radio - oncology 2008

VICTOR Q. ALABASTRO, MD, FPCR, FUSP, FPROS, FPSO

Historical Perspective: Early Observations of the effects of Ionizing

Radiation1895 - x-rays discovered by Roentgen1896 - first skin burns reported

- first use of x-ray in the treatment of cancer - discovery of radioactivity of Becquerel

1897 – first case of skin damage reported1899 – first basal cell epithelioma reported cured1902 – first report of x-ray induced cancer1911 – first report of leukemia in human and lung

cancer form occupational exposure1911- 94 cases of tumor reported in Germany ( 50 being

radiologist)

MODALITIES TRADITIONALLY USED IN THE MANAGEMENT OF PATIENTS WITH CANCER

A. SURGERY – for lesions that can be technically removed completelyLimitations are:

1. inadequate removal of the gross tumor, leading to a local recurrence

2. inadequate resection of microextensions in tissues adjacent to gross tumor.

3. undetected metastasis to regional lymph nodes

4. systemic micrometastases


B. RADIATION THERAPHY – for localized lesions in which surgery may cause anatomically or physiologically undesirable sequelae and for more extensive lesions not amenable to a surgical resectionLimitations are: I. Tumor cell burden

a. inadequate depopulation of clonogens in the primary tumor which may cause local recurrence

b. regional microextensions or metastasis to lymphatics which may not be included in the irradiated volume may cause a recurrence

c. clinically unapparent distant metastasis at the time of initial therapy


II. Physical and technical factorsa. inaccurate tumor localization because of the oncologist inability to define the target volume adequately( geographic miss )b. inadequate treatment planning, which may result in non-homogenous doses of radiation throughout the target volumec. unreliable daily irradiation techniques, which may result in poor positioning and immobilization (inaccurate treatment)


III. Biologic factors

a. Hypoxic cell subpopulation which require higher doses of radiation than well oxygenated cells for the same level of cell kill

b. Repair of sublethal or potentially lethal damage after irradiation

c. Position of the cell in the proliferative cycle. Cells in the late G1 or S phase are more resistant to irradiation than are cells in other portions of the cycle. Cells in the G0 are also more resistant to irradiation than are rapidly proliferating cells


d. Tumor cell repopulation during fractionated therapy or after completion of therapy

e. Limited tolerance of the surrounding normal tissues to irradiation, thus precluding the delivery of higher doses

3. CHEMOTHERAPY – used in several settings

ADJUVANT – to eradicate microscopic metastases or tumor cell dissemination outside the operated or irradiated volume


NEOADJUVANT – to reduce the initial tumor cell number before definitive surgery or irradiation or both and potentially to decrease the viability of micrometastases

DEFINITIVE THERAPY – in tumors that are chemosensitive and can be controlled with cytotoxic agents alone

PALLIATIVE – in the treatment of systemic macrometastases or to relieve symptoms in patients with chemosensitive tumors


Limitations are:I. Pharmacodynamics factors:

a. decreased drug diffusions because of abnormal vasculature in the tumor

b. decreased drug incorporation and use in the cellII. Biologic factors

a. Tumor cell burden – chemotherapy is more effective against a smaller number of tumor cells

b. Proportions of clonogenic cells – cytotoxic agents are more effective in proliferating cells and less efficacious in cell with low proliferative activity


II. Biologic factorsc. Variation of cell sensitivity to drugs throughout the proliferative cell cycle. Some drugs are phase specific ( killing or arresting dividing cells during specific phase of cell cycle such as DNA synthesis), cycle specific (killing proliferating cell more effectively than resting cells) or nonspecific ( equally toxic for resting cycling cellsd. Chemoresistance – some cells that initially respond to chemotherapy may later be affected less or not at all by the same drug or combinations, even at a higher dose


II. Biologic factorse. mode of administration and timing of administration of one drug in relation to the other, may allow for tumor cell synchronization or sensitization of the tumor cell to the effects of other drugsf. Dose of chemotherapy and frequency of administration – the frequency of administration or higher doses of chemotherapy have a substantial impact on the induction and maintenance of tumor regression

