Breast site external radiation therapy.pptx

Breast RT

1. Radiotherapy Planning in Breast Presenter: Haripriya Moderator: Dr. Elna Jerod

2. Indications TREATMENT VOLUME INDICATION COMMENT Whole breast Routinely following BCS Consider omission RT in elderly with stage I disease, favourable molecular profile and comorbidities Boost Routinely following whole breast irradiation No boost for widely negative margins in women over 60

3. TREATMENT VOLUME INDICATION COMMENT Supraclavicular -Clinical N2 or N3 disease ->4 positive LN after axillary dissection -1-3 positive LN with high risk features -Node + sentinel lymph node with no dissection unless risk of additional axillary disease is very small -High risk no dissection May omit with 1-3 positive nodes in selected cases Indications High risk features: - n odal involvement > 10-15% LVSI + Young female High histological grade

4. TREATMENT VOLUME INDICATION COMMENT Axilla -Node positive with extensive ECE -SN+ with no dissection -Inadequate axillary dissection -High risk with no dissection Axilla may be intentionally included with use of high tangents Internal mammary -Positive axillary nodes -Central and medial lesions with high risk -Stage III breast cancer -+ SLN in IM chain -+SLN in axilla with drainage to IM on lymphosintigraphy Indications High risk features: - n odal involvement > 10-15% LVSI + Young female High histological grade

5. Steps in Planning Counselling Consent Pre planning Audit CT Simulation – DIBH Training Target volume Treatment planning Dose & Fractionation Set up verification

6. Counselling Explain the procedure to the patient Check wound healing & need for seroma aspiration Check for any new signs / symptoms of local recurrence, particularly where RT has been delayed by more than 4 weeks To check chemotherapy & hormonal therapy schedule and document the last date of chemotherapy Confirm the target volumes to be treated High risk consent should be taken in case of possible high skin toxicities due to skin folds To note down the cosmesis in all post BCS patients

7. SIMULATION Patient Position Immobilisation Laser alignment DIBH CT Imaging

8. Patient Position Most important - Patient is comfortable - Reproducible Supine Prone Lateral Erect Older Techniques

9. Positioning Devices i. Breast Board

10. ii . Prone board : I/l breast gravitates through the hole in breast board Patient lies on stomach & rests arms over head C/l breast pushed away against an angles platform to avoid the radiation beam Includes: prone board, face cushion, 15 degree wedge, handles Advantages : heart & lungs are effectively eliminated in the treatment

11. SUPINE POSITION PRONE POSITION ADVANTAGES: Easy set up Narrowing of breast shape makes gaining a homogenous dose easier Most commonly used OARs can be separated from breast tissue leading to reductions in lung volume Can match nodal fields to CW fields when required Respiration in prone is limited – reducing intrafractional movement DISADVANTAGES: Gravity effect on large pendulous breast – loss of skin sparing inferiorly - Subsequent cosmesis PTV often doesn’t include CW which may be a problem depending on the position of original tumor Not possible to match nodal fields Difficult for patients to climb – risk of rib fractures Accuracy is not as good as supine position

12. Immobilization Devices Thermoplastic shells Adhesive tapes Vac lock Alpha cradle Breast ring L shaped breast plate

13. Deep Inspiration Breath Hold Heart - Inferior and postero -medial movement Two major methods: Active breathing control device (ABC)- regulation of inspiratory volumes It uses Spirometer to monitor airflow and stop it at set volume – causing patient to hold breath 2. Voluntary DIBH - verified by surface anatomy verification or direct volume measurement

14. Voluntary DIBH Table mounting camera Marker block Trained to t ake a deep breath and hold breath for 20 to 30 seconds Reproducible state of maximum breath - hold is advantageous

15. Free Breathing Breath holding Two scans are taken: One with free breathing- for reference for treatment setup Another in deep breath hold position

16. Dose to heart & lung by tangential fields Amount of lung included in the irradiated volume is greatly influenced by the portals used i . CLD ii. MLD iii. MHD

