What is Radiation Therapy and what does it do?
Radiation Therapy (RT) is use of high energy Ionization radiation (often X Rays ) to kill a cancer cell by damaging its DNA. Goal of Radiation Therapy (RT) is to use focused beams of radiation to kill cancer cell with as little risk as possible to normal cells. Radiation treatment, like surgery, is a local treatment. It affects the cancer cells only in a specific area of the body.
Timing of RT-
RT can be used before surgery to shrink a tumor, called as neoadjuvant/pre operative RT (Pre op RT). It may be used after surgery to stop growth of cancer cells that may remain called as adjuvant RT (Post op RT). At times radiation is used alone with curative intent which is called as Radical RT. It can also be used at the time of surgery known as Intra-operative Radiation (IORT).
Types of RT
When the source of radiation is from a machine outside the body, it’s called as External Beam Radiation therapy (EBRT). When radioactive material is placed close to tumour or area harboring cancer cells it’s called as Brachytherapy.
What is EBRT?
EBRT is usually given during outpatient visits (OPD Treatment) to a hospital. In this, a machine (also called as Linear Accelerator/LA) directs the high energy rays at the tumor bearing area within body. The type of machine used for radiation therapy is called as a Linear Accelerator and at Max Hospital it has several models like True Beam STx, Novalis or Clinax. Linear Accelerators have the capability of delivering RT by various techniques like IMRT (Intensity Modulated Radiation Therapy), IGRT (Image Guided Radiation Therapy), SRS (Stereotactic Radiation Therapy) and SBRT (Stereotactic Body Radiation Therapy).
What is IMRT?
Intensity-modulated radiation therapy (IMRT) refers to a technique of focusing radiation therapy at cancer bearing area using computer based optimization process to carefully create a gradient or a dose fall-off between the cancer/target tissues and the surrounding normal tissues. This fall of dose saves the surrounding normal organs effectively. Therefore, these techniques offer the prospect of increasing the cancer control probability while decreasing the side effects.
What is IGRT?
Image guided radiation therapy (IGRT) is classically defined as radiation therapy that is delivered only after verification of position of structures of interest by performing either an X-Ray or CT based image. The same are done by an imaging system mounted on the linear accelerator itself. IGRT technically includes IMRT and hence also called as IM- IGRT (Intensity-modulated Image guided radiation therapy)
What is SBRT?
Stereotactic body radiation therapy (SBRT) refers to use of principles of stereotaxy to identify and pin pointedly deliver precisely deliver intense doses of RT to only to cancer/tumour area. SBRT is essentially similar to Stereotactic Radiosurgery (SRS) brain except that term SBRT used when we are targeting areas outside brain. Since SBRT involves delivery of higher intensity of radiation doses in shorter time, it also known as SABR (Stereotactic Ablative RT). SBRT is generally done by combining IMRT and IGRT together. SBRT generally has fewer sitting /fractions of radiation as compared to conventional IMRT or IGRT.
Your Radiation Oncologist will discuss all these techniques and how they are relevant for your cancer and its treatment.
What is more important for successful radiation therapy- Machine or team behind machine?
Both machines and team behind machines are equally critical in successful delivery of RT. We are fortunate that at MICC, we have this critical combination of the modern state of the art machines and a trained team available across all hubs of Max Hospitals.
True beam STX is an advanced radiotherapy system to deliver more powerful cancer treatments with pinpoint accuracy and precision. It uniquely integrates advanced imaging and motion management technologies within a sophisticated new architecture that makes it possible to deliver treatments more quickly while monitoring and compensating for tumor motion. While the technology always opens the door, it is always the skilful doctors who can get inside it.
Oesophageal Cancers and Radiation Therapy
Oesophgeal Cancers/ cancers of food pipe are divided into three types (depending on its location)– upper, middle and lower Esophgeal cancers --from the broad perspective of treatment.
Upper esophageal cancers are largely treated with radiation therapy and chemotherapy (Concurrent CTRT) given together for a total period of 6-7 weeks. In this Radiation therapy is generally given 5 days per week over 6-7 weeks using techniques like IMRT or IGRT with simultaneous chemotherapy given (using single or two drugs) on a once a week approach. At times depending your tumours location your oncologist might suggest adding additional therapy like Intra Luminal Brachytherapy (ILRT).
Middle and Lower third cancers are generally treated with Pre operative Radio Chemotherapy (pre op CTRT) followed by surgery after 6-8 weeks. In this Radiation therapy is generally given 5 days per week over 5 weeks using techniques like IMRT or IGRT with simultaneous chemotherapy given (using single or two drugs) on a once a week approach. Surgery is later performed after a gap of 6-8 weeks from completion of CTRT. In this kind of approach CTRT is used to shrink cancer and make it smaller before surgery. This is a world wide accepted approach to treating these cancers and at Max Institute of Cancer Care , we have been following this treatment approach for last 10 years.
