Online Adaptive stereotactic radiotherapy for abdominopelvic lymphnode oligometastasis.

Oligometastasis is decribed as an an intermediate state of cancer spread
between localized disease and widespread metastases. They may arise from
distinct type of primaries such as (sarcoma, breast cancer, colorectal cancer,
etc,) and if lymph node involvement is not associated with an important
concomitant metastatic spread, it is reasonable to offer a chance of cure with
radical intent.
Metastases in lymph node(s) after primary treatment is considered a sign of
disease dissemination and as such is rarely approached with local treatment
like surgery or limited-field radiotherapy. Systemic therapy like chemotherapy,
endocrine treatment or new biological agents are considered the golden standard
in patients with lymph node recurrent cancer. Online-adaptive SBRT is a
modality therapy that utilizes stereotactic principles for dose localization
and delivers multiple beams to well defined targets in a few fractions. As a
result, this technique can deliver higher doses to tumors due to reduced
mechanical error margins, and thus cause less normal tissue damage.
A Ct scan will be made before the start of each fraction with online-adaptive
SBRT, and the treatment can be adapted by treating with another treatment plan.
Before the start of treatment, 2 or 3 other treatment plans (B, C, D) will be
made. At the moment of treatment, a treatment plan B, C, or D can be chosen if
the treatment plan gives more dose to the tumor and/or the organs at risk
receive less dose. If there is no gain with treatment plan B, C of D then the
standard plan A will be used for the treatment.

To determine local control of SBRT treatment for abdominopelvic oligometastasis
based on a fractionation scheme of 45 Gy in 5 fractions, to evaluate local
control, survival and toxicity. Use of the plan of the day as a tool for
optimize tumor coverage and minimize toxicity.

Non-randomized single arm of a prospective phase II study of SBRT for
abdominopelvic lymph node metastases.

Before every fraction of the radiotherapy, a CT scan will be made.

The current evidence for Stereotactic Radiotherapy for treatment abdominopelvic
lymphnode oligometastases is based on small retrospective and prospective data.
It is a feasible treatment, with local control rates at 2 years ranging from
64-77%.
With SBRT, the gastrointestinal tract is one of the most important
dose-limiting organs. Bowel toxicity might present with acute symptoms as
pain, nausea, vomiting, diarrhea and bleeding, as well as late toxicity
symptoms include chronic pain, diarrhea, stenosis and development of fistulas.
Grade 3 toxicity ranged from 3% up to 22%.
Two benefits are expected from the study: The first is a high local control due
to the on-line adaptive radiotherapy. An in-room Cone Beam CT (CBCT) scan
acquired just before dose delivery is used to select the treatment plan that
fits to the best observed anatomy in order to improve local control by creating
a better dose coverage of the PTV. The second benefit is to minimize toxicity
by reducing the dose in the organs at risk with the use of the plan of the day.