LCD L39553: Radiation Therapies

Overview

Intensity Modulated Radiation Therapy (IMRT)

IMRT is a form of 3D conformal radiation therapy (3D-CRT) that changes the intensity of radiation within different parts of single radiation beams while the treatment is delivered. Thus, IMRT can simultaneously treat multiple areas within the target to different dose levels. It most commonly utilizes 5, 7, or 9 treatment beams from different directions, with each field being from a stationary direction, but in which the radiation output varies across the field with time of irradiation. IMRT is especially useful in radiating treatment targets positioned near other normal tissues that need exposure to be minimized.

Volumetric modulation arc radiotherapy (VMAT) is a form of IMRT in which the radiation source moves in an arc around the patient while delivering the radiation treatment. VMAT delivery is more efficient and can be given in half the usual time as compared to IMRT.

IMRT utilizes a treatment-planning technique called inverse planning. IMRT treatment plans are tailored to the target volumes and are more precise than conventional or CRT plans. Through a computerized optimization process, the physicist or dosimetrist enters the anatomic information of tumors and organs at risk (OARs), as detailed by the radiation oncologist, specifies the desired dosimetric outcome and its constraint for each structure of interest and then lets the computerized treatment-planning system identify the best beam orientation and intensity pattern over the treatment fields. After inverse planning, an optimized treatment plan is developed.

Delivery of IMRT may be done with various combinations of gantry motion, table motion, slice-by-slice treatment (tomotherapy) and multi-leaf collimator (MLC) or solid compensators to modulate the beam or arc intensities.

The treatment plan for IMRT must be carefully followed with each session. The required precision and accuracy exceed that of conventional RT. The radiation team of oncologists, medical physicists, medical dosimetrists and radiation therapists must be well-coordinated. Drawbacks to IMRT include the potential for dose heterogeneity within a specific structure. This heterogeneity is the trade-off for improved dose conformity. Also, IMRT involves an increased “integral dose” resulting from unintended radiation outside the intended treatment volumes due to the use of multiple, fixed fields or rotating arcs. The long-term risk of second malignancies from this integral dose is still unclear. 1

Stereotactic Radiosurgery (SRS)

SRS combines anatomic accuracy and reproducibility with very high doses of highly precise, externally generated ionizing radiation to optimally ablate or eradicate the target(s) in the head while minimizing collateral damage to adjacent tissues. “Stereotactic” means a target lesion is localized relative to a known 3-dimensional (3D) reference system. Markers might be used on or in the body such as seeds, clips, or surface markers. Devices used in SRS for stereotactic guidance could include rigid head frames affixed to the patient, fixed bony landmarks, implanted fiducial markers, or mask-based systems. Imaging, planning and treatment typically are performed in close temporal proximity. The delivery of a high dose of ionizing radiation that conforms to the shape of the lesion mandates an overall accuracy of approximately 1 mm. To assure quality of patient care, the procedure involves a multidisciplinary team consisting of a neurosurgeon, radiation oncologist, medical physicist, and radiation therapist. For some tumors involving the skull base, the multidisciplinary team may include a head and neck surgeon with training in SRS.

All SRS procedures include the following: position stabilization with or without a frame, imaging for localization, computer-assisted tumor localization (i.e., “image guidance”), treatment planning, isodose distributions/dose prescription/dose calculation, setup and accuracy verification testing, simulation of prescribed arcs or fixed portals, and radiation delivery.

Stereotactic Body Radiation Therapy (SBRT)

SBRT is also known as stereotactic ablative radiotherapy (SABR) or ultrahypofractionated RT.

SBRT is a treatment that couples a high degree of anatomic targeting accuracy and reproducibility with very high doses of extremely precise, externally generated, ionizing radiation. The therapeutic intent of SBRT is to maximize cell-killing effect on the target(s) while minimizing radiation-related injury in adjacent normal tissues.

