As an oncologist who specializes in prostate cancer, my treatments often work extremely well. Most of my patients have lived for years, even decades, after their diagnosis. They often die of something other than their cancer. But my treatments often have a unique side effect: They cause men to feel less like a man. And for many men, that is worse than the cancer itself.

One afternoon I saw an older man who was diagnosed with prostate cancer years ago. After having his prostate removed, he had enjoyed nearly a decade of being “cancer free.”

But upon checking his labs, I noticed that the prostate-specific antigen (PSA) — a blood marker of prostate cancer — had quadrupled over the past few months. His prostate cancer was probably back.

I explained to him that it was lucky we had caught this before his disease had spread to his bones or liver. I began to explain to him the therapy I was going to use to beat back his cancer.

“It’s called androgen deprivation therapy,” I said, “but you can call it hormone therapy.” It would cause him to experience hot flashes, fatigue and decreased sex life. But it could ensure that he never died of his cancer.

He seemed much more disappointed than when he entered. He was the sole breadwinner, the “man” of his house. He enjoyed a healthy sex life with his partner — a sex life that took years to recover after his prostate was removed many years ago.

“Can we delay it?” he said. I told him that if his PSA continued to progress, his cancer would make the androgen deprivation therapy inevitable. If we treated early, he might only be on it for six months. But if we waited and his cancer spread further, he would be on it for the rest of his life. He agreed to the therapy, and we started the next week.

A month later, I saw him again. He was having hot flashes and breast tenderness on a daily basis. He started taking two daily naps when he had never napped before. And his sex life had quickly become nonexistent.

“I didn’t know I’d feel like such crap,” he said.

These side effects are unfortunately a part of the way we treat prostate cancer, the most common cancer afflicting men (aside from skin cancers). Often, we are able to permanently eliminate the cancer by cutting out the prostate or delivering radiation to it. Those come with their own side effects: Men who receive a prostate surgery frequently are never able to achieve an erection again and have lifelong problems with incontinence. But often these side effects get better.

But if prostate cancer comes back after surgery or radiation, or if it spreads to bones or other organs, the treatment usually involves trying to reduce the overall amount of testosterone in a man’s body. Because we are so good at curing prostate cancer, we have more than 3 million prostate cancer survivors worldwide. But about one-third of them receive androgen deprivation therapy.

Prostate cancer feeds off a man’s testosterone. We have known since the 1940s that drastically reducing the amount of testosterone can result in a decrease in prostate cancer. In an earlier era, this was achieved by literally castrating men, removing their testicles much like male dogs are neutered. Thankfully, we use medicine today (pills or shots) rather than barbaric surgery to reduce a man’s testosterone; prostate cancer specialists, however, still refer to the process as castration. And, when you think about it, that’s essentially what we are doing.

But just because this castration is less morbid doesn’t mean the side effects are any less severe.

Testosterone is involved in some way in everything from bone health to libido and having an erection. It’s responsible for virility, muscle formation, sperm production and facial hair growth. It’s the hormone that makes men feel and look like men.

Eliminating testosterone does much more than just shrink prostate cancer. Prostate cancer hormone therapy causes profound fatigue and hot flashes that mimic a woman’s menopause. Because prostate cancer therapy can increase the level of estrogen in the blood, many men have embarrassing breast enlargement and tenderness that can last for life. And because bones become weaker, close to 20 percent of men suffer a serious fracture within 10 years of starting therapy.

These side effects — particularly the effects on fatigue and sex — are usually difficult for patients to fully fathom, even if I clearly say it before treatment.

The hypothetical thought of their PSA improving outweighs the hypothetical notion that they may lose their sex life or virility. The truth is, there is close to a 100 percent chance that a man will lose most or all of their sex drive during the time of androgen deprivation therapy — and for months or years after, too. But the side effects of hormone therapy are much more manageable than the well-known side effects of chemotherapy that many people experience.

All in all, it’s rare that a man would refuse to at least start hormone therapy.

Most men only fully grasp how different they feel only about a month after they start prostate cancer therapy. As their energy level goes down and once-active men become sedentary, many men have asked me why we opted to use treatment instead of just waiting to see what happens with the PSA.

One man with advanced prostate cancer even told me, “I would have preferred chemotherapy to this.”

I understand this sentiment. For many men, the thought of vomiting over a toilet or losing their hair is much more preferable to losing their muscle mass and not being able to achieve an erection.

Another issue is that it can be difficult for men to talk about problems such as breast swelling and decreased libido. Granted, some men are open with their partners about discussing prostate cancer; indeed, being married has been associated with much longer survival for men with prostate cancer.

But this support isn’t often available to men. As a male physician, I’m usually the first person they mention these symptoms to — even before their partners. Anecdotally, the strain of prostate cancer therapy often leads to a lack of communication between men and their partners — and from what I see, sometimes divorce.

For my older patient with the quickly rising PSA, we stopped his hormone therapy after six months because his PSA had returned to normal. But he never fully recovered his desire or ability to have sex. We tried a variety of medications, and even manual pumps. These worked only slightly.

At one point, he even asked me whether we could try prescribing him testosterone. It was an impossible question for me to answer: Do I give testosterone to give him back his sex life, even if it meant that his prostate cancer would almost surely come back?

There are no easy answers to these questions in prostate cancer, but we need to start addressing them.

Current innovations in prostate treatment rely on pushing hormone and similar therapies earlier — called “treatment intensification.” But as we intensify treatment, we will also intensify the castration of men. Patients and doctors need a concurrent focus on survivorship — innovations to improve treating the side effects.

One important step would be modifying our outcomes from clinical trials — which are the way that most prostate cancer therapies are approved. Most clinical trials study only short-term adverse events. But it can often take months for a man to fully lose his sexual function. We need to study these long-term effects of therapy so that we can better inform our patients.

It may be that slight benefits in survival from using androgen or other novel therapies are not going to be worth the long-term physical and emotional side effects of castrating a man.

Most of these issues hide beneath the shadows because men with prostate cancer are not open about their therapy.

The public should know about what it takes to treat the most common cancer in men — and what it takes away. Men with prostate cancer, their partners and their doctors should discuss these issues openly because some of them are addressable. As different treatment strategies emerge, I hope treating cancers such as prostate cancer will allow men to continue feeling like men.