17. CLD : Central Lung Distance Predictor of percentage of ipsilateral lung volume treated by tangential fields Perpendicular distance from posterior tangential field edge to the posterior part of anterior chest wall at the center of field

18. Upto 2 – 3cm of underlying lung may be safely included in the tangential portals CLD % of lung irradiated 1.5cm 6% 2.5cm 16% 3.5cm 26% Radiation pneumonitis Risks CLD<3cm - <2% CLD 4-4.5cm - 10%

19. MLD : Maximum perpendicular distance from the posterior tangential field edge to the posterior part of anterior chest wall MHD : Maximum Heart Distance- Maximum perpendicular distance from posterior tangential field edge to heart borders

20. Cardiac toxicity More in left sided breast cancer patients Events include: - Pericarditis - Pericardial fibrosis - CAD - Diffuse myocardial fibrosis >30Gy exposure results in cardiac complications

21. Dose to heart can be minimized by: Cardiac block Prone positioning Breath hold Respiratory Gating methods Gating

22. Simulation Scar and entire breast is identified with wires / markers Field border is marked with radio-opaque wires CT scan extent : Superiorly from mastoid to upper abdomen ( upto L2/ covering entire liver) inferiorly Slice thickness based on institutional protocol (3-5mm for 3DCRT & 2.5mm for IMRT) Two reference tattoos are placed on the central slice

23. Patient position : Supine Arms abducted (> / = 90 degree), externally rotated & head turned to opposite side (only if SCF is treated) Breast tilt boards with arm rests used for positioning Head turned to opposite side- to spare mandible from SCF field

24. Head position: Rigid head holder or neck rest – to stablise & position head Chin should be elevated to minimize neck skin folds within SCF fields

25. Borders : Cranial : 2 nd ICS or head of clavicle, depending on SCF treatment Medial : at or 1cm away from midline Lateral : 2cm beyond all palpable breast tissue- mid axillary line Lower : 2cm below inframammary fold (of opposite breast if post MRM) Posteriorly: 1-3cm of lung Borders can be modified : - to cover entire breast tissue - include nodal volumes & scar

26. TREATMENT PLANNING Conventional Planning 3 dimensional Conformal Radiotherapy (3DCRT) Intensity Modulated Radiation Therapy (IMRT)

27. After BCS After Mastectomy Whole breast + Lumpectomy cavity boost (TBB) +/- Regional LNs Chest Wall OR Mastectomy scar Partial Breast Regional nodes Treatment Volumes

28. Conventional Planning Two tangential fields are used Additional fields may be required for SCF, IMN, boosting of axilla

29. Treatment Volume Entire breast + chest wall Upper margin – head of clavicle Medial margin – at / 1cm over midline (if no IMN) Medial tangential portal is located at lateral margin of internal mammary field (if IMN present) Lateral posterior margin – 2cm beyond all palpable breast tissue (mid axillary line) Inferior margin – 2-3cm below infra mammary fold

30. SCF Field Single anterior field is used Cranial border- Thyrocricoid groove Medial border- At or 1 cm across midline extending upward along medial border of SCM to thyrocricoid groove Lateral border- Just medial to humeral head, insertion of deltoid muscle Caudal - Matched with the cranial border of tangents Field is angled at approx 10-15 degree laterally to spare cervical spine Dose is calculated at the depth of 3cm

31. Axillary node irradiation Level I & II- included in tangent Level III- covered in SCF Modifications in tangential & SCF field can be done to cover axillary nodes Posterior axillary boost can be considered

32. Internal mammary irradiation Two techniques : Wide or deep tangents Direct anterior field matched to tangential fields

33. Wide Tangents The nodes in 1 st three ICS are considered most clinically significant Medial border of tangential field is moved 3-5cm across the midline to cover IMNs To minimize lung and cardiac exposure, block can be used

34. Separate IMN Field Medial – Midline Lateral - 5-6 cm from midline Superior – Inferior border of SCF (or lower border of clavicle) Inferior – At xiphoid (or higher if 1 st three ICS covered) Depth : 4-5cm

35. Accessories used Breast Cone Wedges

36. Breast Cone It is a beam modifying and directing device used in tangential radiotherapy The breast cone is designed to eliminate beam divergence and penumbra for the breast tangential portals.  The breast cone consists of a support plate and lead block to shield the contralateral side. 

