Mark L. Merlin, M.D.Radiotherapy Clinics of Georgia

7/14/2010

The Role of Radiation Therapy in the Management of Prostate

Cancer

• Radiation oncology is a field of medicine that specializes in the destruction of cancer cells using various forms of radiation– Balance normal tissue damage versus eradication

of cancer

• Radiation therapy works by either directly killing cancer cells or by damaging their DNA

• Normal tissue cells have a mechanism for repairing DNA damage

• Cancer cells have a diminished ability to repair this sub lethal damage

Natural history

• If detected early, prostate cancer remains confined to the prostate or immediately adjacent tissues– Spread to surrounding

nerves / fatty tissues– Spread to adjacent lymph

nodes– Spread to distant sites such

as bone

Radiation versus Surgery• Data is retrospective• Patient selection varies• Overall data does not suggest one option is better than

another• Some clinical situations may benefit more from one type of

therapy• Side effects vary significantly• Patients should research all options• Focus on cure rates, side effects, and quality of life issues• Centers of excellence

Radiation therapy options

• External beam therapy with photons - IMRT (Intensity Modulated Radiation Therapy)

• Brachytherapy– Permanent or temporary seeds

• Brachytherapy / External beam therapy• Particle therapy– Protons, Neutrons

• Stereotactic radiation– Cyberknife, Tomotherapy

External beam therapy

• Multiple photon beams aimed at a target• Patient specific moving shields for normal

tissues• IMRT – software planning based on CT scan

images• Daily treatment

External beam therapy• Photons enter through skin and are directed

at target• Some exposure to surrounding tissue• Improved imaging and computer software

Brachytherapy

• Radiation source is placed inside or next to the area requiring treatment

• Needles are placed through skin of the perineum• Radioactive seeds are implanted through needles• Permanent seeds – Iodine, Palladium, Cesium• Temporary seeds – Iridium

Brachytherapy

• Best used alone if the chance for extracapsular spread is low

• Chance for extracapsular spread relies on certain clinical factors:– PSA– Gleason score– Number of positive biopsies– Stage (findings on digital rectal exam)– Presence of perineural invasion

Brachytherapy combined with External Beam therapy

• Allows more intense radiation dose to prostate through brachytherapy

• Allows treatment with external radiation to encompass some areas around prostate for potential spread

• Combination may overcome limits of either modality on its own

Stereotactic Radiation

• Focused radiation beams targeting a well defined tumor using extremely detailed imaging scans– Cyberknife– Tomotherapy

• Cure rate data following treatment is not available

due to short follow-up

Particle therapy

• Special case of external beam radiation where the particles are protons or heavier ions

• Dose increases while the particle penetrates the tissue up to a maximum that occurs near the end of the particle’s range

• The dose then drops to almost zero

Proton beam therapy Loma Linda 2004 article

1255 pts treated with protons for prostate cancer Overall cure rate 73%

Massachusetts General 2008 article Recommended further study on protocol before rapid

adoption Cited tremendous increase in price for machines with no

proven benefit over current linear accelerators Protocols for dose, treatment setup, and parameters for

shielding uninvolved tissues remain in evolution Standard long term radiation effects on urinary and rectal

function do exist

Hormone therapy combined with radiation

• Two large randomized studies have shown that patients with locally advanced prostate cancer treated with standard external beam therapy have higher cure rates if they also receive testosterone suppression

• EORTC (2002) – GS 8-10 and T1/T2 or any T3/T4 pts– RT alone vs RT + LHRH x 3 yrs– 5 yr OS 62% vs 78%

• RTOG (2005) – T3 or N1– RT alone vs. RT + LHRH x 28 months– 10 yr absol surv 39% vs. 49%

Hormone therapy side effects

• Hot flashes• Decrease in muscle tone• Weight gain• Impotence• Decreased libido• Fatigue• Emotional lability• Increased risk of cardiovascular death• Breast enlargement / tenderness

Radiation following radical prostatectomy

• Following surgical removal of the prostate, a careful pathological analysis is done

• Organ confined vs. not confined (seminal vesicle involvement, capsule penetration, or margin involvement)

• Patients with certain features have a higher risk of cancer recurrence within the prostate bed

Radiation following radical prostatectomy

• In the past, many patients and physicians have followed the PSA level after surgery

• Recent randomized trials suggest that those patients with high-risk features should be evaluated for immediate radiation to the prostate bed

• Improved survival rates have been found with immediate vs. delayed radiation– 10 yr OS 71% vs. 61%

• Standard of care is to evaluate all high risk patients following surgery for possible radiation therapy

Radiation side effects

• Acute effects (during treatment)– Urinary– Rectal– General

• Late effects (months – years after treatment)– Urinary / Sexual– Rectal– Secondary Cancer

Get educated!

• Do your own research• Talk with friends and family• Use the internet• Get second opinions• Read prostate books

literature

• Organizations such as The Prostate Net help to raise public awareness and promote education of available resources

• Evidence based medicine• Centers of excellence with database of prior

patients

Any Questions?

Contact Information

Mark L. Merlin, M.D.Radiation Oncologist

Phone: 404-633-5606 Ext. 180 Email: mmerlin@rccancercenters.com