SBRT is used to treat extra-cranial sites as opposed to SRS, which is used to treat intra-cranial and spinal targets. Treatment of extra-cranial sites, excluding the spinal cord and related spinal structures, requires accounting for internal organ motion as well as for patient motion. Thus, reliable immobilization or repositioning systems must often be combined with devices capable of decreasing organ motion or accounting for organ motion, e.g., respiratory gating. Additionally, all SBRT is performed with at least 1 form of image guidance to confirm proper patient positioning and tumor localization prior to delivery of each fraction.

SBRT may be delivered in 1 to 5 sessions (fractions). Each fraction requires an identical degree of precision, localization and image guidance. Since the goal of SBRT is to intensify the potency of the radiotherapy by completing an entire course of treatment within an extremely accelerated time frame, any course of radiation treatment extending beyond 5 fractions is not considered SBRT.

Inverse treatment planning is used for IMRT/SRS/SBRT and involves multiple steps 1,2,3 :

• For SRS procedures, position stabilization would be needed via a patient affixed frame or a stereotactic mask fixation system (frameless).

• Imaging: 3D image acquisition of the target area by simulation using computed tomography (CT), magnetic resonance (MR), positron emission tomography (PET) or similar image fusion technology is done. Usually, CT images will serve as the baseline image set for dose calculations. With IMRT or SBRT, when respiratory or organ motion is expected during radiation delivery, multi-phasic treatment planning imaging sets might also be done.

• Contouring: This is done in multiple steps and defines the target and avoidance. The radiation oncologist reviews the 3D images and outlines the treatment target on each image slice. The sum of these contours equals the gross tumor volume (GTV). If SRS is being planned, the neurosurgeon may also be involved in the contouring process. Next, a margin may also be drawn around the GTV (if no previous surgical treatment has occurred) to also include areas at risk for microscopic disease. This is the clinical target volume (CTV). And then, to account for daily patient set-up variation and motion issues, a final may be added to create a planning target volume (PTV). Any combination of these volumes may be contoured depending on the clinical scenario and treatment intent. Proximate normal structures that could be harmed (OARs) must also be contoured.

• Prescription: The radiation oncologist prescribes specific radiation doses. Usually, a prescribed dose must be given to at least 90-95% of the PTV. There is often a dose constraint describing an acceptable range of dose homogeneity. Dose constraints for the OARs should be present as an upper limit of mean dose and/or a maximum allowable point dose and/or a critical volume of the OAR that must not receive a dose above a certain limit. Prescribed doses to targets and OARs should maximize disease control and minimize radiation injury risk to normal tissue.

• Dosimetric Planning, Calculations and Verification: The physicist or supervised dosimetrist will calculate a multiple static beam and/or modulated arc treatment plan to deliver the prescribed radiation doses to the PTV and also meet OAR dose constraints. Dose volume histograms must be prepared for the PTV and OARs. Continuously moving MLCs are used to deliver the optimized modulated radiation doses to the tumor and nearby organs within that patient. The distinguishing feature of an IMRT plan is that it demonstrates how treatment with non-uniform beam intensities will be delivered. Basic dose calculations are done on each of the modulated beams or arcs in order to verify the computerized calculations. The calculated beams or arcs are delivered to a phantom or a dosimetry measuring device to confirm the intended dose will be accurate and that delivery will be technically feasible. For SRS, the quality assurance must be quite stringent to ensure dose delivery within 1 mm accuracy.

*** WHEN INVERSE TREATMENT PLANNING IS PERFORMED AND THAT PLAN IS UTILIZED, THE RADIATION ONCOLOGIST OR PHYSICIST MUST DOCUMENT THAT FACT. [Despite notations of optimization or use of certain computerized systems or other data, it is still necessary for the type of treatment planning either conventional forward planning or inverse planning to be specifically documented. C ollaboration with one’s electronic medical record vendor is strongly recommended to help support meeting this documentation requirement.]

