Vectibix for the Treatment of Anal Cancer

In the 1980s, the treatment of choice for anal cancer was abdominal-perineal amputation, which included the removal of the anus, rectum and lymphatic drainage areas and a permanent colostomy. With this treatment, 5-year survival rates were 40-70%. In the following years, however, it was shown that anal cancer was a tumor that was sensitive to chemotherapy and radiation, so surgery was not the first choice and was only reserved for resistant cases or relapses. Concomitant chemo and radiotherapy based on the Mitomycin C - 5-FU regimen is currently the standard treatment for localized (except T1N0) and locally advanced cases. This statement is supported by two randomized studies that showed that the administration of chemoradiation with Mitomycin C - 5FU was better than radiation in monotherapy. The trial conducted by the United Kingdom Coordinating Committee on Cancer Research (UKCCCR) randomized 585 patients to receive radiotherapy (45 Gy in 4-5 weeks) or the same radiotherapy regimen coupled with 5-FU (1000 mg/m2 x 4 days or 750 mg/m2 x 5 days), for the first and last week of radiotherapy and Mitomycin C 12 mg/m2 on day 1. The 3-year local failure rate was 39% in the combined arm versus 61% with radiotherapy alone. There were no differences in the 3-year overall survival rate. On the other hand, in the study conducted by EORTC, 110 patients were distributed to receive radiotherapy (45 Gy in 5 weeks, with an overimpression of 15 Gy in the patients with CR and 20 Gy if PR) or radiotherapy plus 5-FU (750 mg/m2 days 1-5 and 29-33) associated to Mitomycin C (15 mg/m2 on day 1). The CR rate was significantly greater in the group treated with chemoradiation (80% vs. 54%). After 5 years of follow-up, there was still an 18% increase in the local control rate in favor of the group treated with chemoradiation.

More recently, the results of a phase II CALGB trial, suggests that the administration of induction treatment with two cycles of cisplatin-5FU (cisplatin 100 mg/m2 on days 1 and 29 and 5FU 1000 mg/m2 days 1-4 and 29-32) followed by chemoradiotherapy with 5-FU and Mitomycin C was very promising, especially in patients with a poor prognosis, with 50% of patients remaining colostomy and disease-free at 48 months. However, in a randomized study by the RTOG group, which included 682 patients, this strategy was compared with the classic concomitant chemoradiation with 5-FU (1000 mg/m2 days 1-4 and 29-32) and Mitomycin C (10 mg/m2 days 1 and 29). No differences in survival were found, but it was also detected that the colostomy rate was greater in the patients treated with the regimen containing Cisplatin (HR, 1.68; 95% CI, 1.07-2.65; P=.02). The authors concluded that induction with cisplatin was not superior to the traditional administration of 5FU-Mitomycin C with RT.

Epidermoid anal cancer is a tumor that often expresses the EGFR receptor. In an initial study with 21 cases, it was reported that there was EGFR expression in all the biopsies. In another study with 38 cases, it was found that 55% of the tumors expressed EGFR. No study has been published, however, which has investigated the efficacy of Panitumumab in this tumor. There is only one report of a refractory case in which cetuximab was administered together with CPT-11 with an excellent response.