However sometimes middle and lower third esophageal cancers might require a different approach like pre operative chemotherapy (instead of CTRT) or directly surgery (without pre op CTRT) or only CTRT (without surgery)—your oncologist will discuss all this with you after reviewing your case.
Rectal Cancers and Radiation Therapy
Majority rectal cancers are treated with pre operative chemo radiotherapy (Pre op CTRT), given over 5-6 weeks followed by surgery. In this, Radiation therapy is generally given 5 days per week over 5 weeks using techniques like IMRT or IGRT with simultaneous chemotherapy. Surgery is later performed after a gap of 6-8 weeks from completion of CTRT. In this kind of approach CTRT is used to shrink cancer and make it smaller before surgery and sometimes it also helps in saving natural anal sphincter (and avoid colostomy). This is a worldwide accepted approach to treating these cancers and at Max Institute of Cancer Care, we have been following this treatment approach for last 10 years. Some patients may receive short course radiotherapy over 5 days.
However occasionally these tumours might need a different approach like direct surgery (without pre op CTRT) or chemotherapy followed by surgery.
Anal Cancers and Radiation Therapy
Anal canal is lower most part of stool passage tube/organ. Its commonly affected by a type of carcinoma called as Squamous Cell Carcinoma (SCC). SCC of anal canal are highly sensitive to radiation therapy and chemotherapy. In majority patients, these tumours can be cured with Concurrent CTRT (Chemo Radiotherapy) without surgery. In this Radiation therapy is generally given 5 days per week over 5 -7 weeks using techniques like IMRT or IGRT with simultaneous chemotherapy. By avoiding surgery, it also avoids colostomy (artificial passage for clearing faeces).
Primary and Secondary Liver Cancers and SBRT
Liver cancers can be primary (arising from within liver) or secondary (spread/metastases from cancer elsewhere in body).
Both primary and secondary liver cancers are considered tough to treat. Whenever safe surgery is possible, they are treated with surgery. Sometimes for secondary liver cancers, surgery is done after few cycles of initial chemotherapy rather than upfront.
Whenever surgery is not feasible, patient is evaluated for SBRT. Every patient with liver cancer may or may not be suitable/fit for liver SBRT. Your radiation oncologist will assess for suitability for liver SBRT. At times liver SBRT is done after shrinking tumour using TACE (Trans arterial Chemo Embolization). At times for multiple liver tumour, we club more than treatments together – like we might treat few live cancers with SBRT while others might be treated with RFA (Radio Frequency Ablation). At times SBRT is used to treat tumour clot/thrombus within portal vein (Blood vessel within liver) called as Portal Vein Tumour Thrombus (PVTT) to facilitate TACE or Surgery after SBRT. Occasionally SBRT is used prior to liver transplant (called as Bridge to Transplant) especially when there is some waiting prior to liver transplant surgery.
SBRT involves treating liver cancer with very high doses of radiation therapy in a precise manner while sparing unaffected normal liver as much as possible. SBRT liver is a safe treatment in hand of a trained team. Till few years back Radiation was not even considered a treatment option in management of liver cancers due to poor tolerance of radiation by liver. Times have now changed and in present era it’s possible to safely treat liver tumours. Successful SBRT delivery requires 4 DCT Scanners, High end Linear Accelerators with IMRT, IGRT, Robotic couch, RPM systems which are all available across Max Hospitals. Sometimes a radio opaque marker is placed in liver under USG or CT guidance before starting SBRT. This treatment is usually given in 3-10 fractions over 1-2 weeks period. Success of SBRT procedure depends on multiple factors like size of tumour, general/functional health of liver, no of foci of cancers in liver and elsewhere in body. SBRT liver has very few side effects like – Fatigue, mild to moderate change in liver functions or mild to moderate fall in platelet counts.
Bile Duct Carcinomas (Cholangio carcinomas)
Surgery is the preferred treatment for non metastatic cholangio carcinomas. Radiation therapy is used in management of cholangiocarcinomas in three situations-
Post op RT after surgery especially if tumour cells are present at margins of surgical resection area or for lymph node positive disease. Generally, this radiation therapy is given over 5-6 weeks using IMRT/IGRT.
For cholangio carcinomas involving liver, liver resection or transplant is preferred treatment At times radiation therapy (SBRT) is used prior to liver transplant (called as Bridge to Transplant) especially when there is some waiting prior to liver transplant surgery.
Radical radiation therapy alone or with chemotherapy is used to treat cholangio carcinomas that are unsuitable for surgery.
Gall Bladder, Pancreas and Stomach Cancers and Radiation Therapy—
Radiation Therapy is at times used after surgery in gall bladder, pancreas and stomach cancers especially when cancers have spread to lymph nodes or it is present at surgical margins. This RT is generally given over 5-6 weeks using IMRT/IGRT techniques with or without concurrent chemotherapy.