Shorter RT Schedule Effective, Less Toxic for Locally Advanced Rectal Cancer

A short-course of preoperative radiation therapy plus consolidated chemotherapy was shown to be as effective as standard preoperative chemoradiation in the treatment of locally advanced rectal cancer, according to the results of a phase III Polish study.

The study was presented at a presscast ahead of the 2016 American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium, held January 21–23 in San Francisco (abstract 489), by Lucjan Wyrwicz, MD, PhD, head of the medical oncology unit in the department of gastrointestinal cancer at the Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology in Warsaw.

The study compared preoperative 5 × 5 Gy (5 days by 500 cGy) plus consolidation chemotherapy with the standard treatment of a 5-week course of chemoradiation. Although the short-course schedule did not prove to be superior in terms of radical resection of the rectal tumor, the experimental group did have fewer acute toxicities compared with the standard therapy group (75% vs 83%; P = .006).

The trial included 515 patients with fixed cT3 or cT4 rectal cancer. Patients were randomly assigned to 5 × 5 Gy and three courses of FOLFOX4 after 1 week rest (n = 261) or to 50.4 Gy in 28 fractions given with a 5-FU bolus, leucovorin, and oxaliplatin (n = 254). Wyrwicz noted that after data showed no advantage of adding oxaliplatin to chemoradiation in 2012, the study protocol was amended and oxaliplatin could be omitted at the discretion of the participating study site.

The primary endpoint of the study was rate of radical resection. No significant difference was found between patients assigned the experimental therapy compared with the standard therapy (77% vs 71%; P = .081). In addition, there was no significant difference in the pathologic complete response rates for patients assigned the 5 × 5 Gy schedule compared with the standard therapy (16% vs 12%; P = .17).

Looking at the trial’s secondary endpoints, Wyrwicz said there were no significant differences in disease-free survival, incidence of local failures, or incidence of metastases. The 3-year overall survival rate was significantly higher for patients assigned the short-course schedule (73% vs 65%; P = .046). According to Wyrwicz, these results warrant additional investigation of this treatment approach.

Commenting on these results Smitha Krishnamurthi, MD, ASCO Spokesperson and moderator of the presscast said, “This demonstrates that short-course radiation followed by chemotherapy can achieve a reduction in tumor as seen with a pathologic complete response of 16%, which is equal to that of chemoradiation. The short-course radiation had less acute toxicity than the chemoradiation; however, we must keep in mind that the chemoradiation included oxaliplatin, which has been shown to increase the toxicity of the regimen and is no longer part of standard chemoradiation.”