Radiotherapeutic Management of Synchronous Prostate and Rectal Cancers Using Proton Beam Therapy

Abstract

Treatment of synchronous prostate and rectal cancers is a rare yet challenging problem with compounded toxicities. We report a case of a 65-year-old man who underwent proton beam therapy (PBT) with concurrent capecitabine and hormonal therapy for his synchronously found prostate (intermediate-risk) and rectal (cT2, N2b, stage IIIB) cancers; he also received low anterior resection. Before PBT, the patient experienced hematochezia. His baseline American Urological Association symptom score was a total of 0, and he was not sexually active. He completed PBT with grade 1 acute toxicities including fatigue, nausea, and increased urinary and bowel frequencies. He also developed mild anemia (10.7), which was resolved. Subsequent surgical pathology showed a pathologic complete response in his rectum. At follow-up of 2.5 years, he remained disease-free on surveillance imaging for both malignancies and reported increased bowel urgency and frequency, minimal urinary leakage when having urgency, and peripheral neuropathy. This case, along with a succinct literature review, demonstrates that PBT can be successful in the definitive treatment of synchronous prostate and rectal cancers with minimal toxicities. Further research is required to evaluate the efficacy and side effect profiles of PBT.

Keywords: prostate; proton beam therapy; rectal; synchronous cancers.

Figure 1.

Sagittal (A) and axial (B) T1 MRI images with contrast showing a hypervascular mass involving the posterior rectum without evidence of extension into the perirectal fat (a T2 lesion). (C) Axial T2 MRI image showing a hypointense lesion in the posteromedial aspect of the peripheral zone of the mid prostate gland (organ confined and without extracapsular extension). Abbreviation: MRI, magnetic resonance imaging.

Figure 2.

Axial (A) and sagittal (B) view of the proton beam therapy plan, encompassing irradiated volumes for both prostate and rectal cancers in a 65-year-old male patient. The GTV and CTV are shown here as CTV4500 (green, elective pelvic nodal volume), CTV5000 (rectal and prostate volumes, red), CTV7800 (sequential boost volume for prostate, blue), and GTV5000 (rectal and prostate volumes, cyan). Axial (C) and sagittal (D) images represent the same view levels of an IMRT comparison plan accordingly. Abbreviations: CTV, clinical target volume; GTV, gross target volume; IMRT, intensity-modulated radiation therapy.