COMBINATION OF THERAPEUTIC MODALITIES

IRRADIATION AND SURGERY

The following tumors are indications for combined surgery and radiation therapy:1. tumors with low cure rates by either surgery or radiation therapy alone2. tumor with great potential for local or regional recurrence3. tumor with great potential for residual disease after surgery4. tumors with great potential for lymphatic invasion5. for preservation of function and the enhancement of cosmesis

RATIONALE FOR PREOPERATIVE RADIATION THERAPY

1. Its potential ability to eradicate subclinical disease beyond the margins of the surgical resection

2. To diminish tumor implantation by decreasing the number of viable cells within the operative field

3. To sterilize lymph node metastases outside the operative field

4. To decrease the potential for dissemination of clonogenic tumor cells that might produce distant metastases

5. To increase the possibility of resectability

DISADVANTAGE OF PREOPERATIVE IRRADIATION

- It may interfere with normal healing of tissues affected by the radiation. ( interference is minimal if radiation doses are below 4500 cGy to 5000 cGy in 5 weeks)

RATIONALE FOR POSTOPERATIVE RADIATION

- Based on the facts that it is possible to treat any residual tumor in the operative field by:

a. destroying subclinical foci of tumor cells following the surgical procedure

b. by eradicating adjacent subclinical foci or cancer ( including lymph node metastases)

c. by delivering higher doses than can be achieved with preoperative irradiation – the greater dose being directed to the volume of high risk or known residual disease.

Disadvantage:- related to the delay imposed on the initiation of radiation therapy until wound healing is complete - vascular changes produce in tumor bed by surgery may impair radiation effect

IRRADIATION AND CHEMOTHERAPY

- The effects of combined radiation therapy and chemotherapy can be described as independent, additive or interactive

- Administration of chemotherapy before radiation therapy produces some cell kill and reduction in the number of cells to be eliminated by the irradiation

- use of chemotherapy during radiation therapy has a strong rationale because it could interact with the local treatment ( additive and even supra-additive action) and could also affect subclinical disease early in treatment

- Chemotherapy after radiation therapy as an adjuvant has been used primarily for control of subclinical disease

INTEGRATED MULTIMODALITY CANCER MANAGEMENT

- Combination of two or even all modalities frequently are used to improve tumor control and patient survival

- Steel postulated the biologic basis of cancer therapy as :a. spatial cooperation – in which an agent is active against tumor cells spatially missed by another agentb. addition of anti-tumor effects by two or more agentsc. non-overlapping toxicity and protection of normal tissues

RADIATION ONCOLOGY- a clinical and scientific endeavor

devoted to:a. management of patients with cancer ( and other disease) by ionizing radiation, alone or combined with other modalitiesb. investigation of the biologic and physical basis of radiation therapyc. training of professionals in the field

RADIATION THERAPY- a clinical specialty dealing with the use of

ionizing radiation in the treatment of patients with malignant neaplasia ( and occasionally benign conditions)

- Often use in combination with chemotherapy and surgery

- Its goal is to deliver with accuracy a precisely measured dose of radiation to a defined tumor volume with as minimal damage as possible to surrounding healthy tissue resulting in eradication of the tumor, a high quality of life and prolongation of survival at a reasonable cost

- it is generally assumed that 50-60 % of cancer patients will benefit from radiotherapy

MAJOR INDICATIONS FOR RADIOTHERAPY

1. Head and neck cancers2. Gynecological cancers ( eg. Cervix)3. Prostate CA4. Other pelvic malignancies ( rectum, bladder)5. Adjuvant breast treatment6. Brain Cancer7. Palliation

TREATMENT APPROACHES IN RADIOTHERAPY

1. CURATIVE TREATMENT – to obtain complete durable remission; it is projected that the patients has an expected probability of surviving after adequate therapy even if that chance is lowa. radiotherapy is the sole agent with curative intent for anatomically limited tumors of the retina, optic nerve, brain, spinal cord, nasopharynx, etc.b. radiotherapy is combined with surgery for more extensive cancers of the head and neck, lungs, breast, testis, etc.c. radiotherapy is an adjuvant to chemotherapy for some patients with lymphomas, lung cancer and cancer in children


2. PROPHYLACTIC TREATMENT – this consists of irradiation of macrocospically uninvolved areas which are thought to be the site of occult subclinical localizations

a. radiotherapy to the regional, clinically uninvolved lymphatic chains after surgery and/or radiotherapy to the primary tumor.

