The name Mantle technique comes from the word „mantle‟ which is a type of cloak. It has been named so because the areas included in this radiation field technique resembles a person wearing a cloak. It has been used traditionally for the treatment of Hodgkins lymphoma.
• It is a type of Extended field radiation techniqueand includes multiple involved and uninvolvedlymph node groups.• When the multiple sites are involved above thediaphragm then the field used is known asMantle Field.
• Mantle field is used for Supradiaphragmaticfield.• It includes the following group of lymphnodes: • Bilateral Cervical • Bilateral Supraclavicular • Bilateral Infraclavicular • Bilateral Axillary • Bilateral Hilar • Bilateral Mediastinal
In the earlier days, before the advent of effective chemotherapy, radiation alone was used for the treatment of HL. This meant use of large radiation fields as well as raising the radiation dose to normal tissue limits. It was associated with late development of many complications and increased mortality of cured patients beyond what was expected of normal population.
With the advent of effective and less toxic chemotherapy drugs, the use of RT alone in HL has now got a limited role. In several types of HL now, chemotherapy alone has become the primary modality of treatment with RT used for consolidation and reduction of risk of relapse.
CLASSIFICATION OF RISK GROUPS FOR HL STAGE I/II STAGE III/IV EARLY ADVANCEDFAVOURABLE UNFAVOURABLE FAVOURABLE UNFAVOURABLE
Early Favorable :Clinical stage I/II without any risk factorsEarly Unfavorable :Clinical stage I/II with one or more of the following riskfactors : 1. Large mediastinal mass 2. Extra nodal involvement 3. Involvement of >=3 LN areas 4. High ESR (>30mm/hr for B stage; >50mm/hr for A stage) 5. B symptoms
Advanced Favorable :Clinical stage III/IV with 0-3 risk factorsAdvanced Unfavorable :Clinical stage III/IV with >=4 risk factorsRisk factors1. Male sex2. Age 45 yrs or more3. Hb < 10.5 gm%4. Albumin < 4.0 gm/dL5. Stage IV disease6. WBC count >= 15,000/mm37. Absolute lymphocyte count <600/mm3 or lymphocyte count <8% of total WBC count
CHEMOTHERAPY DRUGS USED FOR HL1. MOPP regimen : Mechlorethamine, vincristine (oncovin), procarbazine, prednisolone. Had high risks of sterility and secondary malignancies (leukemia, lung cancer).2. ABVD regimen : Adriamycin, bleomycin, vinblastine, dacarbazine. This regimen is much better tolerated by patients and the risks that were associated with the MOPP regimen are very less in this regimen.
• The patient is placed supine with maximumextension of the neck and arms above the head, orat 90* angle towards the side, or in „akimbo‟position, i.e., hands on the waist.
• In the arms above the head position, the axillarynodes were brought further away from the chest.This helped in a more generous lung shielding.• In the „akimbo‟ position, the humeral heads canbe shielded and also it minimized the effect oftissue folds in supraclavicular/low neck regions.
• Neck should be in maximum extension to exclude the oral cavity and teeth from the RT field and to decrease the dose to the mandible. CORRECT• All palpable lymph nodes should be markedwith wires.
BORDERSSuperior : Through the chin, bisecting themandible, to the mastoid process.Lateral : Flashing the axillaeInferior : Inferior axillary at the inferior tip ofscapula. Inferior mediastinal at the initialmediastinal extent of the disease with a ~ 5 cmsmargin ( T10-T11 interspace ).
SHIELDINGLung blocks : Made separate for anterior and posterior.Upper border in anterior : 2 cms below medial clavicle, and a thinlung band is left at the lateral clavicles.Upper border in posterior : a thin band is left under the clavicles asthe infraclavicular LN‟s are located anteriorly.Lateral Borders : a 1 cm band is left in costal curves which extendsuntil the 5th or 6th costa and finishes horizontally in chest wall.Medial Border : bilateral mediastinal and hilar lymphatics areincluded (mediastinal enlargement should be included).
