Radiation Oncology · Supplementary · from Radiation Oncology

Case 1: Adjuvant Radiation for Breast Cancer

Patient Presentation

Demographics: 52-year-old female marketing executive

Chief Complaint: "I had my lumpectomy for breast cancer and my surgeon says I need radiation to reduce the chance of it coming back."

History of Present Illness: A 52-year-old postmenopausal woman presents to the radiation oncology department for consultation regarding adjuvant radiation therapy following breast-conserving surgery (lumpectomy) for early-stage breast cancer. She was diagnosed 6 weeks ago after a screening mammogram revealed a 1.8 cm spiculated mass in the upper outer quadrant of her left breast. Ultrasound-guided core needle biopsy confirmed invasive ductal carcinoma, grade 2, ER+/PR+, HER2-negative, Ki-67 18%.

She underwent lumpectomy with sentinel lymph node biopsy 3 weeks ago. Surgical pathology confirmed a 2.1 cm invasive ductal carcinoma with negative margins (closest margin 4 mm), no lymphovascular invasion, and 0/3 sentinel lymph nodes positive for metastatic disease. Final pathologic stage: pT2N0M0, Stage IIA. Oncotype DX recurrence score was 16 (low-intermediate), supporting endocrine therapy alone without adjuvant chemotherapy.

She has been referred for adjuvant whole-breast radiation therapy with consideration of boost to the tumor bed. She is anxious about potential side effects, particularly cardiac toxicity given that the left breast is being treated.

Past Medical History:

• Breast cancer (newly diagnosed, as above)
• Hypertension, well-controlled
• Gastroesophageal reflux disease
• No prior radiation exposure
• Menopausal since age 49

Medications:

• Amlodipine 5 mg daily
• Omeprazole 20 mg daily
• Recently started anastrozole 1 mg daily (aromatase inhibitor)

Social History:

• Marketing executive, works full-time
• Non-smoker
• Social wine drinker (1-2 glasses per week)
• Divorced, two adult children
• Exercises regularly (yoga, walking)

Family History:

• Mother: breast cancer at age 68 (ER+, treated with mastectomy)
• Father: hypertension
• Genetic testing: BRCA1/2 negative

Physical Examination

• Vital Signs: BP 128/76 mmHg, HR 72 bpm, RR 14/min, Temp 36.8°C, SpO2 99% on room air
• General: Well-appearing female in no acute distress
• Left breast: Well-healed lumpectomy incision in UOQ, mild residual ecchymosis, no seroma, no skin changes; breast cosmesis good
• Right breast: Normal, no masses
• Lymph nodes: No palpable axillary, supraclavicular, or cervical lymphadenopathy bilaterally
• Cardiovascular: Regular rate and rhythm, no murmurs
• Lungs: Clear bilaterally
• Chest wall: Normal, no tenderness

Workup and Results

Laboratory Studies:

Surgical Pathology Summary:

Radiation Treatment Planning:

• CT simulation: Patient positioned supine on wing board with left arm abducted; 3 mm CT slices through thorax; respiratory assessment performed
• Target volumes:
• Clinical Target Volume (CTV): Entire left breast tissue (whole breast CTV)
• Boost CTV: Tumor bed with 1.5 cm expansion (guided by surgical clips)
• Planning Target Volume (PTV): CTV + 5 mm expansion for setup uncertainty
• Organs at risk (OAR) dose constraints:
• Heart: Mean dose <4 Gy (QUANTEC); V25Gy <10%
• Left anterior descending artery (LAD): Mean dose <10 Gy
• Ipsilateral lung: V20Gy <30%; mean lung dose <15 Gy
• Contralateral breast: Mean dose <3 Gy

Clinical Image

Diagram showing radiation treatment planning for left breast cancer, illustrating tangential beam arrangement, dose distribution with color wash, and critical organ-at-risk structures (heart, LAD artery, ipsilateral lung) with deep inspiration breath hold (DIBH) technique. Source: Educational illustration.

Diagnosis

Left Breast Invasive Ductal Carcinoma, pT2N0M0, Stage IIA, ER+/PR+/HER2-, Status Post Breast-Conserving Surgery, Requiring Adjuvant Whole-Breast Radiation Therapy

Key Diagnostic Criteria:

• Invasive ductal carcinoma confirmed on surgical pathology
• Breast-conserving surgery with negative margins
• Node-negative disease (0/3 sentinel nodes)
• Adjuvant radiation therapy is standard of care after lumpectomy, reducing ipsilateral breast recurrence from ~30% to ~10% at 10 years
• Left-sided breast cancer requiring cardiac-sparing techniques

Treatment Plan

1. Whole-breast radiation: Hypofractionated regimen -- 40 Gy in 15 fractions (2.67 Gy/fraction) over 3 weeks to the whole breast (per UK FAST-Forward trial and ASTRO guidelines for hypofractionation)
2. Tumor bed boost: 10 Gy in 4 fractions (2.5 Gy/fraction) to the lumpectomy cavity (age 52 with grade 2 tumor; boost reduces local recurrence by an additional 50% relative risk reduction)
3. Cardiac-sparing technique: Deep inspiration breath hold (DIBH) for all fractions -- patient holds breath during treatment, displacing heart away from treatment field; target mean heart dose <2 Gy
4. Treatment technique: Tangential field-in-field IMRT (forward-planned) to improve dose homogeneity across the breast; daily image guidance with surface-guided radiation therapy (SGRT) for setup verification
5. Side effect management:

• Skin care: Aquaphor or aloe-based moisturizer to treatment area starting week 1; avoid irritants
• Fatigue: Expected mild-moderate; continue exercise as tolerated
• Monitor for radiation dermatitis (expected peak 1-2 weeks after completion)

1. Continue anastrozole: 1 mg daily for planned 5-10 years of adjuvant endocrine therapy
2. Follow-up: Post-treatment evaluation at 4-6 weeks; mammography at 6 months post-RT (new baseline); annual surveillance mammography thereafter

Key Learning Points

• Adjuvant whole-breast radiation after breast-conserving surgery reduces the 10-year ipsilateral breast recurrence rate by approximately two-thirds and provides a modest overall survival benefit
• Hypofractionated whole-breast radiation (40 Gy/15 fractions or 42.5 Gy/16 fractions) is now the standard of care for most patients, with equivalent efficacy and comparable or improved toxicity compared to conventional fractionation (50 Gy/25 fractions)
• Deep inspiration breath hold (DIBH) is a critical cardiac-sparing technique for left-sided breast radiation, reducing mean heart dose by 40-60% compared to free-breathing treatment
• The tumor bed boost provides an additional absolute local recurrence benefit of 3-4% at 20 years, with the greatest benefit in younger patients (<50 years)
• Radiation planning for breast cancer requires careful attention to organs at risk, particularly the heart (long-term cardiovascular risk), LAD artery, and ipsilateral lung

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