Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed diagnosis of primary invasive breast cancer or ductal
carcinoma in situ

- Planning to undergo ≥ 5 weeks of continuous definitive or adjuvant external-beam
radiotherapy to 1 of the following sites:

- Whole breast (as part of breast-conservation therapy)

- Chest wall (as part of post-mastectomy irradiation)

- Treatment of regional lymph nodes (i.e., axillary, supraclavicular, or
internal mammary) allowed

- Must meet the following criteria for planned radiotherapy:

- Planned total radiation dose ≥ 5,000 Gy and daily radiation dose between 1.75
and 2.12 Gy

- No planned split-course radiotherapy

- No partial breast treatment, defined as treatment of < 75% of the breast
parenchyma

- Intensity-modulated radiotherapy planning and delivery, conventional
radiotherapy, or 3-dimensional radiotherapy techniques allowed

- Must be entered on study within 7 days prior to beginning radiotherapy

- Must start study drug prior to receiving the third radiotherapy fraction

- No preexisting skin breakdown within the planned radiotherapy field at the time of
study entry

- No bilateral breast cancer treatment

- No inflammatory carcinoma of the breast

- Hormone receptor status not specified

PATIENT CHARACTERISTICS:

- Male or female

- Menopausal status not specified

- ECOG performance status 0-2

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- Able to complete questionnaires independently or with assistance

- No known allergy or hypersensitivity to mometasone furoate (Elocon® or generic
cream), imidazolidinyl urea, or formaldehyde

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- No prior radiotherapy to the planned radiotherapy treatment area

- No concurrent or planned leukotriene inhibitors, including the following:

- Zafirleukast

- Monteleukast

- Zileuton

- No concurrent or planned use of any prescription or over-the-counter medications
containing hydrocortisone or any other cortisone or steroid-containing preparations
(systemic, local, or topical) including, but not limited to, the following creams or
ointments:

- Cortaid®

- Cortizone 10®

- Tucks®

- Preparation H®

- No other concurrent topical agents (e.g., lotions, aloe vera) to radiotherapy field
during study treatment