5.7 Lymphoma, Sarcoma, Skin, Leukemia & Oncologic Emergencies

Lymphoma: Hodgkin vs. Non-Hodgkin

Lymphomas arise from lymphoid tissue and are separated into two biologically distinct categories:

• Ann Arbor staging (Stages I–IV, with A/B for absence/presence of systemic symptoms such as fever, night sweats, weight loss) classifies both Hodgkin and non-Hodgkin lymphoma by the number and location of involved nodal regions and whether extranodal/extralymphatic sites are involved.
• Hodgkin lymphoma is managed with combination chemotherapy, with involved-site radiation therapy (ISRT) added for bulky disease, residual PET-positive disease, or as consolidation in early-stage favorable disease — a shift from historically larger "involved-field" or "extended-field" volumes toward smaller, PET/CT-defined target volumes to reduce late toxicity (secondary malignancy, cardiac disease) in long-surviving patients.
• NHL is more often chemotherapy-predominant; radiation is used for consolidation of bulky/residual disease, for indolent subtypes as definitive low-dose therapy, or palliatively.

Soft Tissue Sarcoma

Sarcomas arise from mesenchymal tissue (muscle, fat, connective tissue, bone) rather than epithelium, distinguishing them biologically from the carcinomas that make up most solid tumors. Extremity soft tissue sarcomas are managed with limb-sparing surgical resection combined with radiation (pre- or postoperative) to maximize local control while preserving limb function — a strategy that replaced amputation as the standard of care. Radiation fields typically follow the longitudinal muscle compartment rather than a simple margin around the tumor, because sarcomas spread along fascial planes and muscle bundles rather than uniformly in all directions.

Skin Cancer

• Basal cell carcinoma (BCC) is the most common skin cancer, slow-growing, and rarely metastasizes; superficial radiation therapy (SRT) or electron beam therapy is effective for lesions where surgery is undesirable (e.g., cosmetically sensitive facial sites, poor surgical candidates).
• Squamous cell carcinoma (SCC) of the skin has a higher metastatic potential than BCC, particularly in immunosuppressed patients or lesions with perineural invasion; radiation is used definitively or adjuvantly, with attention to regional (parotid, cervical, or inguinal) nodal basins depending on location.
• Melanoma arises from melanocytes and has the highest metastatic potential of the common skin cancers. Radiation's primary role is adjuvant (after wide local excision and/or lymph node dissection) for high-risk features (thick lesions, positive margins, extensive nodal involvement) or palliative for metastatic disease (notably brain metastases), since melanoma is not considered a routinely radiosensitive tumor in the way basal or squamous cell carcinoma can be.
• Mycosis fungoides (cutaneous T-cell lymphoma) can be treated with total skin electron beam therapy (TSEBT), a specialized technique using multiple electron fields and patient positioning (e.g., a six-dual-field rotational technique) to deliver a uniform dose to the entire skin surface while sparing deeper structures.

Leukemia and the Role of Total Body Irradiation

Leukemias are malignancies of blood-forming cells in the bone marrow and are not typically treated with localized radiation as primary therapy, since disease is diffusely distributed throughout the marrow and bloodstream. Radiation's principal role is total body irradiation (TBI) as part of conditioning regimens before hematopoietic stem cell (bone marrow) transplantation — TBI ablates residual malignant marrow and provides immunosuppression to permit donor cell engraftment. TBI planning requires unique considerations: extended treatment distances, lung dose-limiting blocks (to reduce pneumonitis risk), and rigorous in-vivo dosimetry to confirm uniform dose across the entire body.

Oncologic Emergencies

Oncologic emergencies require immediate recognition and rapid intervention (which may include emergent radiation therapy) because delay can cause permanent disability or death.

The therapist's role in recognizing these emergencies is critical: a patient who reports new leg weakness and urinary retention during a treatment course for known spinal metastases must be reported immediately, since spinal cord compression treated within hours of symptom onset has a dramatically better chance of neurologic recovery than compression treated after paralysis has set in. Similarly, new facial swelling or breathlessness in a patient with a mediastinal mass should raise concern for SVC syndrome and prompt urgent physician notification.

Summary Table: Site-Specific Radiosensitivity Patterns

Understanding relative radiosensitivity across sites explains why some tumors (Hodgkin lymphoma) can be treated with modest doses while others (sarcoma, melanoma) require higher, more aggressive dose regimens or combined-modality approaches to achieve local control.