Neoadjuvant accelerated concomitant boost radiotherapy and multidrug chemotherapy in locally advanced rectal cancer: a dose-escalation study.

OBJECTIVES

To determine the maximal and safely dose of preoperative radiotherapy and concurrently intensified chemotherapy regimen (raltitrexed plus oxaliplatin) in locally advanced rectal cancer patients.

METHODS

Patients with cT3-T4 and/or cN≥1 or locally recurrent rectal cancer were sequentially assigned to 4 treatment schedules of chemoradiation: standard radiotherapy (50.4 Gy/5.5 wk) plus raltitrexed (cohort A), accelerated radiotherapy (55 Gy/5 wk) plus raltitrexed (cohort B), standard radiotherapy plus raltitrexed and oxaliplatin (cohort C), accelerated radiotherapy plus raltitrexed and oxaliplatin (cohort D). Patients were treated in cohorts of 6 to 12 per group. The maximal tolerated dose was exceeded if more than one-third of patients in a given cohort experienced dose-limiting toxicity (DLT). DLT was defined as any grade ≥3 toxicity according to the Radiation Therapy Oncology Group criteria.

RESULTS

Forty-six consecutive patients were enrolled. In cohort A, 6 patients received the planned treatment with no DLT. In cohort B, 1 of 8 patients experienced a DLT. In cohort C, a DLT occurred in 2 of 6 patients and therefore, a cohort expansion was required. Three of 16 patients treated at this dose level experienced a DLT. In addition, cohort D was expanded and DLT was found in 4 of 16 patients. Therefore, the maximal tolerated dose was not exceeded at any treatment level.

CONCLUSIONS

An intensified regimen of chemoradiotherapy delivering raltitrexed and oxaliplatin concurrently with concomitant boost radiotherapy (55 Gy/5 wk) can be safely administered in patients with locally advanced rectal cancer. On the basis of these results, this intensified regimen could be tested in a phase II study.