Radiation therapy toxicity

Radiation colitis is obliterative-endarteritis injury to the colon and rectum from pelvic radiotherapy, presenting as a self-limited acute mucositis during or within 3 months of treatment, or as a progressive chronic vasculopathy 3 months to 2 years later with bleeding, stricture, and fistula. Diagnosis rests on radiotherapy history plus endoscopic appearance; management is sequenced from topical rectal therapy to endoscopic coagulation to surgery for structural complications.

Cancer treatment-related cardiotoxicity covers five distinct syndromes: irreversible, cumulative-dose-dependent anthracycline cardiomyopathy; typically reversible trastuzumab/HER2-targeted left ventricular dysfunction; radiation-induced coronary, pericardial, valvular, and conduction disease appearing years after chest irradiation; tyrosine kinase inhibitor and VEGF-inhibitor hypertension and QT prolongation; and immune checkpoint inhibitor myocarditis, a distinct fulminant entity requiring urgent high-dose corticosteroids and permanent drug discontinuation.

Hypothyroidism is thyroid hormone deficiency, most commonly caused by autoimmune (Hashimoto) thyroid failure in iodine-sufficient countries, diagnosed by an elevated thyroid-stimulating hormone with a low or normal free thyroxine. First-line treatment is levothyroxine dosed at 1.6 mcg/kg lean body weight orally once daily, titrated using thyroid-stimulating hormone rechecked no sooner than 6 weeks after any dose change.

Myelopathy is spinal cord dysfunction from extrinsic compression or intrinsic cord pathology, most often degenerative cervical spondylosis, producing combined upper and lower motor neuron findings. MRI of the suspected level confirms the diagnosis; management ranges from a 6 to 8 week conservative trial to emergent surgical decompression, antibiotics, or high dose glucocorticoids depending on cause.

Hodgkin lymphoma is a B-cell malignancy defined by Reed-Sternberg cells that classically presents with painless, contiguously spreading cervical or mediastinal lymphadenopathy in a young adult, and it is confirmed by excisional lymph node biopsy. Ann Arbor/Lugano stage and interim PET response drive risk-adapted ABVD chemotherapy with or without radiation, and most patients are cured.

Breast cancer is a malignancy of ductal or lobular epithelium, most often presenting as a firm, painless mass in the upper outer quadrant. Diagnosis rests on core needle biopsy with estrogen, progesterone, and HER2 receptor testing, and first-line treatment pairs breast-conserving surgery or mastectomy with sentinel node biopsy, radiation, and receptor-guided systemic therapy such as tamoxifen or trastuzumab.

Lung cancer is the leading cause of cancer death worldwide, split into non-small cell lung cancer (NSCLC, 80% of cases: adenocarcinoma, squamous cell, large cell) and small cell lung cancer (SCLC, 10-15%), both driven overwhelmingly by cigarette smoking. Diagnosis requires tissue histopathology, staging drives treatment (TNM staging for NSCLC, limited versus extensive stage for SCLC), and management ranges from lobectomy in early-stage disease through concurrent chemoradiation and consolidation immunotherapy in locally advanced disease to targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, or platinum-based chemotherapy in metastatic disease.

Esophageal cancer comprises squamous cell carcinoma, driven by tobacco, alcohol, and caustic or motility injury to the upper and mid esophagus, and adenocarcinoma, arising from GERD-driven Barrett esophagus distally, both presenting with progressive dysphagia from solids to liquids plus weight loss. Diagnosis is by upper endoscopy with biopsy, staged with CT, PET, and endoscopic ultrasound, and treatment is stage-directed from endoscopic resection through esophagectomy with perioperative chemotherapy or chemoradiation to palliative chemoradiation and stenting.

Constrictive pericarditis is a rigid, often calcified pericardium that impairs diastolic filling, causing predominantly right-sided heart failure. It follows pericardial injury (post-surgical, tuberculous, radiation, or idiopathic), is distinguished from restrictive cardiomyopathy by hemodynamic and imaging features, and definitive treatment is pericardiectomy.

Interstitial lung disease (ILD), also called diffuse parenchymal lung disease, is a diverse group of nonmalignant disorders causing inflammation and scarring of the alveolar interstitium, presenting as subacute to chronic exertional dyspnea and nonproductive cough. Diagnosis rests on pulmonary function testing plus high-resolution CT pattern recognition; management is exposure removal, glucocorticoids for inflammatory disease, antifibrotic therapy for progressive fibrotic disease, oxygen for hypoxemia, and early transplant referral.

Head and neck squamous cell carcinoma arises from the mucosal epithelium of the oral cavity, pharynx, and larynx along two pathways, tobacco/alcohol-driven and HPV-16-driven oropharyngeal disease, presenting with site-specific symptoms culminating in a new neck mass. Diagnosis requires laryngoscopy and biopsy of the primary with p16 testing, and treatment is single-modality surgery or radiation for early stage, cisplatin-based chemoradiation for locally advanced disease, and checkpoint inhibitors or cetuximab for recurrent or metastatic disease.

Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.

Hypersensitivity pneumonitis is a mixed type III/IV immune reaction to repeated inhalation of an organic antigen in a sensitized host, producing noncaseating granulomas and bronchiolocentric inflammation. Removal of the offending antigen is the essential first step in treatment; glucocorticoids are added for significant hypoxemia or symptom burden, and unremitting exposure can progress to fibrotic lung disease indistinguishable from idiopathic pulmonary fibrosis.