Feasibility and response of helical tomotherapy in patients with metastatic colorectal cancer

Abstract

Purpose: To investigate the treatment outcome and the toxicity of helical tomotherapy (HT) in patients with metastatic colorectal cancer (mCRC).

Materials and methods: We retrospectively reviewed 18 patients with 31 lesions from mCRC treated with HT between 2009 and 2013. The liver (9 lesions) and lymph nodes (9 lesions) were the most frequent sites. The planning target volume (PTV) ranged from 12 to 1,110 mL (median, 114 mL). The total doses ranged from 30 to 70 Gy in 10-30 fractions. When the α/β value for the tumor was assumed to be 10 Gy for the biologically equivalent dose (BED), the total doses ranged from 39 to 119 Gy10 (median, 55 Gy10). Nineteen lesions were treated with concurrent chemotherapy (CCRT).

Results: With a median follow-up time of 16 months, the median overall survival for 18 patients was 33 months. Eight lesions (26%) achieved complete response. The 1- and 3-year local progression free survival (LPFS) rates for 31 lesions were 45% and 34%, respectively. On univariate analysis, significant parameters influencing LPFS rates were chemotherapy response before HT, aim of HT, CCRT, PTV, BED, and adjuvant chemotherapy. On multivariate analysis, PTV ≤113 mL and BED >48 Gy10 were associated with a statistically significant improvement in LFPS. During HT, four patients experienced grade 3 hematologic toxicities, each of whom had also received CCRT.

Conclusion: The current study demonstrates the efficacy and tolerability of HT for mCRC. To define optimal RT dose according to tumor size of mCRC, further study should be needed.

Keywords: Colorectal cancer; Helical tomotherapy; Metastases.

Fig. 1. Planning target volumes (PTV) and biologically equivalent dose (BED) according to treatment site. Grey color indicates lesion without local progression; black color with local progression; others include bone, colon, seeding nodule, and pleural metastases. LN, lymph node.

Fig. 2. Local progression-free survival (LPFS), disease-free survival (DFS), and overall survival (OS) after helical tomotherapy for metastatic colorectal cancer.

Fig. 3. (A) Local progression-free survival (LPFS) according to planning target volume (PTV) after helical tomotherapy (HT) for metastatic colorectal cancer (mCRC) on univariate analysis. (B) LPFS according to biologically equivalent dose (BED) after HT for mCRC on univariate analysis. BED was calculated when the α/β value for the tumor was assumed to be 10 Gy.