Almost all prostatic carcinomas (>70%) develop in the PZ and BHP (>90%) arises from the TZ ( McNeal)
Small tumors tend to occur in the anteromedial gland, adjacent to the fibromuscular stroma, whereas larger, more advanced T stage tumors are often located in the posterior gland near the prostatic capsule
Multifocality is characteristic of prostate cancer -77% ( Jewett )
TZ tumors - demonstrate a lower frequency of ECE and may harbor large volumes of disease with relatively high PSA levels but remain confined to the prostate. Despite a high PSA value (>10 ng/mL), considered to have a favorable prognosis
PZ cancers - spread along the capsular surface of the gland, and may extend through the capsule of the gland, invade seminal vesicles and periprostatic tissues, and involve the bladder neck or the rectum.
TRUS of the prostate, first described by Wantanabe (1968)
TRUS-guided systematic sextant biopsy protocol by Hodge
Normal adult prostate : Symmetric, triangular, relatively homogenous structure with an echogenic capsule
The mature average prostate is between 20 and 25 g and remains relatively constant until about age 50, when the gland enlarges in many men ( Griffiths, 1996 ) The paired seminal vesicles are positioned posteriorly at the base of the prostate. They have a smooth, saccular appearance and should be symmetrical. Normal SV measures 4.5 to 5.5 cm(l) and 2 cm (w)
Lacks the soft tissue resolution needed to detect intraprotatic anatomic changes due to primary tumor , capsular extension or SVI because the neoplasm usually has the same attenuation as the normal prostate gland
Can't detect microscopic disease
False Positive- Artifact of Bx and plane b/w SV and UB base may be obscured by rectal distension
Based on the degree of glandular differentiation and overall pattern of tumor growth
Adenocarcinoma- well/ mod./ poorly diff. according to the cellular characteristics i.e. nuclear content, no. of nuclei, pleomorphism, gland formation and stromal invasion
5 patterns of growth
Histologic variation in tumor, so two predominant patterns are recorded for each case
Primary/ predominant pattern (1-5)
Secondary / lesser pattern (1-5)
Sum of the 1º and 2º patterns (2-10)
>50% ca contain ≥2 patters
One of the strongest predictors of biological behaviour, invasiveness and metastatic potential
GLEASON GRADING It is important to recognize Gleason pattern 4 tumor because tumors with this pattern have a significantly worse prognosis than those with pure Gleason pattern 3 ( McNeal et al, 1990 ). Tumors with Gleason score 4 + 3 = 7 have a worse prognosis than those with Gleason score 3 + 4 = 7 ( Chan et al, 2000 ) GS Gleason’s Pattern Histo. Grade Differentiation 10 yr Progression (%) 2, 3, 4 1, 2 I Well <25 5, 6, 7 3 II Mod. 50 8, 9, 10 4, 5 III Poorly 75
PTV = CTV +a margin to account for physical uncertainties including setup reproducibility, inter- and intrafractional organ motion (1-cm margin added to the CTV to form the PTV in all directions except posteriorly at the interface with the rectum, where the margin is reduced to 0.6 cm)
Beam Selection and Planning
Standard 3D conformal beam arrangement- six coplanar fields, including two lateral, two anterior and two oblique beams
Conformal apertures drawn around the PTV adding a margin of ~5 to 6 mm in the axial directions to account for beam penumbra
Beam shaping, MLCs used
Dose distribution calculated for a few representative planes, typically transverse, coronal, and sagittal planes through the isocenter
DVH generated for the PTV, femoral heads, and rectum, bladder and bowel
6-field plan, the two lateral beams typically deliver ~1/2 of the dose to the isocenter with the four oblique beams contributing the rest. The beam weights of the anterior oblique and posterior oblique beams adjusted to obtain a uniform dose within the PTV and to place the hot spots away from the rectum
The plan normalized so that the prescription isodose (100%) covers the PTV
Radiation beam intensity or ‘Fluence’ varies across the fields
Delivery of an IMRT intensity pattern requires a computer-controlled beam-shaping apparatus on the linear accelerator known as MLC which consists of many small individually moving leaves or fingers that can create arbitrary beam shapes
Static mode - “STEP AND SHOOT” which consists of multiple small, irregularly shaped fields delivered in sequence
Dynamic mode - Dynamic multileaf collimation with the leaves moving during treatment to create the required irregular intensity patterns
Defining dose ‘Constraints’ or ‘Objectives’ for the target and normal tissues, which describe the desired dose distribution in IMRT planning
Constraints: Maximum or minimum dose limits on targets and dose-volume limits on normal tissues
Mathematical optimization of the radiation intensities of many small ‘beamlets’ within each treatment field which result in a set of intensity patterns for the treatment fields and a dose distribution with characteristics as close as possible to the constraints entered
Dose delivery carried out by setting each field to desired gantry angle with prescibed leaf position and MU
Isodose distribution- concave / convex
T/t verification with weekly portal films/ online portal imaging
Short course IMRT- 70 Gy/28#/5 1/2 weeks @ 2.5Gy/#
Low risk- 70-75 Gy Intermediate and high risk- 75-80 Gy
Volume study- TRUS imaging is obtained before the planned procedure to assess the prostate volume ( Holm et al )
Seed selection- isotopes/ loose or stranded/activity
Treatment planning- A computerized plan is generated from the transverse ultrasound images, producing isodose distributions and the ideal location of seeds(at 1 cm interval) within the gland to deliver the prescription dose to the prostate
SCREENING GUIDELINES FOR THE EARLY DETECTION OF PROSTATE CANCER (AMERICAN CANCER SOCIETY)
PSA test and DRE should be offered annually,
Beginning at age 50, to men who have a life expectancy of at least 10 years.
Men at high risk (African-American men and men with a strong F/H of one or more first-degree relatives diagnosed with prostate cancer at an early age) should begin testing at age 45.
For men at average risk and high risk, information should be provided about what is known and what is uncertain about the benefits and limitations of early detection and treatment of prostate cancer so that they can make an informed decision about testing.
Very high : T3b-T4 <10yr >10yr Expectant m/m or RT or RP±PLND RP±PLND or RT Androgen ablation or RT+Androgen ablation Any T, N1 Any T, Any N, M1 Androgen ablation Androgen ablation or RT+Androgen ablation Relapse risk Expected survival Initial T/t LOW : T1, T2a GS 2-6 PSA< 10 <10yr Intermediate : T2b, T2c GS 7 PSA-10-20 Expectant m/m or RT or RP±PLND High : T3a GS 8-10 PSA>20 >10yr Expectant m/m or RT Androgen ablation +RT or RT or RP±PLND
Most widely used system devised for the USA-based Veterans’ Administration Co-operative Urological Research Group (VACURG)
Grade 1: well-differentiated carcinoma with uniform gland pattern.
Grade 2: well-differentiated carcinoma with glands varying in size and shape.
Grade 3: moderately differentiated carcinoma with either (a) irregular acinae often widely separated; or (b) well-defined papillary/cribriform structures. This is the commonest pattern seen in carcinoma of the prostate.
Grade 4: poorly differentiated carcinoma with fused glands widely infiltrating the prostatic stroma. Neoplastic cells may grow in cords or sheets and the cytoplasm is clear.
Grade 5: very poorly differentiated carcinoma with no or minimal gland formation. Tumour cell masses may have central necrosis.