Stereotactic body radiotherapy for patients with oligometastases from colorectal cancer: risk-adapted dose prescription with a maximum dose of 83–100 Gy in five fractions

Abstract

We previously reported that the local control of pulmonary metastases from colorectal cancer (CRC) following stereotactic body radiotherapy (SBRT) with moderate prescription dose was relatively worse. We investigated the treatment outcomes and toxicities of patients with oligometastases from CRC treated by SBRT using risk-adapted, very high- and convergent-dose regimens. Among patients referred for SBRT from August 2011 to January 2015, those patients were extracted who had liver or pulmonary metastases from CRC, and they were treated with a total dose of 50–60 Gy in five fractions prescribed to the 60% isodose line of the maximum dose covering the surface of the planning target volume. Concurrent administration of chemotherapy was not admitted during SBRT, while neoadjuvant or adjuvant chemotherapy was allowed. A total of 21 patients (12 liver, 9 lung) with 28 oligometastases were evaluated. The median follow-up duration was 27.5 months (range: 6.5–43.3 months). Four patients were treated with SBRT as a series of initial treatments, and 17 patients were treated after recurrent oligometastases. The local control rates at 1 and 2 years from the start of SBRT were 100%. The disease-free and actuarial overall survival rates were 62% and 55%, and 79% and 79%, respectively. No severe toxicities (≥grade 3) occurred during follow-up. The outcomes following high-dose SBRT were excellent. This treatment can provide an alternative to the surgical resection of oligometastases from CRC. Prospective studies are needed to validate the effectiveness of SBRT.

Effect of primary tumor location and tumor size on the response to radiotherapy for liver metastases from colorectal cancer

“…Hypofractionated radiotherapy at higher doses per fraction may increase radiation-induced damages due to direct cytotoxicity, and may lead to microvascular disruption (38)(39)(40)(41). It was suggested that liver metastases should be treated by ablative SBRT as often as possible, and the present data support the findings reported in previous studies (15,16). In the present study, adding margins >8 mm to the ITV led to improved outcomes, although the differences were not significant.…”

“…However, the resection rate of hepatic metastases has been reported to be only 0.8-22% (25). Liver metastases are known to have different sensitivities to radiation therapy based on the location of the primary tumor; it has been reported that liver metastases derived from CRCs were significantly more resistant to radiation compared with liver metastases derived from non-colorectal cancers (15)(16)(17). Thus, patients with CRC metastases may benefit from dose escalation.…”

“…In the present study, adding margins >8 mm to the ITV led to improved outcomes, although the differences were not significant. When performing SBRT for liver tumors, no margins are usually added to the ITV (12)(13)(14)(16)(17)(18)(19)(20)(21)23). However, only a few studies have demonstrated how many GTV-to-CTV expansions are required in order to reach the gross and microscopic diseases in liver metastasis (41,42).…”

“…SBRT, also termed stereotactic ablative radiation therapy, is a proven curative treatment for medically inoperable small tumors in the lung and liver; it delivers highly conformal radiation in a limited number of high-dose fractions, providing excellent primary tumor control with minimal toxicity (12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Radiotherapy in alternatively fractionated regimens with a greater number of fractions may be required to reduce the biologically effective doses (BEDs) to normal tissues when treating liver tumors located in the hepatic portal regions.…”

Safety and efficacy of microwave ablation for medically inoperable colorectal pulmonary metastases: Single‐centre experience

“…Treatment alternatives for patients unsuitable for surgery are limited. Stereotactic body radiation therapy (SBRT) has recently been added to the treatment armamentarium of CRC lung metastases . Although RFA has been used as a treatment alternative for pulmonary oligometastases, this approach has fundamental limitations due to lung tissue properties.…”