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Radiotherapy (RT) is an integral component in the treatment of prostate cancer. Intensity-modulated radiotherapy (IMRT) has been proposed as a method of RT that allows adequate RT to the tumor while minimizing the radiation dose to surrounding normal tissues and structures.
For prostate cancer, RT is one accepted option for treatment. Other treatment options include surgery, hormonal treatment, and watchful waiting.
Conventional external beam radiotherapy. Over the past several decades, methods to plan and deliver RT have evolved in ways that permit more precise targeting of tumors with complex geometries. Most early trials used 2-dimensional treatment planning based on flat images, and radiation beams with cross-sections of uniform intensity that were sequentially aimed at the tumor along 2 or 3 intersecting axes. Collectively, these methods are termed conventional external beam radiotherapy (EBRT).
Three-dimensional conformal radiation. Treatment planning first evolved by using 3-dimensional images, usually from computed tomography (CT) scans, to delineate the boundaries of the tumor and discriminate tumor tissue from adjacent normal tissue and nearby organs at risk for radiation damage. Computer algorithms were developed to estimate cumulative radiation dose delivered to each volume of interest by summing the contribution from each shaped beam. Methods also were developed to position the patient and the radiation portal reproducibly for each fraction, and immobilize the patient, thus maintaining consistent beam axes across treatment sessions. Collectively, these methods are termed 3-dimensional conformal radiotherapy (3D-CRT).
Intensity-modulated radiotherapy. IMRT, which uses computer software and CT and magnetic resonance imaging images, offers better conformality than 3D-CRT, as it is able to modulate the intensity of the overlapping radiation beams projected on the target and to use multiple-shaped treatment fields. It uses a device (a multileaf collimator [MLC]) which, coupled to a computer algorithm, allows for “inverse” treatment planning. The radiation oncologist delineates the target on each slice of a CT scan and specifies the target’s prescribed radiation dose, acceptable limits of dose heterogeneity within the target volume, adjacent normal tissue volumes to avoid, and acceptable dose limits within the normal tissues. Based on these parameters and a digitally-reconstructed radiographic image of the tumor and surrounding tissues and organs at risk, computer software optimizes the location, shape, and intensities of the beam’s ports, to achieve the treatment plan’s goals.
Increased conformality may permit escalated tumor doses without increasing normal tissue toxicity and thus improve local tumor control, with decreased exposure to surrounding normal tissues, potentially reducing acute and late radiation toxicities. Better dose homogeneity within the target may also improve local tumor control by avoiding underdosing within the tumor and may decrease toxicity by avoiding overdosing.
Because most tumors move as patients breathe, dosimetry with stationary targets may not accurately reflect doses delivered within target volumes and adjacent tissues in patients. Furthermore, treatment planning and delivery are more complex, time-consuming, and labor-intensive for IMRT than for 3D-CRT. Thus, clinical studies must test whether IMRT improves tumor control or reduces acute and late toxicities when compared with 3D-CRT.
Methodologic Issues in IMRT research
Multiple-dose planning studies have generated 3D-CRT and IMRT treatment plans from the same scans, then compared predicted dose distributions within the target and in adjacent organs at risk. Results of such planning studies show that IMRT improves on 3D-CRT with respect to conformality to, and dose homogeneity within, the target. Dosimetry using stationary targets generally confirms these predictions. Thus, radiation oncologists hypothesized that IMRT may improve treatment outcomes compared with those of 3D-CRT. However, these types of studies offer indirect evidence on treatment benefit from IMRT, and it is difficult to relate results of dosing studies to actual effects on health outcomes.
Comparative studies of radiation-induced side effects from IMRT versus alternative radiation delivery are probably the most important type of evidence in establishing the benefit of IMRT. Such studies would answer the question of whether the theoretic benefit of IMRT in sparing normal tissue translates into real health outcomes. Single-arm series of IMRT can give some insights into the potential for benefit, particularly if an adverse effect that is expected to occur at high rates is shown to decrease by a large amount. Studies of treatment benefit are also important to establish that IMRT is at least as good as other types of delivery, but in the absence of such comparative trials, it is likely that benefit from IMRT is at least as good as with other types of delivery.
Note: IMRT of the breast and lung is considered separately in another policy
Intensity-modulated radiotherapy (IMRT) may be considered medically necessary in the treatment of localized prostate cancer at radiation doses of 75 to 80 Gy.
IMRT is considered investigational for the treatment of prostate cancer when the above criteria are not met.
Localized prostate cancer is defined as cancer confined to the prostate, or locally advanced cancer that is confined to adjacent structures and/or local lymph nodes. For localized prostate cancer, IMRT may offer advantages in both local tumor control and reducing toxicity to adjacent normal tissues. For nonlocalized prostate cancer, it is uncertain whether this is the case and radiation to the prostate is not usually given as part of treatment.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
POLICY HISTORY1/19/2009: Policy added
5/15/09: Policy reviewed, no changes
12/28/2009: Added prior Approval for FEP members effective January 1, 2010.
07/16/2010: Policy Exceptions section revised to state that as of July 1, 2010, prior approval is no longer required for outpatient IMRT provided for the treatment of prostate cancer for FEP members.
08/17/2010: Added CPT code 77338 to the Covered Codes table.
04/26/2012: Policy reviewed; no changes.
08/09/2013: Policy reviewed; no changes.
07/18/2014: Policy title changed from "Intensity-Modulated Radiation Therapy (IMRT) of the Prostate" to "Intensity-Modulated Radiotherapy of the Prostate." Policy description updated. Medically necessary policy statement revised to change "radiation therapy" to "radiotherapy." Added policy statement: IMRT is considered investigational for the treatment of prostate cancer when the above criteria are not met. Policy guidelines updated regarding localized prostate cancer.
SOURCE(S)Blue Cross Blue Shield Association policy # 8.01.47
CODE REFERENCEThis may not be a comprehensive list of procedure codes applicable to this policy.
The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.