Current National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology note that proton therapy is an effective and acceptable form of external beam radiation. The most modern form of proton therapy, known as pencil beam scanning, has facilitated treatment of complex shapes and targets and revolutionized the utilization of proton therapy for challenging sites across the body. Herein, we review several such prostate cancer cases that were referred for treatment to serve as an example of the potential of proton therapy.

CASE #1: LOCALLY ADVANCED PROSTATE CANCER WITH IMPROVED SPARING OF THE SIGMOID BOWEL.

Patient Presentation:

A 68 year old male was diagnosed with a locally advanced, very high risk, nonmetastatic prostate cancer, cT3bN0M0, Stage IIIB, based on an initial PSA 109 ng/mL, and Gleason 4+3=7 (grade group 3) with noted extraprostatic extension and seminal vesicle invasion.

Despite prostate and tumor cytoreduction with several months of neoadjuvant androgen deprivation therapy, planning with traditional photon IMRT in both the supine and prone positions was attempted by his local radiation oncologist.This was unsuccessful due to the patient’s anatomy. Excessively high and unsafe doses were noted to the low-lying sigmoid bowel which approximated the tumor involvement in the prostate and adjacently invaded seminal vesicles.

Treatment:

The patient was referred for consideration of proton therapy where it was noted that all organs at risk including the bowel and rectum were better spared with scanning beam proton therapy as noted in Figure 1.

The patient received 8 weeks of proton therapy for a total of 39 fractions in conjunction with androgen deprivation therapy. He tolerated proton therapy exceedingly well and returned to his local Urologist (or team?) for continued androgen deprivation therapy.

CASE #2: SALVAGE RADIATION TO THE PROSTATE BED AND PELVIC LYMPH NODES.

Patient Presentation:

A 73 year old male was diagnosed with a nonmetastatic, very high risk prostate cancer and elected to undergo radical prostatectomy which demonstrated pathologic Gleason 4+4=8 (grade group 4), positive margins, and seminal vesicle invasion, pT3bN0M0.

At 3 months, post-operative, his PSA was persistent at 0.2 and rose to 0.3 a few months later. He presented for salvage radiation.

Treatment:

Considering his removed prostate, consequential challenging anatomy and ongoing urinary symptoms and recovery, scanning beam proton therapy was considered. Planning with IMPT was able to better spare all of the adjacent organs at risk including the bladder, small and large bowel, and rectum, as noted in the representative dose color wash Figure 2 (right): IMPT (top) vs IMRT plan (bottom).

The patient received 8 weeks of proton therapy for a total of 39 fractions in conjunction with androgen deprivation therapy. He tolerated proton therapy exceedingly well and returned to his local Urologist (or team?) for continued androgen deprivation therapy.

CASE #3: FAVORABLE INTERMEDIATE RISK PROSTATE CANCER IN A VERY YOUNG PATIENT DECLINING SURGERY.

Patient Presentation:

A 53 year old male with a family history of prostate cancer in his father and brother, was diagnosed with a favorable intermediate risk prostate cancer, cT1cN0M0, Gleason 3+4=7 (grade group 2) in 4 out of 12 biopsy cores. After extensive discussion of his management options with his local urologist, primary care physician, and radiation oncologist, he also sought a second opinion at the Johns Hopkins Prostate Cancer Multidisciplinary Clinic at Sibley Memorial Hospital.The patient expressed an overwhelming desire to avoid surgery and any other invasive treatments.

His outside records and work-up were reviewed in real-time with Johns Hopkins prostate cancer experts in diagnostic radiology, pathology, urologic oncology, medical oncology, radiation oncology (including proton therapy), and clinical research.

Treatment:

It was anticipated that all of his normal tissues and organs at risk including the rectum would be better spared with scanning beam proton therapy plan (Figure 3), and moreover, considering the excess scatter radiation dose from photon- based IMRT, proton therapy would be the preferred option for this relatively young man to reduce the risk of radiation-related secondary malignancy over the remainder of his lifespan.

The patient received 5.5 weeks of proton therapy for a total of 28 fractions as a solo treatment without systemic therapy.The patient tolerated therapy exceedingly well with minimal effects. He was able to continue working throughout his treatment course

He eventually tolerated proton therapy exceedingly well with minimal anticipated mild urinary and bowel effects that did not require intervention or pharmacologic management. He was able to continue working and exercising throughout treatment and thereafter.

Proton Therapy Prostate Cancer Experts

Curtiland Deville, MD
Stephen Greco, MD
Daniel Song, MD