Management of Side Effects of Cancer Therapy and Radiation Therapy

Radiation therapy and pharmacologic cancer therapy — conventional cytotoxic chemotherapy and the growing range of targeted small-molecule and biologic agents — cause toxicities that are, in large part, predictable extensions of how these treatments work. Cytotoxic chemotherapy exploits the high proliferation rate of cancer cells, but the same mechanism damages other rapidly-dividing normal tissue: the oral and gastrointestinal mucosa, the skin and its appendages, and the bone marrow. Radiation causes locally-confined injury along its entry-to-exit path through tissue, with early toxicities appearing within days to months and delayed toxicities appearing months to years later. Targeted agents cause a different, drug-specific toxicity pattern rather than the classic cytotoxic pattern, but the management principle is the same: most of these toxicities are foreseeable, and a pharmacist who anticipates them, counsels proactively, and intervenes early can prevent an unplanned dose reduction, treatment delay, or discontinuation of otherwise effective anticancer therapy.^[1] This chapter covers oral mucositis, chemotherapy-induced diarrhea, hand-foot syndrome/hand-foot skin reaction, radiation dermatitis, chemotherapy-induced peripheral neuropathy, the emergency recognition of febrile neutropenia, and extravasation of vesicant chemotherapy — plus the patient-education and self-monitoring counselling role woven through all of them. Chemotherapy-induced nausea and vomiting is covered separately in its own chapter and is not duplicated here.

Severity for each toxicity below is generally described using the NCI Common Terminology Criteria for Adverse Events (CTCAE) Grade 1-5 scale: Grade 1 is mild and usually needs no intervention; Grade 2 is moderate and may limit instrumental activities of daily living; Grade 3 is severe, limits self-care, and often needs hospitalization or urgent intervention; Grade 4 is life-threatening; Grade 5 is death. Specific grade thresholds that change management are called out within each toxicity below rather than reproduced here as one generic table.^[2]

• Oral mucositis: most traditional cytotoxic chemotherapy regimens carry some risk (severity varies by agent and individual); higher-risk classes include mTOR inhibitors, EGFR inhibitors, CDK4/6 inhibitors, and BCL-2 inhibitors; head and neck or upper gastrointestinal radiation; poor baseline oral hygiene or pre-existing dental disease.
• Chemotherapy-induced diarrhea: essentially all traditional cytotoxic agents carry some dose-related risk; irinotecan-based and fluoropyrimidine-based regimens are particularly implicated; pelvic or abdominal radiation.
• Hand-foot syndrome/HFSR: capecitabine, fluorouracil, and liposomal doxorubicin for classic hand-foot syndrome; BRAF inhibitors and multikinase VEGF inhibitors for hand-foot skin reaction; friction or heat exposure to palms/soles during treatment.
• Radiation dermatitis: higher total radiation dose and fraction size; treatment field location, especially skin folds (breast, axilla, groin, neck); concurrent chemotherapy or targeted therapy; prior radiation to the same field; smoking; larger breast size in breast radiation.
• Chemotherapy-induced peripheral neuropathy: cumulative dose of a neurotoxic agent (platinums, taxanes, vinca alkaloids, proteasome inhibitors); pre-existing peripheral neuropathy of any cause, including diabetic neuropathy; combination regimens using more than one neurotoxic agent.
• Febrile neutropenia: regimen- and individual-specific neutropenia risk; dose-dense or heavily myelosuppressive regimens; a prior episode of febrile neutropenia on the same regimen; poor baseline marrow reserve.
• Extravasation: peripheral rather than central venous access for a vesicant drug; fragile, small, or previously-used veins; a patient unable to report pain/burning during infusion; a prolonged infusion through a peripheral line.