b. radiotherapy to the lymphatic chains, the spleen and the brain in the absence of clinically evident lesions in malignant lymphomas


2. PROPHYLACTIC TREATMENTc. radiotherapy after macroscopically radical surgery for locally advanced cancers at a high risk of local relapsed. radiotherapy to the brain when the primary cancer has a high risk of spreading to the brain (eg. Small cell lung CA )

3. PALLIATIVE TREATMENT – limited intent of improving the patient’s quality of life and prolonging his survivala. allow for a symptom-free period appreciably longer than the debilitation cause by the irradiation treatment period


3. PALLIATIVE TREATMENT

b. prolong useful or comfortable survival so that other factors might lead to death

c. relieve distressing symptoms although survival may not be prolonged

d. avert impending symptoms such as hemorrhage, perforation, obstruction etc.

RATIONALE OF RADIATION THERAPY IN METASTATIC DISEASE

1. Relieve severe pain

2. Control hemorrhage

3. Prevent impending pathologic fracture

4. Reverse spinal cord compression before transection takes place

5. Alleviate superior vena cava syndrome

6. Relieve symptoms and disability from brain metastases

7. Prevent obstruction

8. Halt destruction of an organ

A COMPARISON OF MAIN MODALITIES OF RADIOTHERAPY

BRACHYTHERAPY- Administration of radiation

therapy by applying a radioactive material inside the patient or in close approximation to the patient

- Dose outside the treatment volume can be minimized

- Inside the treatment volume, the dose is necessarily non-uniform and dose gradients are often high

- Normally limited to accessible sites, either near the surface of the body or near natural cavities but any volume may be treated using complex array of sources

- Dose rates are usually relatively low

TELETHERAPY- Delivery of radiation treatment

to the patient from a machine located remote from the body

- Dose outside the treatment volume will in general be greater than in brachytherapy

- Any required degree of dose uniformity can in principle be achieved inside the treatment volume

- No physical limitations to the size of volume that can be treated

- Dose rates are usually relatively high

TYPES OF TELETHERAPY

1. Conventional Roentgen Therapy – consist of the use of x-rays produced by equipment functioning with voltages up to 400 kv

a. short distance roentgen therapy – 3-5 cm using voltages form 50-60 Kv

b. middle distance roentgen therapy – 15-30 cm using voltages greater than 100 Kv

c. deep roentgen therapy – uses voltages from 250-400 Kv

TYPES OF TELETHERAPY

2. External Radiotherapy with high energy photons – most commonly used method for irradiation of deep and semi-deep seated tumors

a. Cobalt 60 teletherapy unit

b. linear accelerators

3. External Radiotherapy with fast electrons

a. Betatrons – up to 45 Mev

b. Linac – up to 25 Mev

TYPE OF EQUIPMENTS AND THEIR ENERGY RANGE

1. Superficial x-ray10 Kv – Grenz Ray40-140 Kv – superficial

2. Orthovoltage250 Kv – Deep X-ray; 600 Kv – Radioisotope Teletherapy ( Cs-137)

3. Supervoltage or Megavoltage2 Mev – Radioisotope Teletherapy ( Co-60)4-6 MV – low energy Linear accelerator18-20 MV – high energy Linear accelerator15-25 MV – dual mode Linear accelerator

AVANTAGES OF TELECOBALT UNITS AND MEGAVOLTAGE

GENERATORS OVER ORTHOVOLTAGE

1. Better depth doses – more efficient tumor treatment

2. Less side effects – less radiation sickness

3. No differential absorption by bone – more uniform dosage

4. Skin sparing effects – only skin radiation dermatitis

ELECTRONS BEAMS CAN BE USED IN THE PRINCIPAL TREATMENT OF THE FF:

1. Malignant tumors of the skin and lip

2. Chest wall, neck and brain cancers ( used electrically after radical or conservative surgery or with recurrent disease)

3. Upper respiratory or digestive tract lesion form 1cm to 5cm in depth

4. Lymph nodes, operative scars and residual tumor

TYPES OF BRACHYTHERAPY1. Interstitial Brachytherapy – this consist of the

introduction of variously shaped radioactive sources ( needle, wire, seeds) into the tissue at or near the tumor site. It is used to treat tumors of head and neck, prostate, cervix, ovary, breast, perianal and pelvic region

