Young Adult With Malignant Phyllodes Undergoing Adjuvant Radiotherapy With Bolus

ABSTRACT Malignant phyllodes tumor of the breast (MPTB) is a rare fibroepithelial tumor and very uncommon among young adult women. It has a higher likelihood of local recurrence (LR) compared to other phyllodes tumors of the breast. Due to limited data, there is no established consensus regarding adjuvant radiotherapy for MPTB. Post‐Mastectomy Radiotherapy (PMRT) reduces the risk of LR and breast cancer mortality. A bolus can be used to treat LR by counteracting the skin‐sparing effect, as well as in cases where body habitus or tissue expander location may require a bolus to deliver the full dose to the region. Since MPTB is aggressive and therefore delivery of the full dose is needed, a bolus may be beneficial for patients with MPTB. This case report is, to our knowledge, the first to mention a young adult with MPTB undergoing adjuvant radiotherapy with a bolus. A 23‐year‐old white female presented with a fibroepithelial neoplasm in her right lateral breast with no history of breast surgery, biopsy, or radiation and no skin changes, nipple discharge, or inversion. The patient underwent a skin‐ and nipple‐sparing simple mastectomy of the right breast due to residual MPTB from the prior lumpectomy. She received 5,000 cGy in 25 fractions (19 fractions without bolus and 6 fractions with 0.5 cm bolus) to the right chest wall, followed by a 1,000 cGy boost in 5 fractions using Volumetric Modulated Arc Therapy. A bolus was used for 6 of the fractions since it was difficult to give the full dose to her close margin due to the tissue expander making a portion of the concerning region flat on the chest wall. Radiotherapy was well‐tolerated, with side effects of soreness, itchiness, Grade 2 radiation dermatitis, skin hyperpigmentation, dry desquamation, and fatigue as side effects. Therefore, due to the risk of LR, her high‐risk factors, potential risk of metastasis, and difficulties to deliver full dose due to body habitus and tissue expander location, this patient benefitted from adjuvant radiotherapy using a bolus. Furthermore, this case report adds to the scarce literature of young adults with MPTB, particularly on the use of a bolus for adjuvant radiotherapy.