Distinguishing hand-foot syndrome from hand-foot skin reaction

Distinguishing chemotherapy-induced diarrhea from an infectious cause

Do not automatically attribute new diarrhea in a patient on active cancer therapy to the chemotherapy itself. Obtain stool culture and Clostridioides difficile toxin/PCR testing when any of the following are present: fever, recent antibiotic use or hospitalization, blood in the stool, grade 3 or higher diarrhea, or diarrhea in a neutropenic patient — testing is not routinely needed for mild, uncomplicated diarrhea that is temporally linked to a known diarrheagenic regimen and has none of these features.^[4]

History and examination

• Confirm the timing of new symptoms relative to the most recent treatment cycle or radiation fraction, and identify the specific causative agent(s) in the regimen.
• Ask specifically about oral intake (mucositis), stool frequency/consistency and hydration status (diarrhea), palm/sole symptoms and functional impact on grip/walking (HFS/HFSR), the radiation field and any skin-fold involvement (radiation dermatitis), and sensory/motor symptoms plus fall risk (CIPN).
• Examine the oral mucosa directly for erythema, ulceration, and extent; examine palms/soles using the HFS-vs-HFSR pattern above; examine the radiated skin field specifically, not just visible exposed skin; perform a focused sensory examination (light touch, vibration), check deep tendon reflexes, and observe gait for CIPN.
• Review the full medication list for other agents that could compound a given toxicity, e.g. another neurotoxic or nephrotoxic drug alongside a neurotoxic chemotherapy agent.

When testing is not indicated

• Routine imaging is not needed for uncomplicated HFS/HFSR or radiation dermatitis — both are clinical diagnoses based on exposure history and exam findings.
• Nerve conduction studies are not routinely needed for typical CIPN — reserve for atypical presentations or genuine diagnostic uncertainty.
• Stool testing is not needed for mild, uncomplicated diarrhea without the red-flag features above.

• Prevent each toxicity where a genuine preventive measure exists, by identifying risk factors before treatment starts.
• Detect toxicity early and treat promptly to reduce severity and prevent downstream complications (dehydration, secondary infection, tissue necrosis).
• Control symptoms adequately to preserve the patient's oral intake, mobility, and quality of life.
• Avoid an unplanned dose reduction, treatment delay, or discontinuation of otherwise effective anticancer therapy caused by a toxicity that could have been prevented or managed proactively.
• Recognize and immediately escalate the toxicities that are true emergencies — febrile neutropenia, severe extravasation injury, severe mucositis preventing intake, and severe diarrhea with dehydration.

• Oral mucositis: soft-bristled toothbrush replaced regularly, gentle flossing (avoid if gums bleed), avoid hard/sharp/spicy/acidic foods, avoid alcohol- and peroxide-containing mouth products.
• Diarrhea: a bland, low-residue, low-fat diet (e.g. bananas, rice, applesauce, toast) during an active episode; adequate oral fluid/electrolyte replacement; avoid caffeine, alcohol, and high-fibre or high-fat foods until resolved.
• Hand-foot syndrome/HFSR: avoid prolonged hot-water exposure, tight or ill-fitting footwear, and repetitive friction/pressure activities (running, manual labour, tight grip tools) on hands and feet.
• Radiation dermatitis: loose, soft clothing over the treatment field; avoid adhesive tape directly on treated skin; use an electric razor rather than a blade if shaving is needed in the field; protect the field from sun exposure during and after treatment.
• Peripheral neuropathy: fall-prevention measures (clear walkways, adequate lighting, supportive footwear); avoid extremes of temperature on hands/feet; use caution with sharp objects and hot surfaces given reduced sensation.
• Infection-prevention hygiene during periods of expected neutropenia: frequent hand hygiene, avoiding large crowds and people with active respiratory illness, avoiding undercooked meat/eggs and unpasteurized dairy, and prompt attention to cuts, burns, or skin breaks.
• Extravasation prevention: careful IV site selection with confirmed blood return before and during a vesicant infusion, and central venous access for high-risk vesicants requiring prolonged infusion.

Pregnancy

Cancer therapy in pregnancy is managed jointly with maternal-fetal medicine and is beyond this chapter's scope, but for the toxicities covered here: bland oral rinses, basic skin care, and topical moisturizers/emollients are compatible with pregnancy. Loperamide and diphenoxylate/atropine are used cautiously and generally reserved for when non-pharmacologic measures are inadequate. Octreotide has limited pregnancy data and should be reserved for genuinely refractory diarrhea after specialist discussion. Duloxetine, gabapentin, pregabalin, and venlafaxine each carry their own pregnancy-specific considerations independent of the CIPN indication — confirm with the treating oncology team before starting any of them in a pregnant patient.

