SMART Treatment

Any treatment that doubles the length of survival for cancer patients is a SMART treatment for any cancer, especially mesothelioma. The “SMART” treatment stands for Surgery for Mesothelioma After Radiation Therapy.1 Drs. Cho and colleagues tested the feasibility of treating mesothelioma with precisely delivered radiation therapy first, before surgery in 25 patients.1 The idea is to fry most of the mesothelioma cells with radiation therapy and then remove any remaining tumor and any damaged lung tissue.

SMART Results

After a 23 month follow-up period in the “SMART” treatment, the patients with epithelial mesothelioma had a 84% cumulative 3-year survival rate.1 However, patients with biphasic mesothelioma had a 13% cumulative 3-year survival rate.1

In comparison, two studies at two different hospitals (Turkey2 and Texas3) reported the outcomes of their mesothelioma patients after receiving surgery, then radiation therapy and chemotherapy.

The Turkish retrospective study2 reported that the different treatment regimens provided significantly different mean survival times in the 400 patients: Basic care group 10.5 months; Surgical group 15.7 months; Chemotherapy group range 14.5 months to 18.3 months; and Multimodality group 26.5 months2.

The Texan hospital reported that the mean survival time for the 88 mesothelioma patients who received radiation treatment was 14.7 months.3 They also reported that patients treated with IMRT after surgery (EPP) had low rates of mesothelioma recurring in the chest wall.3 However, lung toxicity was a problem for some patients.3

Radiation Therapy in the SMART Treatment: What is IMRT?

Cho et al1 used intensity modulated radiation therapy, called IMRT, to more closely focus the radiation beams to the actual tumor, in size and shape (3D). Basically, the machine that produces the radiation, a multileaf intensity-modulating collimator, is like a kaleidoscope, with each filter or color representing a leaf that diminishes the intensity of radiation in a specific beam or beamlet. Most multileaf intensity-modulating collimators have between 4 to 13 beams and each beam is divided into at least 3 beamlets.

The objective is to send radiation only onto mesothelioma tissue with very little going onto the adjacent normal tissues such as the lungs, heart or esophagus. However, there’s a little spillover, just like holding a flashlight very close to your pantleg—a little light leaks outside. In addition, mesothelioma grows on the lining of the chest cavity so as you breathe in and out, your chest cavity (and tumor) moves.

IMRT has at least three main advantages over regular radiation therapy: IMRT can conform the beams (and beamlets) of radiation to the size and shape of the tumor better than regular radiation. IMRT can reduce the amount of spillage of radiation onto adjacent normal tissue. IMRT allows a higher dose to be given to the tumor.

How Does IMRT Work?

First, the radiologist uses a 3 dimensional CT scan to determine the shape and location of the tumor as you breathe (sometimes called a 4 dimensional CT scan, with time as the fourth dimension). The 3D-CT scan or 4D-CT scan provides a map for the width, length, and depth of the tumor lesion, and the distance between the tumor and the adjacent normal tissue (called the margin).

Second, the radiologist(s) plan the treatment to minimize exposure to vital organs nearby like the esophagus, lungs, and heart with specially developed software. It determines how much radiation each beamlet projects into the diseased region (Projected Target Volume (PTV)). Thus, each person receives an individual treatment plan because each tumor size and location is slightly different.

Third, computer-controlled intensity modulation delivers the right amount of radiation to each beam and their beamlets to an immobilized patient during treatment.

Note, in some cases the oncologist will ask the patient to hold their breath for a few seconds during the actual delivery of the radiation. Holding your breath reduces movement of the tumor. It’s best for you to hold your breath in the same part of the cycle each time (always full of air, always after exhalation (no air), or always in the middle of breathing). To maximize the benefits and minimize the risks, hold it during whatever part of the breathing cycle the oncologist asks. This helps them make sure that the radiation targets your tumor as best as possible. The reason these instructions can vary is that the oncologist has figured out how much air you need in your chest cavity to have the maximum distance between the tumor and normal lung tissue.

Alternatively, they may ask that you breathe normally because their machine has been calibrated to give the right amount of radiation as you breathe normally.

Surgery

Cho et al1 reported that the extrapleural pneumonectomy was performed between 4 and 8 days after the completion of radiation.

Considerations

Because the SMART treatment regimen provided almost twice the overall survival time in patients with the epithelial mesothelioma1 as some other treatments,3,4 it warrants consideration and further testing. As a patient or healthcare provider, the type of mesothelioma seems to affect overall survival also.

The IMRT treatment is very dependent on the ability of the radiologist to target the tumor tissues while reducing the exposure to normal lung tissue to minimize lung toxicity.