2. Endocavitary Brachytherapy – this consist of the introduction of radioactive sources contained in “applicators” or in molded devices inside natural, pathological or operative cavities. It is commoly used to treat uterine cancer; researchers also used this for breast, bronchial, cervical, gallbladder, oral, rectal, tracheal, uterine and vaginal cancers

TYPES OF BRACHYTHERAPY

3. Contact Brachytherapy – this consist of the application through direct contact to the skin surface or other sites ( cornea, external mucous membrane) of radioactive sources ( usually beta-emitting) for the treatment of very superficial neoplasms

TELETHERAPY SOURCES

UNIT

150-440 Kvp xrayCesium 137 Cobalt 60 4 MV Linac6 MV Linac

20-24 MV Betatron and Linac

MEAN ENERGY PHOTONS(MeV)

0.06-0.140.661.251.31.8

6.2-7.0

BRACHYTHERAPY SOURCES

Half Life Effective Energy

(Mev)

Radium 226 1620yrs 1.2Cesium 137 30 yrs 0.66Iridium 192 74days 0.34Iodine 125 60day 0.027Gold 198 2.7 days 0.41

THE EFFECTS OF RADIATION ON THE BODY DEPENDS ON:

1. The volume of tissue irradiated2. The anatomical site irradiated3. The radiation dose delivered4. The rate at which the radiation is

delivered5. Dose fractionation

IRRADIATION FRACTIONATION REGIMEN

1. Conventional fractionation – consist of daily fractions of 1.8 to 2.0 Gy 5 days a week; total dose is determined by type of tumor and tolerance of critical normal tissues.( usually 60 to 75 Gy)

2. Hyperfractionation – uses increased total dose, numbers of fractions is increased, dose per fraction is reduced and overall time is unchanged.

3. Quasi – hyperfractionation – same as hyperfractionation except that total dose is not increased.

4. Accelerated fractionation – overall time is reduced, the number of fractions, total dose and dose per fractions are unchanged or reduced.

5. Quasi – accelerated hyperfractionation – same as accelerated fractionation except the overall time is not reduced because of treatment interruptions

Radiological factor Mechanism of effect on response

Clinical relevance

Radiosensitivity Intrinsic radiosensitivity differs between cells of tumors and normal tissue types, and strongly determines final surviving fractions

Can account for variable response of tumors.Curative dose is proportional to the log of cell number (so subclinical disease needs smaller dose)

Repair Cells differ in their capacity to repair DNA damage, particularly after small doses of radiation.Repair is usually more effective in non-proliferating cells. The repair process takes at least 6 h to complete

Repair is maximal in late-responding tissues given small fractions. Hyperfractionation may be advantageous . Treatments need to be well separated in order to avoid compromising repair.


Clinical relevance

Repopulation Surviving cells in many tumors and in acute-responding (but not in late-responding) normal tissues proliferate more rapidly once treatment is in progress

Shortened treatment times (accelerated therapy) may be advantageous for some tumors. Acute (but not late) effects will be increased. Gaps should be avoided

Reoxygenation Hypoxic cells, which occur especially in tumors, are relatively resistant to radiation. Hypoxic surviving cells reoxygenate, becoming radiosensitive, as treatment proceeds

Very short treatment times could lead to resistance due to persistence of hypoxic cells


Clinical relevance

Redistribution Cells in certain phases of the proliferative cycle (e.g. late S) are relatively resistant and survive preferentially. With time between fractions, cells redistribute themselves over all phases of the cycle

Closely spaced treatment fractions could lead to resistance due to persistence of cells in less sensitive phases

TREATMENT PLANNINGOBJECTIVE: To achieve a dose distribution inside the

volume to be treated(target volume) which is uniform within ±5% of the prescribed dose while limiting the dose to adjacent regions to below tolerance levels

1. Tumor localization and assessment of volume of tissue to be irradiated

2. Choice of radiation quality and selection of treatment machine

3. Selection of radiation dose and dose-time relationship4. Selection of radiation field arrangement and any

necessary beam shaping devices5. Calculation of radiation dose distribution and daily

treatment time6. Manufacture and use of devices to ensure accurate

localization of treatment field and accurate and easily reproducible set-up from day to day

