Patients with rectal cancer, in whom surgery is unable to completely remove the tumor, have a very poor prognosis and are generally considered incurable. There has, therefore, been an increasing interest for treating intermediate to advanced stage rectal cancer with preoperative radiation therapy, with the goal of shrinking the tumor and maximizing the probability that a curative surgical resection can be achieved. The dilemma has been in determining which patients benefit from this approach. Preoperative radiation is unnecessary in patients with early stage cancer, while it may be futile in patients with truly advanced cancer. In recent years, the development of endorectal ultrasound (EUS) has enabled more precise staging of patients before surgery. However, there has been relatively little data on the outcome of preoperative radiation therapy of patients staged via EUS.
In a recent study published in Cancer, doctors in Italy reported the results of a group of patients who were staged by EUS to have intermediate stage cancer treated with preoperative radiation. These patients all had tumor which has penetrated the muscular wall of the rectum. Patients were treated with twice daily radiation to a standard dose of 45 Gy over 3 weeks; a schedule designed to deliver a substantial radiation dose while not delaying the surgery.
The size of the cancer before radiation, as measured by EUS, was compared to the final cancer size in the surgical specimen. It was found that there was a decrease in cancer size among two-thirds of the patients, and the decrease averaged approximately one-third of the original cancer size. In 8.5% of the patients, there was no evidence of cancer remaining following radiation treatment, and 70% of patients had minimal remaining tumor cells. For 14% of patients who experienced shrinkage of cancer so that there was no longer any evidence of penetration through the muscular wall of the rectum in the surgical specimen (“pathological stage T1 or T0”), the cure rate at 2 years was 100%. In patients with pathological stage T2 (tumor involvement of muscle wall) or T3 (tumor penetration through the wall), the 2-year cure rates were 94 and 74%, respectively.
The treatment results reported in this study are impressive. The study demonstrates that preoperative radiation therapy in patients staged by EUS appears to be a valid approach. Longer follow-up is required to see whether these encouraging results hold up. Preoperative radiation for patients with EUS evidence of cancer penetrating the muscular wall of the rectum appears beneficial. Many patients with locally advanced rectal cancers who are unresectable currently are treated with a combination of chemo- and radiation therapy. It therefore remains to be seen whether the addition of chemotherapy will result in superior results compared to radiation alone before surgery. (Cancer, Vol 86, pp 398-404, 1999)
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