Trina Lynd, M.S. Medical Physicist Lifefirst Imaging & Oncology Cullman, AL Tri-State Alabama, Louisiana and Mississippi Spring 2016 Meeting April

Transcription

1 Trina Lynd, M.S. Medical Physicist Lifefirst Imaging & Oncology Cullman, AL Tri-State Alabama, Louisiana and Mississippi Spring 2016 Meeting April 17, 2016

2 Discuss permanent prostate brachytherapy and its role in the treatment of prostate cancer Identify physics processes involved in the execution of a permanent prostate brachytherapy case Present useful resources, documents and reports to use as references

3 Prostate Cancer is the 2 nd most common cancer in American men, following skin cancer Prostate Cancer is the 2 nd leading cause of death in men, following lung cancer Statistics taken from American Cancer Society s website

4 Radical Prostatectomy External Beam Radiation Therapy Temporary & Permanent Brachytherapy Androgen Deprivation Therapy Watchful waiting or active surveillance Cryotherapy Vaccine treatment Bone directed treatment Taken from American Cancer Society s website

5 American Cancer Society s estimates for prostate cancer in ,890 new cases 26,120 deaths 1 of 7 men will be diagnosed with prostate cancer 6 of 10 men diagnosed will be > 65 1 of 39 men will die of prostate cancer Statistics taken from American Cancer Society s website

6 SURVIVAL FOR ALL STAGES 5 year almost 100% 10 year 98% 15 year 95% SURVIVAL BROKEN DOWN INTO DISEASE LOCATIONS Localized almost 100% Regional almost 100% Distant 28% Statistics taken from American Cancer Society s website

7 Low Risk: Gleason score < 6, PSA < 10ng/mL, tumor classification T 1 or T 2a Intermediate Risk: Gleason score 7 or PSA > 10 ng/ml<20ng/ml or T 2b, T 2c High risk: Gleason score 8-10 or PSA >20ng/mL or T 3a Seminal vesicle involvement T 3b high risk in evaluation and treatment

8 Permanent prostate brachytherapy is an outpatient procedure with rapid recovery and quick (within several days) return to normal activity. Historically prostate brachytherapy consisted of freehand placement of seeds in an open surgical procedure using retropubic approach. 2 Modern prostate brachytherapy utilizing Iodine-125 ( 125 I) with transrectal ultrasound (TRUS) & template pioneered around early 1980 s. 3

9 FAVORABLE INDICATORS 4 UNFAVORABLE INDICATORS 4 Life expectancy > 5-10years T 1b T 2c & some T 3 Gleason scores 2-10 PSA < 50 ng/ml No pathological lymph nodes No distant metastases Unsuitability for general anesthesia Severe urinary irritative/ obstructive symptoms Extensive TURP defect Large median lobe Large prostate size Pubic arch interference Gross Seminal Vesicle involvement Prior pelvic radiation Inflammatory bowel disease Pathologic involvement pelvic lymph nodes Metastatic disease

10 Table 4 from American Brachytherapy Society Consensus Guidelines for Transrectal Ultrasound Guided Permanent Prostate Brachytherapy, Brachytherapy 11 (2012)

11 Table 6 from American Brachytherapy Society Consensus Guidelines for Transrectal Ultrasound Guided Permanent Prostate Brachytherapy, Brachytherapy 11 (2012) 137 Cs was introduced in 2004 Historically 198 Au was used but not recommended at present time

12 125 I 103 Pd Monotherapy: 145 Gy Monotherapy: 125 Gy Boost: Gy with 41.4 Gy 50.4 Gy of External Beam Radiation Therapy Boost: Gy with 41.4 Gy 50.4 Gy of External Beam Radiation Therapy

13 125 I 103 Pd Air Kerma U or mci 2 RTOG clinical trials mCi 3 90% of dose delivered in 197 days 2 Air Kerma U or mci 2 RTOG clinical trials mci 3 90% of dose delivered in 56 days 2 American Brachytherapy Society does not recommend a seed activity or total activity 3

14 NOTE SEED ACTIVITY UNITS WHEN ENTERING INTO THE TREATMENT PLANNING COMPUTER! Air Kerma Strength Conversions 1 ugy m 2 /h (U) = mci for 125 I 1 ugy m 2 /h (U) = mci for 103 Pd 1 ugy m 2 /h (U) = mci for 137 Cs

15 LOOSE SEEDS Mick applicator uses seeds preloaded into a cartridge on site or by vendor Pre-loaded in needles on-site or by vendor STRANDED SEEDS Bard QUICKLINKED sources Amersham Rapid Strand TM