7. Preparation of radiotherapy prescription

THE PRESCRIPTION OF RADIATION IS BASED ON THE FOLLOWING PRINCIPLES

1. Evaluation of the full extent of the tumor (staging) by whatever means available including radiographic, radioisotope and other studies

2. Knowledge of the pathologic characteristic of the disease including potential areas of spread that may influence choice of therapy ( that is the rationale for elective irradiation of the lymphatics in the neck or the pelvis)

3. Definition of goals of therapy (cure vs palliation)4. Selection of appropriate treatment modalities

which may be irradiation alone or combined with surgery, chemotherapy or both

THE PRESCRIPTION OF RADIATION IS BASED ON THE FOLLOWING PRINCIPLES

5. Determination of the optimal dose of radiation and the volume to be treated which is made according to the anatomic location, histologic type, stage and other characteristics of the tumor and the normal structures present in the region

6. Periodic evaluation of the patients general condition, tumor response and status of the normal tissues treated

CURATIVE DOSES OF RADIATION FOR DIFFERENT TUMOR TYPES

2000-3000 cGySeminomaDysgerminomaAcute Lymphocytic Leukemia3000-4000 cGySeminoma (bulky)Wilm’s tumorNeuroblastoma4000-4500 cGyHodgkin’s diseaseLymphosarcomaHistiocytic cell sarcomaSkin Cancer( basal cell)


5000-6000 cGy

Lymph nodes, metastatic (No,N1)

Squamous Cell CA, cervix CA, head and neck CA

Embryonal CA, Ewing tumor, Breast CA (excised)

Breast CA, Ovarian CA, Medulloblastoma, Retinoblatoma

6000-6500 cGy

Larynx (< 1cm)

Breast cancer( T1)


7000-7500 cGy

Oral cavity ( <2cm, 2-4cm)

Oro-naso-laryngo-pharyngeal CA

Breast CA(T2), Bladder CA, Cervix CA, Uterine fundal CA

Ovarian CA, Lymph nodes, metastatic (1-3cm),

Lung CA (<3cm)

8000 cGy or above

Head and Neck CA (>4cm), Breasts CA (>5cm), Glioblastoma, Osteogenic sarcoma, Melanomas, Soft tissue sarcomas(>5cm), Thyroid CA, Lymph nodes, metastatic (>6cm)

RESPONSE TO TREATMENT1. Complete remission – no clinically detectable

cancer is formed following treatment2. Partial remission – measurable tumor is

decreased by 50% following treatment; no new area of cancer can be found and no area of tumor shows progression

3. Minimal remission – same as partial remission but not meeting the criteria of 50% reduction

4. Progression – increased of tumor mass by more than 25%; appearance of new lesions or tumor-induced death

5. Stable disease – measurable tumor does not meet the criteria for CR, PR, MR, or progression

CAUSES OF FAILURE IN RADIATION THERAPY

1. Error of judgment eg. – wrong diagnosis – wrong treatment

- failure to detect metastasis before exposing the patient to radical treatment for the primary tumor

2. Error of Omissioneg. – failure to give an adequate level of dosage

3. Error of Commissioneg. – habitual use of a poor technique will in time be reflected in a lower cure rate than might have been expected

- error in dose calculation- badly positioned xray applicator which

can lead to the so called “ geographic miss” with an inevitable result of failure to control growth

POSSIBLE SPECIFIC SEQUELAE OF THERAPY

ANATOMIC SITE ACUTE SEQUELAE LATE SEQUELAE

BRAIN Earache, headache, dizziness, hair loss, erythema

Hearing loss, damage to middle or inner ear, pitiutary gland dysfunction, cataract formation, brain necrosis

HEAD AND NECK Odynophagia, dysphagia, hoarseness, xerostomia dysgeusia, weight loss

Subcutaneous fibrosis, skin ulceration, necrosis, thyroid dysfunction, persistent hoarseness, dysphonia, xerostomia, dysgeusia, cartilage necrosis, osteoradionecrosis of mandible, delayed wound healing, fistula, dental decay, damage to middle &inner ear, apical pulmonary fibrosis rare: myelopathy