• Head of Humerus is shielded both anteriorly andposteriorly.• Larynx is shielded anteriorly.• Heart is shielded below the hilar level withoutincluding the mediastinal LN‟s both anteriorly andposteriorly.• Spinal cord shielding is done in midline for dosages >40Gy.• A small block is put at the inferior border of spinal cordposteriorly.• Oral cavity is shielded if the superior border includesthe oral cavity.
• The central axis of the field is usually at the sternalnotch or close to it.• The central axis, points 10 cms left and right of it, andthe inferior border, should be marked with a tattoo tocheck during the daily setup and to allow thepossibility of infradiaphragmatic RT at later stages.
Beams : Parallel opposed SSD : at 100-120 cms (Extended SSD) Field Size : 40 x 40 cm2 Dosage : 36 - 40 Gy (Standard dose at Stanford was 44 Gy)
MINI MANTLE : Hilar and Mediastinal lymph nodes are not included. MODIFIED MANTLE : Axillary lymph nodes are not included.
ACUTE : Fatigue Radiation dermatitis in the areas of irradiated skin. Mouth dryness Pharyngitis
EARLY : Lhermitte‟s Sign : Electric-shock like sensation radiating down the back of both legs when the head is flexed. Seen in ~<5% patients within 6 weeks to 3 months after Mantle field RT. Resolves spontaneously within few months with no late/permanent spinal cord damage. Pneumonitis Pericarditis
LATE : Hypothyriodism Secondary Malignancies : High incidents of patients treated by mantle field RT to develop secondary solid tumors – most commonly lung and breast. Coronary Artery disease
LARGE FIELD EXTENDED SSD INHOMOGENOUS DOSE DISTRIBUTIONIRREGULAR BLOCKS AND SHIELDS SLANTING BODY CONTOURS
LARGE FIELD EXTENDED SSD (40 X 40 cm2) (100 – 120 cms)• A change in the SSD leads to a change in thePercentage Dose Depth (PDD) and the beam output.• Mayneord Factor is used to determine the PDD forthe extended SSD.
IRREGULAR BLOCKS SLANTING BODY AND SHIELDS CONTOURS IRREGULAR FIELD• The irregular fields which are produced arecorrected by using Clarkson‟s Method for irregularfield dose calculation.
• Due to the inhomogeneous dose distribution, theminimum dosimetry should include an irregular fieldpoint calculation for each important nodal region in thefield.• The dose variations determined by these calculationsmust be compensated by individually designedcompensators or selective area blocking.
IFRT (Involved Field Radiation Therapy) This is limited to the site of the clinically involved lymph node group. For extra nodal sites, the field includes the organ alone (if there is no evidence of lymph node involvement). The “grouping” of lymph nodes is not clearly defined.
ILRT (Involved Lymph node field RT) This is the latest radiation field which has been introduced for the treatment of HL. The clinical target volume (CTV) includes only the originally involved lymph node(s) volume (pre-chemotherapy) with the addition of 1cm margin to create a planning target volume (PTV).
The Mantle Field used earlier for irradiating supradiaphragmatic HL had many drawbacks : the field size involved was too large with an extended SSD. the demarcation of the proper target field with the proper sheidings was a very difficult and time consuming task to perform the dose calculation for the involved field was also a very troublesome task with lots of calculations involved. the late complications, especially that of secondary solid tumors, was a major cause of morbidity and mortality after the primary HL had been treated.
The newer modalities of Radiation therapy like IFRT and ILRT (used in combination with chemotherapy) use smaller fields and the treatment planning and simulation, dose calculation and complications associated with them are much less than what was seen with Extended field techniques like Mantle Field. Also, as they are used in conjugation with chemotherapy, so the dose can be reduced from 40 Gy to 30 Gy. The use of chemotherapy drugs has helped in limiting the use of RT in cases of Hodgkin‟s Lymphoma, and combined modality of treatment is more effective and less toxic than radical radiation alone.