16 AAPM TG56 recommends 10% of seeds assayed prior to implantation Seeds can be assayed in bulk or mick cartridges A single calibrated seed from same batch can be sent with seeds which are sent in preloaded needles, sutured/sterile strands Autoradiographs

17 Seeds need to be sterilized before loading Loose seeds can be loaded into Mick cartridges and then sterilized Sterilization methods: Autoclave Flash sterilization Steam sterilization Ethylene oxide gas required for seeds in sutures

18 American Brachytherapy Society acknowledges that the nature of permanent prostate brachytherapy precludes exact precision in final seed placement and consequently a wide range of post plan variability is not only accepted but expected 3

19 Preplan prior to scheduled OR case Patient positioning must be reproducible in OR Treatment plan generated to determine: # of needles Needle locations on template # of seeds Strength of seeds

20 Transrectal ultrasound images preferred method for imaging, MRI acceptable Image 2-3 weeks prior to case to limit changes in prostate volume Axial images 5mm intervals from base to apex Check for public arch inference

21 Transrectal ultrasound 3D images acquired in OR under anesthesia Patient in same position throughout whole procedure Adjustments can be made to optimize positioning rectum and pubic arch Acquire images at 5mm intervals Nomogram table used to double check planning parameters

22 Contour prostate, bladder, rectum, urethra, seminal vesicles with patient in actual treatment position Create treatment plan while patient is prepped Obtain assistance and approval from Radiation Oncologist immediately Guide and monitor placement of needles and seeds with ultrasound Monitor migration of seeds Monitor swelling of prostate

23 Uniform loading 1 cm apart center-to-center requires higher seed count using decreased strength Modified peripheral loading some seeds deleted from center to decrease central dose Peripheral loading seed limited to periphery requiring higher seed strength

24 General or spinal anesthesia Dorsal lithotomy position with elevation of legs in stirrups with upper thighs at right angle Rectum cleaned out, hopefully with enema prior Alignment of ultrasound probe with prostate and rectum Posterior edge of prostate needs to be in close proximity to last row on template Good visualization of urethra

25 Transrectal Ultrasound Imaging favored for preplanning and intraoperative planning Ultrasound with longitudinal and sagittal views provides visualization of prostate base and apex Verify perineal template grid and electronic grid coincide Easy visualization of rectum Urethra can be visualized most of time with catheter in place. Aerated gel placed into catheter improves visualization tremendously

26 AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer: Report of AAPM Task Group 137

27 MRI good imaging tool for preplanning and post planning Soft tissues easily visualized MRI can be merged with ultrasound and CT to improve target delineation MRI is not as commonly used as other modalities for permanent prostate brachytherapy

28 AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer: Report of AAPM Task Group 137

29 AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer: Report of AAPM Task Group 137

30 CT commonly used for post implant planning Delineating the prostate is extremely difficult particularly with seeds in place CT prostate volumes tend to be overestimated which result in lower plan doses CT on Day 0 or 1 convenient for patient, early detection of problems

31 Post implant edema large factor in post implant evaluations Edema is most apparent the days immediately following procedure Edema can be as great as 40-50% ABS recommendations for timing of post planning CT is dependent upon radionuclide used 125 I 30±7 days 103 Pd 16±4 days

32 Development of D 90 concept by Stock and peers Minimum dose received by the hottest 90% of the prostate volume, also described as isodose line enclosing 90% of prostate. 3 Many studies have shown that D 90 and V 100 are correlated with outcomes 3

33 AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer: Report of AAPM Task Group 137

34 So many parameters being followed ABS postoperative dosimetry recommendations 3 D 90 expressed in Gy and % V 100 expressed in % V 150 expressed in % UV 150 expressed in volume UV 5 expressed in % UV 30 expressed in % RV 100 expressed in cc

35 Image based volumetric plan CT, MRI, ultrasound or a combination Slice thickness 5mm 3D isodose planning DVH analysis

36 1. American Cancer Society website 2. Permanent prostate seed implant brachytherapy: Report of American Association of Physicist in Medicine Task Group No American Brachytherapy Society consensus guidelines for transrectal ultrasound guided permanent prostate brachytherapy, Brachytherapy 11(2012) 4. Dosimetry of interstitial brachytherapy sources. Recommendations of the AAPM Radiation Therapy Committee Task Group No Code of practice for brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task Group No AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer: Report of AAPM Task Group 137