grade in 62% of cases and lymph node grade in 87% of cases. The overall accuracy for the combined tumor and node grade was 77.3%, 13.6% of patients were under-staged and 9.1% were over-staged.

The authors concluded that neoadjuvant chemotherapy induced major tumor shrinkage. The CT scan showed a high accuracy and a low over-staging rate in patients with locally advanced colon cancer.

This is an early study with a relatively small number of patients. Future studies are needed to determine the best imaging method required to achieve the highest possible accuracy.