Low dose radiation cause:
A i.e. Lung cancer; B i.e. AML; C i.e. Cervical cancer Intensity modulated (IM) is most suitable for prostate cancersQ (b/o reduced rectal toxicity) gynaecological cancer eg endometrial cancer (d/t reduced gastrointestinal > genitourinary and bone marrow toxicity) large lung tumors close to esophagus (but issues regarding lung motion, dose calculation accuracy need to be addressed and clinical data is sparse). - Reducing rectal toxicity is major dose limiting factor in therapy of prostate cancer, may allow dose escalation and a potential for improved cure rates. Paial sparing of rectal wall seems to be a the major advantage of IM, which allow higher than standard doses to be delivered to the prostate. So IM with daily image guidance has become routine to treat definitive prostate cancer. Radiation induced cancers include thyroid carcinoma, breast carcinoma and sarcomasQ (osteogenic sarcoma> fibrosarcoma> chondrosarcoma> malignant fibrous histiocytoma)- Wolfgang Secondary malignant tumors after total body irradiation (TBI) include acute myelogenous leukemia (AML)Q, myelodysplastic disease (MDS), post hematopoietic stem cell transplant lymplwproliferative disorder (PTLD), and solid tumors such as oral cavity, pharyngeal, liver, central nervous system, thyroid, bone and soft tissue cancers and melanomas. - Risk of radiation induced second malignancy is higher in ceain patients including children and young adults, those with known genetic predisposition to cancer (eg Li-Fraumeni, Lynch, Cowden and Gardner's syndrome), immuno compromized individuals and those with known exposure to other carcinogen (eg chemotherapy tobacco, alcohol etc). Use of highly conformal, intensity modulated radiation therapy designed specifically to deliver lower doses to normal tissues immediately surrounding the tumor, but at the expense of direct, leaked or scattered dose to larger volumes of body (ie large volumes and low doses) tend to be those most associated with radiation carcinogenesis. - Hodgkin's lymphoma surviors have risk of breast and lung cancercervical carcinoma surviors have risk of leukemia and sarcomaQ, and long term surviors of childhood retinoblastoma have risk of sarcomas as second malignancy. Exposure to ionizing radiation () may cause meningiomas, gliomasQand schwannomasQ and immunosuppression is a risk factor for primary CNS lymphoma (Harrison 3383). There is increased risk of secondary neoplasia in any organQ (eg bone, soft tissues, brain thyroid, salivary glands, eyes, hea, lung, kidney, liver, intestine, gonads etc), depending on the irradiation field after radiation therapy (Harrison 839 table).
Lung cancer
AML
Cervical cancer
All