Young Adult With Malignant Phyllodes Undergoing Adjuvant Radiotherapy With Bolus

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.