Image-guided radiation therapy (IGRT) uses imaging to maximize accuracy and precision throughout the process of full treatment delivery, not just during treatment planning. It is particularly applicable to highly conformal treatment modalities, such as CRT and IMRT. With SBRT and SRS, IGRT is considered a necessary and integral component of the entire procedure. IGRT techniques might use onboard kilovoltage radiation imaging, cone beam CT scanning, MRI or ultrasound alone or in combination. This allows smaller margins to account for day-to-day differences in positioning of the patient. It is often used in conjunction with IMRT and other advanced forms of RT. IGRT would typically be used with tumors in areas that move such as the lungs, liver, pancreas, cervix and prostate. Marked obesity in conjunction with deep tumors in the abdomen, pelvis or mediastinum might require the help of IGRT. The medical necessity for the imaging modality and frequency must be assessed and documented for each patient. If applicable, the methods used to minimize organ motion should be documented.

COVERAGE GUIDANCE

This limited LCD pertains to various types of RT treatment approaches.

Indications and Limitations of Coverage and/or Medical Necessity

IMRT

IMRT is clinically indicated when highly conformal dose planning is required to spare normal surrounding tissue as a specific clinical benefit to that individual beneficiary.

Based on medical necessity, disease sites that may support the use of IMRT include the following:

• Primary, metastatic or benign tumors of the central nervous system (CNS) including the brain, the brain stem, and spinal cord

• Primary or metastatic tumors of the spine where the spinal cord tolerance may be exceeded with conventional treatment or where the spinal cord has previously been irradiated

• Primary, metastatic, benign or recurrent head and neck malignancies, with treatment directly impacting the orbits, paranasal sinuses, skull base, aero-digestive tract-nasopharynx, oropharynx, hypopharynx, and larynx/glottic areas, salivary glands, oral cavity, nasal cavity

• Thoracic malignancies

• Abdominal malignancies when dose constraints to small bowel or other normal abdominal tissue are exceeded

• Pelvic malignancies including: prostatic, gynecologic and anal carcinomas

• Other pelvic or retroperitoneal malignancies

• Reirradiation that meets the requirements for medical necessity and which is duly documented

Documentation of the medical necessity for each unique, individual beneficiary is crucial for allowing coverage and must include the following (please see the related billing and coding article for further detail):

• The specific diagnosis and target volume requiring IMRT; the total dose and dose per fraction

• The type of treatment planning used must be specified (i.e., forward or inverse)

• The specific prior history of any RT related to site and total dose

• A narrative statement documenting the special need for IMRT rather than conventional or 3D RT relating to the individual specific beneficiary

Medical necessity documentation for IMRT should include 1 or more of the following clinical scenarios:

• An immediately adjacent area has been previously irradiated and highly precise planning is needed for the current therapy with abutting portals

• Dose escalation is planned to deliver radiation doses exceeding those commonly used for similar tumors with conventional treatment

• The target volume is concave or convex, and the critical normal tissues are within or around that convexity or concavity

• The target volume is very close to critical structures that must be protected

• The volume of interest must be covered with narrow margins to adequately protect immediately adjacent structures

• With claimed delivery of prescribed IMRT, an easily identified, authenticated dose prescription must be present along with clearly labeled, color comparative treatment plans which include the dose volume histograms. Toward this requirement, collaboration with one’s electronic medical record vendor is strongly recommended.

Other malignancies not delineated above as potentially covered could be considered for coverage with submission of documentation for medical necessity should a denial occur. The determination of appropriateness and medical necessity for IMRT for any site shall be found in the documentation from the radiation oncologist and must be available when requested or submitted in the appeals process.

Limitations of Coverage:

IMRT is not considered reasonable and necessary when at least 1 of the above criteria relating to medical necessity are not documented as present.

Clinical scenarios that would not typically support the use of IMRT include:

• When conventional or CRT techniques can deliver good clinical outcomes and low toxicity

• In clinically urgent scenarios such as spinal cord compression, superior vena cava syndrome or airway obstruction

• For palliative treatment of metastatic disease where the prescribed dose does not approach normal tissue tolerances

• Inability to allow for organ motion, such as for a mobile lung tumor

• For a patient who cannot cooperate or who cannot tolerate immobilization to achieve accurate and reproducible delivery of doses

Non-Coverage

At this juncture, the following treatment is not considered reasonable and necessary due to insufficient evidence-based support:

• IMRT used in conjunction with proton beam RT 61

SRS

SRS may be considered medically reasonable and necessary for the following indications:

