Radiation Doses and Fractionation Schedules in Non-low Risk Ductal Carcinoma In Situ (DCIS) of the Breast

Inclusion Criteria:

Patients must fulfill all of the following criteria for admission to study:

* Women ≥ 18 years.
* Histologically proven DCIS of the breast without an invasive component.
* Bilateral mammograms performed within 6 months prior to randomization.
* Clinically node-negative.
* Treated by breast conserving surgery (primary excision or re-excision) with complete microscopic excision and clear radial margins of ≥1 mm\* (\*Patients with superficial or deep resection margin of \<1 mm are eligible if surgery has removed all of the intervening breast tissue from the subcutaneous tissue to the pectoralis fascia).
* Women who are at high risk of local recurrence due to:

  * Age \< 50 years; OR
  * Age ≥ 50 years plus at least one of the following:

    * Symptomatic presentation
    * Palpable tumour
    * Multifocal disease
    * Microscopic tumour size ≥ 1.5 cm in maximum dimension
    * Intermediate or high nuclear grade
    * Central necrosis
    * Comedo histology
    * Radial\* surgical resection margin \< 10 mm. (\*Patients with superficial or deep resection margin of \< 10 mm are eligible if surgery has not removed all of the intervening breast tissue from the subcutaneous tissue to the pectoralis fascia.)
* Assessed by surgeon and radiation oncologist to be suitable for breast conserving therapy including whole breast RT.
* Ability to tolerate protocol treatment.
* Protocol RT should preferably commence within 8 weeks but must commence no later than 12 weeks from the last surgical procedure.
* ECOG performance status 0, 1 or 2.
* Patient's life expectancy \> 5 years.
* Availability for long-term follow-up.
* Written informed consent.

Exclusion Criteria:

Patients who fulfill any of the following criteria are not eligible for admission to study:

* Multicentric disease or extensive microcalcifications that could not be completely excised by breast conserving surgery with radial margins of ≥1 mm\*.

  \*Patients with superficial and/or deep margin of \<1 mm are eligible if surgery has removed all of the intervening breast tissue from the subcutaneous tissue to the pectoralis fascia.
* Presence of tumour cells in lymph nodes detected using H\&E or immunohistochemical examination (if lymph node biopsy or dissection has been performed).
* Locally recurrent breast cancer.
* Previous DCIS or invasive cancer of the contralateral breast.

  * Bilateral DCIS of the breasts
  * Synchronous invasive carcinoma of the contralateral breast
* Other concurrent or previous malignancies except:

  * Non-melanomatous skin cancer;
  * Carcinoma in situ of the cervix or endometrium; and
  * Invasive carcinoma of the cervix, endometrium, colon, thyroid and melanoma treated at least five years prior to study admission without disease recurrence.
* Serious non-malignant disease that precludes definitive surgical or radiation treatment (e.g., scleroderma, systemic lupus erythematosus, cardiovascular/pulmonary/renal disease).
* ECOG performance status ≥ 3.
* Women who are pregnant or lactating.