Analysis of pathological complete response (PCR) and impact of modifiable risk factors on the premature discontinuation of pertuzumab use in early stage HER-2 breast cancer: A retrospective single-institutional study.

Abstract

e12627 Background: In patients with HER-2 positive breast cancer, Pertuzumab in combination with Trastuzumab forms a potent Anti HER-2 regimen. Randomized clinical trials have concluded that addition of Pertuzumab to Trastuzumab and Chemotherapy leads to improved rates of Pathological Complete Response and also improved Invasive-disease-free survival rates in early stage HER-2 positive breast cancer. Pertuzumab is frequently associated with treatment limiting diarrhea and other adverse effects. In this study, we report our experience with the use of Pertuzumab in early stage HER-2 breast cancer. We analyzed the adverse events, PCR rates for those patients who had premature discontinuation of treatment versus those who had successful treatment completion, and modifiable risk factors that may have affected completion of treatment. Methods: We conducted an IRB approved, retrospective study, analyzing the use of Pertuzumab at our institution for early stage (Stage I-III), HER-2 positive female and male breast cancer patients seen from June 2018 to June 2022. Data were obtained from our Institutional Cancer Registry. Results: One hundred and eighteen (118) patient charts were reviewed. Sixty Five (55.08%) patients received Pertuzumab. Of the patients who received Pertuzumab, 61 (93.85%) received it in the Neoadjuvant setting. Thirty Eight (58.46%) patients completed the treatment and 27 (41.5%) patients had premature treatment discontinuation due to adverse effects. The rate of PCR in patient who completed the prescribed treatment course was 55.56%, and 51.85% for those who did not (p value 0.77). Among the patients in whom treatment was discontinued, diarrhea (51%), followed by rash (11.11%) were the main adverse effects. Almost 66% of non-smokers completed treatment as compared to 48% of smokers (p value 0.15). Patients with a normal BMI had a treatment completion rate of 76% compared to obese or overweight patients who had a rate of 52% (p value 0.08). Conclusions: Our retrospective study showed that there was a high premature discontinuation rate of the use of Pertuzumab. This is due to adverse effects, diarrhea being the most notable. However, the PCR rate difference was not statistically significant (55.56 vs 51.85, P value 0.77) in patients who completed treatment versus those who did not. There was a positive trend observed that non-smokers and non-obese patients were more likely to complete treatment with Pertuzumab. Although it was observed that premature discontinuation of Pertuzumab did not significantly impact PCR, further studies are required to validate this observation.