Breastfeeding

Topical products used at standard doses for radiation dermatitis and hand-foot syndrome (moisturizers, low-to-medium-potency topical corticosteroids, topical diclofenac) are generally compatible with breastfeeding given minimal systemic absorption. Loperamide is compatible with breastfeeding. Octreotide and dexrazoxane have limited breastfeeding data; discuss individually with the oncology team.

Pediatrics

This chapter focuses on adult dosing and adult-specific regimens — the loperamide high-dose regimen above, for example, is not a pediatric dose. The same toxicity syndromes occur in children treated for cancer, but doses, some agent choices, and grading nuances differ; consult pediatric oncology-specific dosing resources rather than extrapolating adult doses by simple weight-based scaling.

Older adults

Older adults are at higher risk of dehydration from chemotherapy-induced diarrhea and of falls from both CIPN and gabapentinoid sedation — reinforce fall-prevention counselling explicitly when starting gabapentin, pregabalin, or venlafaxine for CIPN in this group.

Renal impairment

Gabapentin and pregabalin require dose reduction in renal impairment. Octreotide and dexrazoxane should be used cautiously with close monitoring in significant renal impairment. Loperamide does not require renal dose adjustment at standard doses.

• Oral mucositis: reassess oral intake, pain control, and mucosal appearance at each contact during active treatment; watch for secondary oral candidiasis (persistent white plaques) in a patient with ongoing mucositis, especially if immunosuppressed.
• Diarrhea: track stool frequency/consistency and hydration status; confirm resolution before the next treatment cycle where possible, since ongoing diarrhea affects dosing decisions.
• Hand-foot syndrome/HFSR: examine palms/soles at each visit in a patient on a causative agent; grade severity consistently to guide dose-modification decisions.
• Radiation dermatitis: assess the treatment field weekly during radiation and for several weeks after completion, since peak severity is often reached after treatment ends rather than during it.
• CIPN: reassess sensory/motor symptoms and functional impact (grip, gait, falls) before each cycle of a neurotoxic agent — this, not a fixed cycle count, is what actually drives dose-modification decisions.
• Neutropenia risk: review the neutrophil-count nadir pattern each cycle in patients on myelosuppressive regimens, and confirm the patient knows to seek immediate care for fever rather than waiting for a scheduled visit.
• Extravasation site: reassess at 24-48 hours and again over the following 1-2 weeks for evolving pain, blistering, or skin breakdown, since the full extent of injury can take days to become apparent.

Oral mucositis not improving

1. Confirm the basic oral-care regimen is actually being followed, and reassess whether a preventive opportunity (cryotherapy, dexamethasone rinse) was missed on the last cycle if applicable to the regimen.
2. Rule out secondary oral candidiasis or herpes simplex reactivation as a cause of persistent or worsening pain.
3. Escalate analgesia stepwise — topical/local measures, then systemic non-opioid, then opioid analgesia — rather than leaving grade 3-4 pain undertreated.
4. If intake remains inadequate despite escalated analgesia, involve the oncology team regarding nutritional support and whether the causative regimen needs to be held or modified.

Diarrhea not improving

1. Confirm the patient used the correct regimen (standard vs high-dose loperamide) for their situation and took it consistently.
2. Reconsider an infectious cause — stool culture and C. difficile testing — if not already done, especially with fever, recent antibiotics, or bloody stool.
3. If diarrhea persists beyond 48 hours on the high-dose loperamide regimen, stop loperamide and escalate to octreotide with IV fluid support.
4. Hold the causative chemotherapy until diarrhea has fully resolved before the next planned cycle.

HFS/HFSR not improving

1. Confirm the patient is actually applying topical therapy consistently and avoiding known aggravating exposures (heat, friction).
2. Reassess severity grade formally rather than relying on the patient's subjective description — this determines whether a dose hold/reduction is now indicated.
3. If grade 2 or higher despite topical measures, hold the causative drug until resolved to grade 1 or lower, then resume at a reduced dose per the regimen's specific modification guide.
4. For recurrent grade 3 HFS/HFSR despite dose reduction, discuss discontinuation of the causative agent with the oncology team.