• Primary CNS malignancies, generally used as a boost or salvage therapy for lesions under 5 cm

• As a boost treatment for larger cranial or spinal lesions that have been treated initially with external beam RT or surgery (e.g., sarcomas, chondrosarcomas, chordomas, and nasopharyngeal or paranasal sinus malignancies)

• Primary and secondary tumors involving the brain parenchyma, meninges/dura, or immediately adjacent bony structures. For new brain metastases, the patient must have a documented Karnofsky Performance Status (KPS) score > 70% or an Eastern Cooperative Oncology Group (ECOG) status score of 0-2, be absent of leptomeningeal metastases, and not have a primary diagnosis of a lymphoma or germ cell tumor. For repeat brain metastases therapy, the patient must have a KPS score > 70% or ECOG of 0-2, no leptomeningeal metastases, stable extra-cranial disease on restaging studies done within the prior 2 months, and a life expectancy of > 6 months. (In the case of brain metastases, this contractor will not attempt to calculate the performance scale score based on information pieced together from the record; the numeric scale specific score and the life expectancy must be documented in the patient’s record. Please see the additional information below under Associated Information and Sources of Information for KPS and ECOG scoring information.)

• Benign brain tumors such as meningiomas, acoustic neuromas of Grade 3 or less, other schwannomas, pituitary adenomas, pineocytomas, craniopharyngiomas, glomus tumors, and hemangioblastomas

• Cranial arteriovenous malformations (AVMs) and cavernous malformations

• Trigeminal neuralgia, medically refractory epilepsy, severe Parkinson’s disease movement disorder, or severe and quality of life (QOL) impacting essential tremor that has not been responsive to medical management with at least 2 different agents at optimal doses. (The precise therapies, durations offered and responses to each therapy must be documented in the medical record.)

• Uveal or ocular melanoma

• Relapse in a previously irradiated cranial field where the additional stereotactic precision is required to avoid unacceptable vital tissue radiation

Limitations of Coverage:

SRS is not considered reasonable and necessary under the following clinical circumstances:

• When functional improvement is not expected

• When directed toward anything other than a severe symptom or serious threat to life or critical functions

• When clinically meaningful stabilization of the disease is not expected

• When other treatment could result in equally meaningful functional improvement or clinical stabilization

• Patients with poor performance status (KPS score 3)

• Patients with widespread cerebral or extra-cranial metastases with limited life expectancy

SBRT

SBRT may be considered medically reasonable and necessary for the following indications:

• Primary malignant tumors and tumors metastatic to the lung when the following criteria are met:

• Early stage primary tumors in medically inoperable patients, OR

• Recurrent early stage lung cancer in medically inoperable patients, OR

• Early stage primary tumors in high operative risk patients, OR

• Limited metastatic disease, good performance status, and the intention is eradicating all known active disease or greatly reducing the total disease burden in a manner that can extend progression-free survival (PFS).

• Primary tumors and tumors metastatic to the liver when the following criteria are met:

• Primary tumors when the patient is not a surgical candidate, OR

• Limited metastatic disease, good performance status, and the intention is eradicating all known active disease or greatly reducing the total disease burden in a manner that can extend PFS.

• Primary tumors and tumors metastatic to the kidney when the following criteria are met:

The evolution of IMRT technology has demonstrated improved clinical outcomes to the point that many disease sites need to be considered as potentially appropriate for this therapy. Professional society and national clinical guidelines create the foundation for this LCD’s limited coverage related to evidence-based RT approaches.

Sources for this coverage LCD, such as American Society for Therapeutic Radiology and Oncology (ASTRO) and National Comprehensive Cancer Network ® (NCCN ® ), have compiled many peer-reviewed publications which report clinical outcomes for these therapies related to cancer type and disease site. These publications have thus informed those credible specialty organization model policies and guidelines. In turn, these model policies and guidelines have all been reviewed for purposes of creating a foundation for this coverage LCD.

The ASTRO Model Policies for IMRT, SRS, and SBRT 1,2,3 address coverage and limitations based on a review of available literature.

IMRT Evidence Review