37. Wedges Used as compensators in breast RT Dose uniformity within the breast tissue can be improved Preferred in lateral tangential field rather than medial tangential field Wedges can be compensated only along one axis Ideal wedge correction – small hotspot Overcorrection – Cold spots

38. Disadvantages of 2D planning Beam matching can be difficult Dosimetry is performed only in midplane of the target volume Dose distribution can be inhomogenous away from central axis ( Superoinferiorly ), especially in large breast Doses to OARs cannot be determined accurately Shielding of heart while treating the left breast wont ensure whether a part of target volume is being missed

39. Conformal Radiotherapy Standard opposed tangential fields with appropriate use of wedges and field in field technique to optimize dose homogeneity 3DCRT may improve dose to target volume & reduction in dose to normal tissues Better cosmetic results Less dose to heart and lung

40. Treatment Planning process: •Imaging – Computed Tomography •Image segmentation •Beam aperture design •Field multiplicity and collimation •Plan optimization and evaluation

41. Image Segmentation Slice by slice delineation of anatomic regions of interest: •Breast/ CW •Regional Lymph nodes •Critical normal structures

42. RTOG Consensus definition for anatomical boundaries CRANIAL CAUDAL ANTERIOR POSTERIOR LATERAL MEDIAL BREAST Clinical reference + 2 nd rib insertion Clinical reference + loss of CT apparent breast Skin Excludes pectoralis muscles, chest wall muscles, ribs Clinical reference + mid axillary line typically, excludes LD muscle Sternal rib junction

43. CRANIAL CAUDAL ANTERIOR POSTERIOR LATERAL MEDIAL BREAST + CW Same Same Skin Includes pectoralis muscles, chest wall muscles, ribs Same Same CHEST WALL Caudal border of the clavical head Clinical reference + loss of CT contralateral breast Skin Rib-pleural interface (Includes pectoralis muscles, chest wall muscles, ribs) Clinical reference / mid axillary line typically, excludes LD muscle Sternal rib junction

44. CRANIAL CAUDAL ANTERIOR POSTERIOR LATERAL MEDIAL Supraclavicular Caudal to cricoid cartilage Junc of BCV-axillary veins / caudal edge of clavicle head SCM ms Anterior aspect of scalene ms Cranial : lateral edge of SCM Caudal : junc 1 st rib-clavicle Excludes thyroid & trachea

45. CRANIAL CAUDAL ANTERIOR POSTERIOR LATERAL MEDIAL Axillary level I Axillary vessels cross lateral edge of Pect minor m Pect major ms insert into ribs Plane defined by ant surface of pect maj ms & LD ms Anterior surface of subscapularis ms Medial border of LD ms Lateral border of Pect minor ms Axillary level II Axillary vessels cross medial edge of Pect minor m Axillary vessels cross lateral edge of Pect minor m Anterior surface of Pect minor ms Ribs & Intercostal ms Lateral border of Pect minor ms Medial border of Pect minor ms Axillary level III Pect minor m insert on cricoid Axillary vessels cross medial edge of Pect minor m Posterior surface of Pect major ms Ribs & Intercostal ms Medial border of Pect minor ms Thoracic inlet

46. CRANIAL CAUDAL ANTERIOR POSTERIOR LATERAL MEDIAL IM N Superior aspect of medial 1 st rib Cranial aspect of 4 th rib

47. Beam aperture design • Beam direction • Beam aperture 95% isodose coverage of PTV is ensured Single isocenter

48. Field multiplicity & collimation • Multiplicity of fields removes need of ultrahigh energy beams (>10MV) • Field in field is used • Dynamic MLCs – to shape the beam • Independent jaws- half beam blocks