Radiation dermatitis worsening

1. Confirm basic skin-care measures are being followed and that nothing irritating (perfumed products, adhesive tape directly on skin) is being applied to the field.
2. Escalate from a low-potency to a medium/high-potency topical corticosteroid, or add a barrier film, if not already used.
3. For moist desquamation, switch to moist-wound-healing dressings rather than continuing a dry-skin-care approach.
4. Involve the radiation oncology team regarding a treatment interruption if the reaction is severe.

CIPN progressing despite treatment

1. Confirm duloxetine has been trialled, or document the specific reason it was not, before concluding no pharmacologic option remains.
2. Reassess functional impact specifically — grip strength, gait, falls — since this, not the sensory description alone, should drive an urgent dose-modification conversation with the oncology team.
3. Discuss dose reduction, extending the interval between cycles, or discontinuing the causative agent with the oncology team once CIPN meaningfully affects function.

• Treating new diarrhea in a cancer patient as automatically chemotherapy-related without considering an infectious cause, especially with fever, recent antibiotics, or bloody stool.
• Using standard OTC loperamide dosing for irinotecan-induced or refractory chemotherapy diarrhea instead of the high-dose regimen this specific situation requires.
• Continuing the high-dose loperamide regimen beyond 48 hours without response instead of escalating to octreotide.
• Using oral cryotherapy or cold foods with an oxaliplatin-containing regimen — cold exposure can trigger oxaliplatin's acute laryngopharyngeal dysesthesia.
• Recommending chlorhexidine mouth rinse or sucralfate for oral mucositis prevention/pain — both were specifically found not to work for this indication despite historical use.
• Recommending aloe vera, honey-based products, or vitamin C/D preparations for radiation dermatitis — current consensus evidence found against all of them despite continued popular use.
• Treating a patient's fever as low priority because they "don't look that sick" — clinical appearance is not a reliable filter in a neutropenic patient; the neutrophil count, not the vital signs alone, defines the emergency.
• Removing the IV cannula immediately after recognizing extravasation — it should stay in place first, to allow aspiration and antidote administration.
• Assuming any topical/oral agent linked from this chapter's Drug Database is available at the exact strength or formulation the evidence describes — confirm the dispensed product's strength (e.g. diclofenac diethylamine gel strength) matches what was actually studied.
• Offering acetyl-L-carnitine to try to prevent CIPN — trial evidence shows it does not prevent neuropathy and may worsen it.

How to use this table: doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment and the specific regimen's own dose-modification guide. Select any drug name to open its complete Pharmasist Drug Database page. Antibiotic selection and G-CSF dosing for febrile neutropenia are covered in the companion Infections in the Cancer Patient chapter, not reproduced here.^[3]

Oral mucositis

Basic oral hygiene and bland saline/bicarbonate rinses remain first-line for every patient; the agents below are targeted additions.^[1]

Not recommended despite historical use: chlorhexidine mouth rinse (does not prevent radiation-associated mucositis) and sucralfate, topical or systemic (does not prevent or treat mucositis pain).^[1]

Chemotherapy-induced diarrhea

Distinguish from an infectious cause before treating; see Assessment & Diagnosis.^[4]

Hand-foot syndrome and hand-foot skin reaction

Prevention and topical therapy are the same for both entities; dose modification thresholds are grade-based.^[6]

Radiation dermatitis

Reflects the current MASCC Delphi-consensus recommendations.^[8]

Not recommended despite historical/traditional use: aloe vera-based products, honey-based products, and vitamin C or vitamin D preparations — current consensus evidence found against all of them.^[8]

Chemotherapy-induced peripheral neuropathy

No agent is recommended for prevention.^[9]

Specifically not recommended for prevention: acetyl-L-carnitine — trial evidence shows it does not prevent CIPN and may worsen it.^[9]

Extravasation antidotes

Choose the antidote and thermal-compress direction by extravasated drug class; see Choose Initial Treatment.^[10]