CHAPTER 2: Basics of Oncology and Pathology

Radiation therapy techniques have evolved for more than a century. At present, the majority of patients are treated with teletherapy (ie, external radiation). Teletherapy treatment modalities include electromagnetic radiation (ie, X-rays and gamma rays) and particulate radiation (electrons, protons, neutrons, and heavy ions). Brachytherapy involves implantation of radioactive sources into the tumor tissues, on either a temporary or a permanent basis. Dose escalation and hypofractionation can benefit patients with radiation-resistant tumor types, including sarcoma, melanoma, renal cell carcinoma, and colorectal metastases.¹

A 54-year-old woman is diagnosed with inoperable FIGO stage IIIB squamous cell carcinoma of the uterine cervix on the basis of pelvic wall involvement. As per NCCN² guidelines, she is dispositioned for cisplatin-based chemoradiation with curative intent.

• Radiation treatment planning and delivery: Optimal radiation therapy for cervical carcinoma involves both teletherapy and brachytherapy components, with the brachytherapy component being essential for optimal cure rates, as this modality allows for dose escalation to the tumor while minimizing the dose to adjacent healthy structures¹

• A customized treatment plan is developed that includes intensity-modulated radiation therapy (IMRT) to the pelvis followed by multisession intracavitary brachytherapy to the cervical tumor¹

Owing to advances in computational delivery, and in parallel to the development of sophisticated 3-dimensional volumetric imaging (including CT, PET, and MRI), radiation therapy has quickly evolved from 2-dimensional treatment planning to 3- and 4-dimensional delivery over the past 2 decades.¹

At present, dose delivery is tailored to the 3-dimensional volume of the tumor. The most sophisticated techniques use inverse planning methods, whereby dose delivery is optimized through computer-generated fluence maps.¹ IMRT remains the most common treatment modality for advanced teletherapy delivery. Particulate delivery with protons and heavy ions is also being evaluated, with physical advantages noted for certain specific applications (including pediatric brain tumors and chordomas at the base of the skull), owing to specific energy deposition differences in those modalities. The use of proton therapy for other tumor sites is under investigation.¹

A number of sophisticated radiation treatment modalities allow for increasing treatment options for treatment of multiple disease sites.

1. National Comprehensive Cancer Network (NCCN) guidelines. Version 2.2017. Available at: www.nccn.org.

2. Halperin EC, Brady LW, Perez CA, et al. Perez and Brady’s Principles and Practice of Radiation Oncology. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2013.

Brain metastases are common sequelae of solid tumors (lung, breast, melanoma, renal, and colorectal). Lung cancer has the highest number of brain metastases; however, melanoma has the highest propensity to metastasize to brain. Although their exact incidence is unknown, about 8%–10% of patients with cancer will manifest brain metastasis, with an expected ...