What is the optimal treatment for a locally advanced rectal cancer on the anterior wall abutting the prostate in a medically inoperable patient with a remote history of LDR brachytherapy for low risk prostate cancer?

I would start with chemotherapy if that is an option and tailor RT dose to some extent based on response. If there is great response even local excision can be evaluated? Rectal and urethral complications are high and I have seen patients developing these complications even with 45 to 50.4 Gy preop dose and thus need to be careful. If the patient has limited life expectancy from being medically inoperable, then that needs to be taken into account in deciding extent of treatment based on the potential for complications.

I would propose proton therapy as an option for re-irradiation. This would reduce the dose to the urethra to essentially 0. There is, of course, always a problem of the rectum and whatever max point dose was received from the LDR.

However, depending on the patient and goals of care, aggressive chemoRT with the possibility of ulceration/perforation may be preferred over the guaranteed risk of obstruction, bleeding, and tumor perforation without adequate treatment.

I recently had a case where they had prior prostate radiation. We did chemotherapy first and he had CR for 1 year. We are now offering him salvage proton re-irradiation.

These cases are, of course, complex and very much need to be decided on a case-by-case basis.

According to my colleagues who specialized in GU, the LDR monotherapy usually has a prescription dose of 125 Gy (Pd) and 145 Gy (iodine) with a rectal constraint of V100% < 1%. So, there is a relatively high point dose just posterior to the prostate but the overall dose to the entire rectum should be very low. If the patient had a post-treatment CT, then you should be able to tell what the rectum got and where.

Since this is an inoperable patient, I would deliver combined chemotherapy and chemoradiation similar to the total neoadjuvant therapy regimen.

For re-irradiation after a remote history of LDR prostate (I assume that it was 10 or 20 years ago and you don’t know how much dose the rectum got and where the high dose point was), I will d...

Thanks, @Dr. First Last. I agree that we should try to avoid re-irradiation, especially high dose re-irradiation. Starting with chemotherapy first is also what we do. If local excision is possible, we would do that too.

The RT field for re-irradiation is usually small (only cover gross tumor) to decrease the toxicities.

I like suggestions from Dr. @Dr. First Last and @Dr. First Last. We often provide pelvic radiation 45-50 Gy in conjunction with seed implant. So standard fractionation to that dose is safe. With distant history of seed implant, a dose of 50.4 to 54 Gy is reasonable at standard fractionation. I suggest:

1. Neo-adjuvant chemotherapy
2. Attempt rectal spacer implant if possible, particularly Barrigel. Small reported series and personal experience show the possibility
3. Use proton beam therapy if possible
4. Use concurrent Xeloda for sensitization effect
5. At 50.4 Gy, assess response, if higher dose is needed, I suggest use proton beam with rectal balloon and MRI planning to target or fractionated endorectal brachytherapy. There are many applicators from...

This is a complex patient, why is the patient medically inoperable? Is it co-morbidities? If so, I then am not sure if he would be eligible to get high-dose systemic therapy. Although, that would be my first choice, if he is eligible for doublet/triplet chemotherapy.

In regards to radiation, as GU/GI rad onc I have treated both rectal recurrence and prostate recurrence safely with re-irradiation. I agree with other comments that LDR does have a high point dose of radiation, but most often this high dose point is close to the apex - near the anorectal junction, where we often see rectal hump or puborectalis muscle.

I do believe, there can be creative ways to treat this patient. I would recommend a lower dose EBRT - 30.6 Gy in 17 fractions wi...