Chemotherapy remains a core component of systemic therapy for breast cancer. Typical adverse effects include nausea, vomiting, diarrhea, and myelosuppression. By contrast, chemotherapy-induced colitis is uncommon and its pathophysiology is not well defined. This case report describes an instance of colitis and subsequent colonic ulceration occurring during adjuvant combination chemotherapy for HER2-positive invasive breast cancer, and outlines a practical approach to regimen modification.
The patient was a 53-year-old woman who had undergone left total mastectomy for invasive breast carcinoma staged as pT2N0M0 (Stage IIA). Tumor receptor status was reported as estrogen receptor–negative, progesterone receptor–negative, and HER2 3+. She commenced adjuvant chemotherapy using the TCbHP protocol, consisting of docetaxel, carboplatin, trastuzumab, and pertuzumab.
One week after the first cycle of TCbHP the patient developed abdominal pain and diarrhea. Those new gastrointestinal symptoms prompted endoscopic evaluation.
Colonoscopy performed after the onset of symptoms demonstrated findings consistent with colitis. The report does not provide detailed microbiological, histopathological, or imaging data in the source abstract beyond the colonoscopic diagnosis. After the second cycle (administered at a reduced dose of 80%), recurrent abdominal pain led to repeat colonoscopy, which revealed colonic ulcers.
Because the patient had received combination chemotherapy, the source states that a definitive causal link to any single agent could not be determined from this report. The mechanism underlying chemotherapy-associated colitis in this case was not clarified in the abstract and is described generally as unclear.
Following detection of colonic ulcers after the second reduced-dose cycle, the treatment team modified the chemotherapy regimen. They replaced the TCbHP protocol with a THP regimen composed of nab-paclitaxel (albumin-bound paclitaxel), trastuzumab, and pertuzumab. The change eliminated docetaxel and carboplatin from the combination while continuing dual anti-HER2 antibody therapy.
The source abstract indicates that this regimen modification was associated with clinical improvement. Specific supportive care measures, antimicrobial testing, use of corticosteroids, or other adjunctive interventions are not detailed in the abstract.
After switching to THP, the patient’s abdominal pain and diarrhea resolved. Follow-up colonoscopy documented healing of the previously observed colonic ulcers. The authors note that timely intervention and regimen modification in this case appeared to prevent progression to severe complications such as intestinal necrosis or the need for bowel resection.
This case highlights several clinical considerations:
Chemotherapy-associated colitis is an uncommon but clinically important adverse event. It may present shortly after administration of cytotoxic agents and targeted antibodies and can progress to ulceration or necrosis if not recognized and managed.
Combination regimens complicate attribution of causality. In this patient, TCbHP includes docetaxel and carboplatin in addition to the monoclonal antibodies trastuzumab and pertuzumab; any of these agents, alone or in combination, might have contributed, but the single-case design prevents definitive determination.
Dose reduction alone did not prevent disease progression in this instance; despite a reduced dose (80%) in the second cycle, colitis recurred with ulceration. Changing the cytotoxic backbone from docetaxel/carboplatin to nab-paclitaxel while maintaining anti-HER2 therapy corresponded to symptom resolution and mucosal healing.
The report underscores the importance of prompt endoscopic assessment when patients on chemotherapy develop abdominal pain and diarrhea, and of considering chemotherapy modification to prevent severe gastrointestinal complications.
Limitations reported by the authors include the single-case design and lack of causality proof; details such as histology, infectious workup, and specific management steps beyond regimen change were not reported in the abstract.
Colitis following breast cancer chemotherapy is rare but can be serious. In this reported case of a 53-year-old woman receiving adjuvant TCbHP, colonoscopy-confirmed colitis and subsequent ulceration occurred early in the treatment course. Regimen modification to THP (nab-paclitaxel with trastuzumab and pertuzumab) was followed by symptom resolution and endoscopic healing. The case suggests that timely recognition and pragmatic alteration of the chemotherapy regimen may prevent progression to intestinal necrosis, though a causal relationship to a specific agent cannot be established from a single case report.
Reference information available in the source: Am J Case Rep. 2026; DOI 10.12659/AJCR.952507; PMID 42571049.