49. Field in Field • Provides more conformal dose by shaping the radiation beam and modulating high dose regions • This is Forward planned 3D/IMRT • Additional subfields are added to block specific hotspots in original tangential fields • Number of subfields is based on reducing maximum isodose volumes by 3% per field down to a goal of 107% of prescription dose

50. Half beam block technique By moving one of the independent jaws to midline, a half beam can be created This forms a non divergent field edge centrally The half beam block is easier to setup (less movements of gantry & couch)

51. Beam Modifying Devices Blocks Wedges Compensators Bolus Irregularities in chest wall contours Varying thickness of underlying lung

52. Bolus It increased dose to skin & scar after mastectomy In Post mastectomy RT, 0.5-1cm bolus is used over the CW every day Cosmetic results may be inferior Increases acute skin toxicities Universal wax bolus is used

53. Wedges

54. Alignment of tangential beams with CW contour Due to obliquity of anterior CW – tangential fields include disproportionate amount of lung cranio-caudally Breast board Rotating collimators MLC shaping

55. Rotating collimators Collimator of tangential may be rotated to resolve this The need of collimation can be eliminated if the upper torso is elevated so as to make CW horizontal

56. In collimated field, junction between bitangentials and SCF field results in hotspot / cold spots Need of collimation can be eliminated if the upper torso is elevated This is done by breast board

57. SCF & Axilla • Third Antero-posterior field is required for SCF • Angled 10-20 degrees – to avoid Spinal cord & esophagus • Inferior border should be non divergent to avoid overlap with tangents – Independent collimator jaws or Half beam blocks • Single Isocenter Technique- at the junction of two fields

58. If depth of Axillary nodes >5cm : • High energy photons (>6MV) • Anterior-medial or posterior-lateral beam arrangements • Additional posterior-anterior supplement beam (Posterior axillary boost)

59. IMN Different methods of IMN inclusion: • Wide tangents or partially wide tangents • Separate IMN field • IMRT Inverse planned IMN treatment

60. Wide tangents • Medial border is extended over the opposite breast/CW- to cover ipsilateral IMN •Wide tangents split inferiorly with a cardiac block and computer optimized wedge angles to minimise heart and lung dose – partially wide tangents

61. Boost to tumor site after Whole breast RT in BCS Local recurrences tend to be primarily in and around primary tumor site Boost decreases risk of marginal recurrence Given by: EBRT – electron / photon

62. Electron boost Electron beam boost is preferred because: Relative ease in setup Low dose to whole breast Good cosmetic results Lower cost Decrease time demands on physician Lumpectomy cavity + 2cm margins in all directions – approx. size of boost field Energy : Depth in cm * 3

63. Photon boost Mini tangent fields used to boost target volume Done in deep seated cavity

64. Treatment Setup CT dataset is used to create digitally reconstructed radiographs (DRRs) for orthogonal setup films & beams eye view for each tangential treatment field Port films & KV images are performed before delivering first treatment to confirm isocenter location & patient position Imaging frequency depends – daily setup variability, pt position, utilization of respiratory gating

65. Dose of Radiation Conventional dose : 46-50Gy in 23-25 fractions over 5 weeks (5 days/week) Hypofractionation : 40-42Gy in 15-16 fractions over 3 weeks (5 days/week) 40.05Gy in 15 fractions over 3 weeks Boost irradiation to tumor bed : 10-16Gy in 5-8 fractions over 1-1.5 weeks 12.5Gy in 5 fractions over 1 week Regional node irradiation : Same dose as whole breast / chest wall

66. OAR Ipsilateral Lung V30 Gy </= 17% Heart V25 Gy V5 Gy </= 5% </= 25% Contralateral Breast V3 Gy V5 Gy < 10% (preferred) < 10% (acceptable) OAR Constraints

67. Thank You