LUNGS AND MEDIASTINUM OR ESOPHAGUS

Odynophagia, dysphagia, hoarseness,cough, pneumonitis, carditis

Progressive fibrosis of lung, dyspnea, chronic cough, esophageal stricture, rare: chronic pericarditis,

myelopathy

BREAST OR CHEST WALL

Odynophagia, dysphagia, hoarseness, cough, pneumonitis, carditis, cytopenia

Fibrosis, retraction of breast, lung fibrosis, arm edema, chronic endocarditis, MI, rare:osteonecrosis of ribs

ABDOMEN OR PELVIS Nausea, vomiting, abd. pain, diarrhea, urinary frequency, dysuria, nocturia, cytopenia

Proctitis, sigmoiditis, rectal or sigmoid stricture, colonic perforation or obstruction, contracted bladder, urinary incontinence, hematuria due to chronic cystitis

Vesicovaginal fistula,rectovaginal fistula,leg edema, scrotal edema, sexual impotency,vaginal retraction,or scarring,sterilization,damage to liver or kidney

EXTREMITIES Erythema, dry/moist desquamation

Subcutaneous fibrosis, ankylosis, edema, bone/soft tissue necrosis

OTHER METHODS OF TREATMENTI. INTRAOPERATIVE RADIATION THERAPY

- a form of external radiation that is given during surgery- it is used to treat localized cancers that cannot be completely removed or that have a high risk of recurring in nearby tissues- one large high energy dose of radiation is aimed directly at the tumor site during surgery(nearby healthy tissue is protected with special shield- it is costly, time consuming procedure because of the necessity of combining the operating room’s sterile technique with the high energy equipment in a shielded room.- it may be used in the treatment of thyroid and colorectal cancers, gynecological, small intestinal and pancreatic cancers- its is also being studied in clinical trials to treat some types of brain tumor and pelvic sarcomas in adults

OTHER METHODS OF TREATMENT

II. STEREOTACTIC RADIOSURGERY

- uses a stereotactic frame, a radiation delivery system computer hardware and treatment planning hardware

- the patient head is placed in a special frame, which is attached to the patients skull. The frame is used to aim high-dose radiation beams directly at the tumor inside the brain

- it is often performed on outpatient basis and is a time consuming process involving the placement of the stereotactic frame determination of target size and location and treatment planning and treatment delivery

OTHER METHODS OF TREATMENTThis can be done in 3 ways:

1. Linac based stereotactic radiosurgery – uses a linear accelarator to administer high-energy photon radiation to the tumor

2. Gamma knife – uses Cobalt 60 to deliver radiation

3. Heavy charged particle beam therapy – uses protons and helium ions to deliver radiation

Indications: the presence of a suitable size( generally less than 4 cm) radiographically distinct lesion that has potential to respond to a single large dose of radiation

- the largest worldwide experience has been in to treatment of arteriovenous malformations

- Low grade and high grade gliomas- 2nd most common indication is primary or secondary

treatment of brain metastasis ( up to 3 brain metastases)- Middle fossa meningiomas- Acoustic neurinomas

STEREOTACTIC RADIOTHERAPY- Uses essentially the same approach as stereotactic

radiosurgery to deliver radiation to the target tissue- However, it uses multiple small fractions of radiation as

opposed to one large dose- Giving multiple smaller doses may improve outcome and

minimizes side effects- Is used to treat tumors in the brain as well as other part of

the body

III. TOTAL BODY IRRADIATION- has been used as a form of systemic therapy for various disease

Indications:1. a. patients with autoimmune disease - <2 Gy given as

single fractionb. allogenic bone marrow transplantation - >9.5 Gy if used alone to prevent graft rejectionc. patient with aplastic anemia for bone marrow transplantation – single dose of 3 Gy in conjunction with cyclosphosphamide to reduce the probability of graft rejection

2. Low-Dose Systemic Therapy for Chronic Lymphocytic Leukemia and Non-Hodgkins Lymphoma – 0.05 to 0.15 Gy 2x to 5x a week for leukocystosis

3. High-Dose Cytoreductive Therapy before bone marrow or Peripheral blood Stem Cell transplantation – 1.2 Gy 3x/day with partial lung blocks

HEMIBODY IRRADIATION (HBI)

- Was developed as a method to treat patients with disseminated tumors involving multiple sites

- Line passing across the bottom of L4 is commonly used to separate upper and lower HBI

- Most effective dose were: 6 Gy for upper HBI, 8 Gy for lower and middle HBI with 80% pain improvement in 1 week

- Comparing HBI added to local irradiation with local radiation therapy alone. Studies showed that adjuvant single dose HBI:a. delayed the progression of existing diseaseb. reduced the frequency of new diseasec. delayed as well as reduced the need for retreatment

NONSEALED RADIONUCLIDE THERAPY

- Use of radioactive materials which may be taken by mouth or injected into the body ( SYSTEMIC RADIATION THERAPY)

- Currently approved non-sealed radionuclide sources are:

1. Sodium iodine (131I)- treatment of hyperthyroidism ( diffuse toxic goiter, toxic multinodular goiter, solitary toxic thyroid nodule)

- definite adjuvant therapy and palliation of same thyroid carcinomas (papillary, follicular)

2. Sodium phosphate (32P)- treatmentj of myeloproliferative disorders such as polycythemia vera and thrombocytosis

NONSEALED RADIONUCLIDE THERAPY

3. Colloidal chromic phosphate (32P)- intracavitary therapy for malignant ascitis, malignant effusion, brain cysts

4. Samarium (153Sm)- palliation of painful bone metastases

5. Strontium chloride (89Sr)- palliation of painful bone metastases

OTHER METHODS TO IMPROVE EXTERNAL RADIATION THERAPY

I. THREE DIMENSIONAL CONFORMAL RADIATION THERAPY- uses computer technology to allow doctors to more precisely target a tumor with radiation beams (using width, height and depth)- A 3-D image of a tumor can be obtained using CT scan, MRI etc.- using information from the image, special computer programs design radiation beams that “conforms” to the shape of the tumor. Because the healthy tissue surrounding the tumor is largely spared by this technique, higher doses of radiation can be used to treat the tumor- improved outcomes have been reported for nasopharyngeal, prostate, lung, liver and brain cancers


II. INTENSITY MODULATED RADIATION THERAPY ( IMRT)

- A new type of 3-D conformal radiation therapy that uses radiation beams (usually X-rays) of varying intensities to deliver different doses of radiation to small areas of tissue at the same time

- The technology allows for the delivery of higher doses of radiation within the tumor and lower doses to nearby healthy tissue

- Some techniques deliver a higher dose of radiation to the patient each day potentially shortening the overall treatment and improving the success of treatment


II. INTENSITY MODULATED RADIATION THERAPY ( IMRT)

- The radiation is delivered by a linear accelarator that is equipped with a multileaf collimator ( a collimator that helps to shape or sculpt the beams of radiation)

- The equipment can be rotated around the patient so that radiation beams can be sent from the best angles

- This new technology has been used to treat tumors in the brain, head and neck, nasopharynx, breast, liver, prostate and uterus

FLOW CHART OF FUNCTIONS IN RADIATION THERAPY

Clinical evaluation and staging, e.g. TNM

Treatment intent: radical or palliative

Choice of treatment: surgery, radiotherapy, chemotherapy


Description of treatment

Method of patient immobilization

Image acquisition of tumor and patient data for planning

Delineation of volumes (GTV, CTV, PTV)

Choice of technique and beam modification

Computation of dose distribution


Dose prescription

Implementation of treatment

Verification

Monitoring treatment

Recording and reporting treatment

Evaluation of outcome

Squamous cell CA of the balanopreputial region with extension into the glands. Patient was treated with 120kVp xray, 0.3-mmCu half-

value layer, receiving skin dose of 6000 cGy in 5 weeks

Same patient 4 years later with no evidence of disease

Patient with a 4 cm epidermoid Ca in the labia and clitoris

Portal used to deliver external irradiation to treat the pelvis and vulvar areas to 5000 cGy. Bolus was used

over right inguinal areas

Posttreament photograph 3 years later shows excellent cosmetic results. Patient is tumor

free

Patient with squamous cell CA of the ear

External mould used with a high-dose rate remote control afterloading device.

Posttreatment photograph showing complete tumor-regression and satisfactory cosmetic results

Medial tangential portal

Lateral tangential portal

AMDG (ad majorem de glorium)

the end

radio - oncology 2008

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